linux/mm/kmemleak.c
Waiman Long e68d343d27 mm/kmemleak: move up cond_resched() call in page scanning loop
Commit bde5f6bc68 ("kmemleak: add scheduling point to kmemleak_scan()")
added a cond_resched() call to the struct page scanning loop to prevent
soft lockup from happening.  However, soft lockup can still happen in that
loop in some corner cases when the pages that satisfy the "!(pfn & 63)"
check are skipped for some reasons.

Fix this corner case by moving up the cond_resched() check so that it will
be called every 64 pages unconditionally.

Link: https://lkml.kernel.org/r/20230825164947.1317981-1-longman@redhat.com
Fixes: bde5f6bc68 ("kmemleak: add scheduling point to kmemleak_scan()")
Signed-off-by: Waiman Long <longman@redhat.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Yisheng Xie <xieyisheng1@huawei.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
2023-09-02 15:17:34 -07:00

2153 lines
61 KiB
C

// SPDX-License-Identifier: GPL-2.0-only
/*
* mm/kmemleak.c
*
* Copyright (C) 2008 ARM Limited
* Written by Catalin Marinas <catalin.marinas@arm.com>
*
* For more information on the algorithm and kmemleak usage, please see
* Documentation/dev-tools/kmemleak.rst.
*
* Notes on locking
* ----------------
*
* The following locks and mutexes are used by kmemleak:
*
* - kmemleak_lock (raw_spinlock_t): protects the object_list as well as
* del_state modifications and accesses to the object_tree_root (or
* object_phys_tree_root). The object_list is the main list holding the
* metadata (struct kmemleak_object) for the allocated memory blocks.
* The object_tree_root and object_phys_tree_root are red
* black trees used to look-up metadata based on a pointer to the
* corresponding memory block. The object_phys_tree_root is for objects
* allocated with physical address. The kmemleak_object structures are
* added to the object_list and object_tree_root (or object_phys_tree_root)
* in the create_object() function called from the kmemleak_alloc() (or
* kmemleak_alloc_phys()) callback and removed in delete_object() called from
* the kmemleak_free() callback
* - kmemleak_object.lock (raw_spinlock_t): protects a kmemleak_object.
* Accesses to the metadata (e.g. count) are protected by this lock. Note
* that some members of this structure may be protected by other means
* (atomic or kmemleak_lock). This lock is also held when scanning the
* corresponding memory block to avoid the kernel freeing it via the
* kmemleak_free() callback. This is less heavyweight than holding a global
* lock like kmemleak_lock during scanning.
* - scan_mutex (mutex): ensures that only one thread may scan the memory for
* unreferenced objects at a time. The gray_list contains the objects which
* are already referenced or marked as false positives and need to be
* scanned. This list is only modified during a scanning episode when the
* scan_mutex is held. At the end of a scan, the gray_list is always empty.
* Note that the kmemleak_object.use_count is incremented when an object is
* added to the gray_list and therefore cannot be freed. This mutex also
* prevents multiple users of the "kmemleak" debugfs file together with
* modifications to the memory scanning parameters including the scan_thread
* pointer
*
* Locks and mutexes are acquired/nested in the following order:
*
* scan_mutex [-> object->lock] -> kmemleak_lock -> other_object->lock (SINGLE_DEPTH_NESTING)
*
* No kmemleak_lock and object->lock nesting is allowed outside scan_mutex
* regions.
*
* The kmemleak_object structures have a use_count incremented or decremented
* using the get_object()/put_object() functions. When the use_count becomes
* 0, this count can no longer be incremented and put_object() schedules the
* kmemleak_object freeing via an RCU callback. All calls to the get_object()
* function must be protected by rcu_read_lock() to avoid accessing a freed
* structure.
*/
#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/list.h>
#include <linux/sched/signal.h>
#include <linux/sched/task.h>
#include <linux/sched/task_stack.h>
#include <linux/jiffies.h>
#include <linux/delay.h>
#include <linux/export.h>
#include <linux/kthread.h>
#include <linux/rbtree.h>
#include <linux/fs.h>
#include <linux/debugfs.h>
#include <linux/seq_file.h>
#include <linux/cpumask.h>
#include <linux/spinlock.h>
#include <linux/module.h>
#include <linux/mutex.h>
#include <linux/rcupdate.h>
#include <linux/stacktrace.h>
#include <linux/stackdepot.h>
#include <linux/cache.h>
#include <linux/percpu.h>
#include <linux/memblock.h>
#include <linux/pfn.h>
#include <linux/mmzone.h>
#include <linux/slab.h>
#include <linux/thread_info.h>
#include <linux/err.h>
#include <linux/uaccess.h>
#include <linux/string.h>
#include <linux/nodemask.h>
#include <linux/mm.h>
#include <linux/workqueue.h>
#include <linux/crc32.h>
#include <asm/sections.h>
#include <asm/processor.h>
#include <linux/atomic.h>
#include <linux/kasan.h>
#include <linux/kfence.h>
#include <linux/kmemleak.h>
#include <linux/memory_hotplug.h>
/*
* Kmemleak configuration and common defines.
*/
#define MAX_TRACE 16 /* stack trace length */
#define MSECS_MIN_AGE 5000 /* minimum object age for reporting */
#define SECS_FIRST_SCAN 60 /* delay before the first scan */
#define SECS_SCAN_WAIT 600 /* subsequent auto scanning delay */
#define MAX_SCAN_SIZE 4096 /* maximum size of a scanned block */
#define BYTES_PER_POINTER sizeof(void *)
/* GFP bitmask for kmemleak internal allocations */
#define gfp_kmemleak_mask(gfp) (((gfp) & (GFP_KERNEL | GFP_ATOMIC | \
__GFP_NOLOCKDEP)) | \
__GFP_NORETRY | __GFP_NOMEMALLOC | \
__GFP_NOWARN)
/* scanning area inside a memory block */
struct kmemleak_scan_area {
struct hlist_node node;
unsigned long start;
size_t size;
};
#define KMEMLEAK_GREY 0
#define KMEMLEAK_BLACK -1
/*
* Structure holding the metadata for each allocated memory block.
* Modifications to such objects should be made while holding the
* object->lock. Insertions or deletions from object_list, gray_list or
* rb_node are already protected by the corresponding locks or mutex (see
* the notes on locking above). These objects are reference-counted
* (use_count) and freed using the RCU mechanism.
*/
struct kmemleak_object {
raw_spinlock_t lock;
unsigned int flags; /* object status flags */
struct list_head object_list;
struct list_head gray_list;
struct rb_node rb_node;
struct rcu_head rcu; /* object_list lockless traversal */
/* object usage count; object freed when use_count == 0 */
atomic_t use_count;
unsigned int del_state; /* deletion state */
unsigned long pointer;
size_t size;
/* pass surplus references to this pointer */
unsigned long excess_ref;
/* minimum number of a pointers found before it is considered leak */
int min_count;
/* the total number of pointers found pointing to this object */
int count;
/* checksum for detecting modified objects */
u32 checksum;
/* memory ranges to be scanned inside an object (empty for all) */
struct hlist_head area_list;
depot_stack_handle_t trace_handle;
unsigned long jiffies; /* creation timestamp */
pid_t pid; /* pid of the current task */
char comm[TASK_COMM_LEN]; /* executable name */
};
/* flag representing the memory block allocation status */
#define OBJECT_ALLOCATED (1 << 0)
/* flag set after the first reporting of an unreference object */
#define OBJECT_REPORTED (1 << 1)
/* flag set to not scan the object */
#define OBJECT_NO_SCAN (1 << 2)
/* flag set to fully scan the object when scan_area allocation failed */
#define OBJECT_FULL_SCAN (1 << 3)
/* flag set for object allocated with physical address */
#define OBJECT_PHYS (1 << 4)
/* set when __remove_object() called */
#define DELSTATE_REMOVED (1 << 0)
/* set to temporarily prevent deletion from object_list */
#define DELSTATE_NO_DELETE (1 << 1)
#define HEX_PREFIX " "
/* number of bytes to print per line; must be 16 or 32 */
#define HEX_ROW_SIZE 16
/* number of bytes to print at a time (1, 2, 4, 8) */
#define HEX_GROUP_SIZE 1
/* include ASCII after the hex output */
#define HEX_ASCII 1
/* max number of lines to be printed */
#define HEX_MAX_LINES 2
/* the list of all allocated objects */
static LIST_HEAD(object_list);
/* the list of gray-colored objects (see color_gray comment below) */
static LIST_HEAD(gray_list);
/* memory pool allocation */
static struct kmemleak_object mem_pool[CONFIG_DEBUG_KMEMLEAK_MEM_POOL_SIZE];
static int mem_pool_free_count = ARRAY_SIZE(mem_pool);
static LIST_HEAD(mem_pool_free_list);
/* search tree for object boundaries */
static struct rb_root object_tree_root = RB_ROOT;
/* search tree for object (with OBJECT_PHYS flag) boundaries */
static struct rb_root object_phys_tree_root = RB_ROOT;
/* protecting the access to object_list, object_tree_root (or object_phys_tree_root) */
static DEFINE_RAW_SPINLOCK(kmemleak_lock);
/* allocation caches for kmemleak internal data */
static struct kmem_cache *object_cache;
static struct kmem_cache *scan_area_cache;
/* set if tracing memory operations is enabled */
static int kmemleak_enabled = 1;
/* same as above but only for the kmemleak_free() callback */
static int kmemleak_free_enabled = 1;
/* set in the late_initcall if there were no errors */
static int kmemleak_late_initialized;
/* set if a kmemleak warning was issued */
static int kmemleak_warning;
/* set if a fatal kmemleak error has occurred */
static int kmemleak_error;
/* minimum and maximum address that may be valid pointers */
static unsigned long min_addr = ULONG_MAX;
static unsigned long max_addr;
static struct task_struct *scan_thread;
/* used to avoid reporting of recently allocated objects */
static unsigned long jiffies_min_age;
static unsigned long jiffies_last_scan;
/* delay between automatic memory scannings */
static unsigned long jiffies_scan_wait;
/* enables or disables the task stacks scanning */
static int kmemleak_stack_scan = 1;
/* protects the memory scanning, parameters and debug/kmemleak file access */
static DEFINE_MUTEX(scan_mutex);
/* setting kmemleak=on, will set this var, skipping the disable */
static int kmemleak_skip_disable;
/* If there are leaks that can be reported */
static bool kmemleak_found_leaks;
static bool kmemleak_verbose;
module_param_named(verbose, kmemleak_verbose, bool, 0600);
static void kmemleak_disable(void);
/*
* Print a warning and dump the stack trace.
*/
#define kmemleak_warn(x...) do { \
pr_warn(x); \
dump_stack(); \
kmemleak_warning = 1; \
} while (0)
/*
* Macro invoked when a serious kmemleak condition occurred and cannot be
* recovered from. Kmemleak will be disabled and further allocation/freeing
* tracing no longer available.
*/
#define kmemleak_stop(x...) do { \
kmemleak_warn(x); \
kmemleak_disable(); \
} while (0)
#define warn_or_seq_printf(seq, fmt, ...) do { \
if (seq) \
seq_printf(seq, fmt, ##__VA_ARGS__); \
else \
pr_warn(fmt, ##__VA_ARGS__); \
} while (0)
static void warn_or_seq_hex_dump(struct seq_file *seq, int prefix_type,
int rowsize, int groupsize, const void *buf,
size_t len, bool ascii)
{
if (seq)
seq_hex_dump(seq, HEX_PREFIX, prefix_type, rowsize, groupsize,
buf, len, ascii);
else
print_hex_dump(KERN_WARNING, pr_fmt(HEX_PREFIX), prefix_type,
rowsize, groupsize, buf, len, ascii);
}
/*
* Printing of the objects hex dump to the seq file. The number of lines to be
* printed is limited to HEX_MAX_LINES to prevent seq file spamming. The
* actual number of printed bytes depends on HEX_ROW_SIZE. It must be called
* with the object->lock held.
*/
static void hex_dump_object(struct seq_file *seq,
struct kmemleak_object *object)
{
const u8 *ptr = (const u8 *)object->pointer;
size_t len;
if (WARN_ON_ONCE(object->flags & OBJECT_PHYS))
return;
/* limit the number of lines to HEX_MAX_LINES */
len = min_t(size_t, object->size, HEX_MAX_LINES * HEX_ROW_SIZE);
warn_or_seq_printf(seq, " hex dump (first %zu bytes):\n", len);
kasan_disable_current();
warn_or_seq_hex_dump(seq, DUMP_PREFIX_NONE, HEX_ROW_SIZE,
HEX_GROUP_SIZE, kasan_reset_tag((void *)ptr), len, HEX_ASCII);
kasan_enable_current();
}
/*
* Object colors, encoded with count and min_count:
* - white - orphan object, not enough references to it (count < min_count)
* - gray - not orphan, not marked as false positive (min_count == 0) or
* sufficient references to it (count >= min_count)
* - black - ignore, it doesn't contain references (e.g. text section)
* (min_count == -1). No function defined for this color.
* Newly created objects don't have any color assigned (object->count == -1)
* before the next memory scan when they become white.
*/
static bool color_white(const struct kmemleak_object *object)
{
return object->count != KMEMLEAK_BLACK &&
object->count < object->min_count;
}
static bool color_gray(const struct kmemleak_object *object)
{
return object->min_count != KMEMLEAK_BLACK &&
object->count >= object->min_count;
}
/*
* Objects are considered unreferenced only if their color is white, they have
* not be deleted and have a minimum age to avoid false positives caused by
* pointers temporarily stored in CPU registers.
*/
static bool unreferenced_object(struct kmemleak_object *object)
{
return (color_white(object) && object->flags & OBJECT_ALLOCATED) &&
time_before_eq(object->jiffies + jiffies_min_age,
jiffies_last_scan);
}
/*
* Printing of the unreferenced objects information to the seq file. The
* print_unreferenced function must be called with the object->lock held.
*/
static void print_unreferenced(struct seq_file *seq,
struct kmemleak_object *object)
{
int i;
unsigned long *entries;
unsigned int nr_entries;
unsigned int msecs_age = jiffies_to_msecs(jiffies - object->jiffies);
nr_entries = stack_depot_fetch(object->trace_handle, &entries);
warn_or_seq_printf(seq, "unreferenced object 0x%08lx (size %zu):\n",
object->pointer, object->size);
warn_or_seq_printf(seq, " comm \"%s\", pid %d, jiffies %lu (age %d.%03ds)\n",
object->comm, object->pid, object->jiffies,
msecs_age / 1000, msecs_age % 1000);
hex_dump_object(seq, object);
warn_or_seq_printf(seq, " backtrace:\n");
for (i = 0; i < nr_entries; i++) {
void *ptr = (void *)entries[i];
warn_or_seq_printf(seq, " [<%pK>] %pS\n", ptr, ptr);
}
}
/*
* Print the kmemleak_object information. This function is used mainly for
* debugging special cases when kmemleak operations. It must be called with
* the object->lock held.
*/
static void dump_object_info(struct kmemleak_object *object)
{
pr_notice("Object 0x%08lx (size %zu):\n",
object->pointer, object->size);
pr_notice(" comm \"%s\", pid %d, jiffies %lu\n",
object->comm, object->pid, object->jiffies);
pr_notice(" min_count = %d\n", object->min_count);
pr_notice(" count = %d\n", object->count);
pr_notice(" flags = 0x%x\n", object->flags);
pr_notice(" checksum = %u\n", object->checksum);
pr_notice(" backtrace:\n");
if (object->trace_handle)
stack_depot_print(object->trace_handle);
}
/*
* Look-up a memory block metadata (kmemleak_object) in the object search
* tree based on a pointer value. If alias is 0, only values pointing to the
* beginning of the memory block are allowed. The kmemleak_lock must be held
* when calling this function.
*/
static struct kmemleak_object *__lookup_object(unsigned long ptr, int alias,
bool is_phys)
{
struct rb_node *rb = is_phys ? object_phys_tree_root.rb_node :
object_tree_root.rb_node;
unsigned long untagged_ptr = (unsigned long)kasan_reset_tag((void *)ptr);
while (rb) {
struct kmemleak_object *object;
unsigned long untagged_objp;
object = rb_entry(rb, struct kmemleak_object, rb_node);
untagged_objp = (unsigned long)kasan_reset_tag((void *)object->pointer);
if (untagged_ptr < untagged_objp)
rb = object->rb_node.rb_left;
else if (untagged_objp + object->size <= untagged_ptr)
rb = object->rb_node.rb_right;
else if (untagged_objp == untagged_ptr || alias)
return object;
else {
kmemleak_warn("Found object by alias at 0x%08lx\n",
ptr);
dump_object_info(object);
break;
}
}
return NULL;
}
/* Look-up a kmemleak object which allocated with virtual address. */
static struct kmemleak_object *lookup_object(unsigned long ptr, int alias)
{
return __lookup_object(ptr, alias, false);
}
/*
* Increment the object use_count. Return 1 if successful or 0 otherwise. Note
* that once an object's use_count reached 0, the RCU freeing was already
* registered and the object should no longer be used. This function must be
* called under the protection of rcu_read_lock().
*/
static int get_object(struct kmemleak_object *object)
{
return atomic_inc_not_zero(&object->use_count);
}
/*
* Memory pool allocation and freeing. kmemleak_lock must not be held.
*/
static struct kmemleak_object *mem_pool_alloc(gfp_t gfp)
{
unsigned long flags;
struct kmemleak_object *object;
/* try the slab allocator first */
if (object_cache) {
object = kmem_cache_alloc(object_cache, gfp_kmemleak_mask(gfp));
if (object)
return object;
}
/* slab allocation failed, try the memory pool */
raw_spin_lock_irqsave(&kmemleak_lock, flags);
object = list_first_entry_or_null(&mem_pool_free_list,
typeof(*object), object_list);
if (object)
list_del(&object->object_list);
else if (mem_pool_free_count)
object = &mem_pool[--mem_pool_free_count];
else
pr_warn_once("Memory pool empty, consider increasing CONFIG_DEBUG_KMEMLEAK_MEM_POOL_SIZE\n");
raw_spin_unlock_irqrestore(&kmemleak_lock, flags);
return object;
}
/*
* Return the object to either the slab allocator or the memory pool.
*/
static void mem_pool_free(struct kmemleak_object *object)
{
unsigned long flags;
if (object < mem_pool || object >= mem_pool + ARRAY_SIZE(mem_pool)) {
kmem_cache_free(object_cache, object);
return;
}
/* add the object to the memory pool free list */
raw_spin_lock_irqsave(&kmemleak_lock, flags);
list_add(&object->object_list, &mem_pool_free_list);
raw_spin_unlock_irqrestore(&kmemleak_lock, flags);
}
/*
* RCU callback to free a kmemleak_object.
*/
static void free_object_rcu(struct rcu_head *rcu)
{
struct hlist_node *tmp;
struct kmemleak_scan_area *area;
struct kmemleak_object *object =
container_of(rcu, struct kmemleak_object, rcu);
/*
* Once use_count is 0 (guaranteed by put_object), there is no other
* code accessing this object, hence no need for locking.
*/
hlist_for_each_entry_safe(area, tmp, &object->area_list, node) {
hlist_del(&area->node);
kmem_cache_free(scan_area_cache, area);
}
mem_pool_free(object);
}
/*
* Decrement the object use_count. Once the count is 0, free the object using
* an RCU callback. Since put_object() may be called via the kmemleak_free() ->
* delete_object() path, the delayed RCU freeing ensures that there is no
* recursive call to the kernel allocator. Lock-less RCU object_list traversal
* is also possible.
*/
static void put_object(struct kmemleak_object *object)
{
if (!atomic_dec_and_test(&object->use_count))
return;
/* should only get here after delete_object was called */
WARN_ON(object->flags & OBJECT_ALLOCATED);
/*
* It may be too early for the RCU callbacks, however, there is no
* concurrent object_list traversal when !object_cache and all objects
* came from the memory pool. Free the object directly.
*/
if (object_cache)
call_rcu(&object->rcu, free_object_rcu);
else
free_object_rcu(&object->rcu);
}
/*
* Look up an object in the object search tree and increase its use_count.
*/
static struct kmemleak_object *__find_and_get_object(unsigned long ptr, int alias,
bool is_phys)
{
unsigned long flags;
struct kmemleak_object *object;
rcu_read_lock();
raw_spin_lock_irqsave(&kmemleak_lock, flags);
object = __lookup_object(ptr, alias, is_phys);
raw_spin_unlock_irqrestore(&kmemleak_lock, flags);
/* check whether the object is still available */
if (object && !get_object(object))
object = NULL;
rcu_read_unlock();
return object;
}
/* Look up and get an object which allocated with virtual address. */
static struct kmemleak_object *find_and_get_object(unsigned long ptr, int alias)
{
return __find_and_get_object(ptr, alias, false);
}
/*
* Remove an object from the object_tree_root (or object_phys_tree_root)
* and object_list. Must be called with the kmemleak_lock held _if_ kmemleak
* is still enabled.
*/
static void __remove_object(struct kmemleak_object *object)
{
rb_erase(&object->rb_node, object->flags & OBJECT_PHYS ?
&object_phys_tree_root :
&object_tree_root);
if (!(object->del_state & DELSTATE_NO_DELETE))
list_del_rcu(&object->object_list);
object->del_state |= DELSTATE_REMOVED;
}
/*
* Look up an object in the object search tree and remove it from both
* object_tree_root (or object_phys_tree_root) and object_list. The
* returned object's use_count should be at least 1, as initially set
* by create_object().
*/
static struct kmemleak_object *find_and_remove_object(unsigned long ptr, int alias,
bool is_phys)
{
unsigned long flags;
struct kmemleak_object *object;
raw_spin_lock_irqsave(&kmemleak_lock, flags);
object = __lookup_object(ptr, alias, is_phys);
if (object)
__remove_object(object);
raw_spin_unlock_irqrestore(&kmemleak_lock, flags);
return object;
}
static noinline depot_stack_handle_t set_track_prepare(void)
{
depot_stack_handle_t trace_handle;
unsigned long entries[MAX_TRACE];
unsigned int nr_entries;
/*
* Use object_cache to determine whether kmemleak_init() has
* been invoked. stack_depot_early_init() is called before
* kmemleak_init() in mm_core_init().
*/
if (!object_cache)
return 0;
nr_entries = stack_trace_save(entries, ARRAY_SIZE(entries), 3);
trace_handle = stack_depot_save(entries, nr_entries, GFP_NOWAIT);
return trace_handle;
}
/*
* Create the metadata (struct kmemleak_object) corresponding to an allocated
* memory block and add it to the object_list and object_tree_root (or
* object_phys_tree_root).
*/
static void __create_object(unsigned long ptr, size_t size,
int min_count, gfp_t gfp, bool is_phys)
{
unsigned long flags;
struct kmemleak_object *object, *parent;
struct rb_node **link, *rb_parent;
unsigned long untagged_ptr;
unsigned long untagged_objp;
object = mem_pool_alloc(gfp);
if (!object) {
pr_warn("Cannot allocate a kmemleak_object structure\n");
kmemleak_disable();
return;
}
INIT_LIST_HEAD(&object->object_list);
INIT_LIST_HEAD(&object->gray_list);
INIT_HLIST_HEAD(&object->area_list);
raw_spin_lock_init(&object->lock);
atomic_set(&object->use_count, 1);
object->flags = OBJECT_ALLOCATED | (is_phys ? OBJECT_PHYS : 0);
object->pointer = ptr;
object->size = kfence_ksize((void *)ptr) ?: size;
object->excess_ref = 0;
object->min_count = min_count;
object->count = 0; /* white color initially */
object->jiffies = jiffies;
object->checksum = 0;
object->del_state = 0;
/* task information */
if (in_hardirq()) {
object->pid = 0;
strncpy(object->comm, "hardirq", sizeof(object->comm));
} else if (in_serving_softirq()) {
object->pid = 0;
strncpy(object->comm, "softirq", sizeof(object->comm));
} else {
object->pid = current->pid;
/*
* There is a small chance of a race with set_task_comm(),
* however using get_task_comm() here may cause locking
* dependency issues with current->alloc_lock. In the worst
* case, the command line is not correct.
*/
strncpy(object->comm, current->comm, sizeof(object->comm));
}
/* kernel backtrace */
object->trace_handle = set_track_prepare();
raw_spin_lock_irqsave(&kmemleak_lock, flags);
untagged_ptr = (unsigned long)kasan_reset_tag((void *)ptr);
/*
* Only update min_addr and max_addr with object
* storing virtual address.
*/
if (!is_phys) {
min_addr = min(min_addr, untagged_ptr);
max_addr = max(max_addr, untagged_ptr + size);
}
link = is_phys ? &object_phys_tree_root.rb_node :
&object_tree_root.rb_node;
rb_parent = NULL;
while (*link) {
rb_parent = *link;
parent = rb_entry(rb_parent, struct kmemleak_object, rb_node);
untagged_objp = (unsigned long)kasan_reset_tag((void *)parent->pointer);
if (untagged_ptr + size <= untagged_objp)
link = &parent->rb_node.rb_left;
else if (untagged_objp + parent->size <= untagged_ptr)
link = &parent->rb_node.rb_right;
else {
kmemleak_stop("Cannot insert 0x%lx into the object search tree (overlaps existing)\n",
ptr);
/*
* No need for parent->lock here since "parent" cannot
* be freed while the kmemleak_lock is held.
*/
dump_object_info(parent);
kmem_cache_free(object_cache, object);
goto out;
}
}
rb_link_node(&object->rb_node, rb_parent, link);
rb_insert_color(&object->rb_node, is_phys ? &object_phys_tree_root :
&object_tree_root);
list_add_tail_rcu(&object->object_list, &object_list);
out:
raw_spin_unlock_irqrestore(&kmemleak_lock, flags);
}
/* Create kmemleak object which allocated with virtual address. */
static void create_object(unsigned long ptr, size_t size,
int min_count, gfp_t gfp)
{
__create_object(ptr, size, min_count, gfp, false);
}
/* Create kmemleak object which allocated with physical address. */
static void create_object_phys(unsigned long ptr, size_t size,
int min_count, gfp_t gfp)
{
__create_object(ptr, size, min_count, gfp, true);
}
/*
* Mark the object as not allocated and schedule RCU freeing via put_object().
*/
static void __delete_object(struct kmemleak_object *object)
{
unsigned long flags;
WARN_ON(!(object->flags & OBJECT_ALLOCATED));
WARN_ON(atomic_read(&object->use_count) < 1);
/*
* Locking here also ensures that the corresponding memory block
* cannot be freed when it is being scanned.
*/
raw_spin_lock_irqsave(&object->lock, flags);
object->flags &= ~OBJECT_ALLOCATED;
raw_spin_unlock_irqrestore(&object->lock, flags);
put_object(object);
}
/*
* Look up the metadata (struct kmemleak_object) corresponding to ptr and
* delete it.
*/
static void delete_object_full(unsigned long ptr)
{
struct kmemleak_object *object;
object = find_and_remove_object(ptr, 0, false);
if (!object) {
#ifdef DEBUG
kmemleak_warn("Freeing unknown object at 0x%08lx\n",
ptr);
#endif
return;
}
__delete_object(object);
}
/*
* Look up the metadata (struct kmemleak_object) corresponding to ptr and
* delete it. If the memory block is partially freed, the function may create
* additional metadata for the remaining parts of the block.
*/
static void delete_object_part(unsigned long ptr, size_t size, bool is_phys)
{
struct kmemleak_object *object;
unsigned long start, end;
object = find_and_remove_object(ptr, 1, is_phys);
if (!object) {
#ifdef DEBUG
kmemleak_warn("Partially freeing unknown object at 0x%08lx (size %zu)\n",
ptr, size);
#endif
return;
}
/*
* Create one or two objects that may result from the memory block
* split. Note that partial freeing is only done by free_bootmem() and
* this happens before kmemleak_init() is called.
*/
start = object->pointer;
end = object->pointer + object->size;
if (ptr > start)
__create_object(start, ptr - start, object->min_count,
GFP_KERNEL, is_phys);
if (ptr + size < end)
__create_object(ptr + size, end - ptr - size, object->min_count,
GFP_KERNEL, is_phys);
__delete_object(object);
}
static void __paint_it(struct kmemleak_object *object, int color)
{
object->min_count = color;
if (color == KMEMLEAK_BLACK)
object->flags |= OBJECT_NO_SCAN;
}
static void paint_it(struct kmemleak_object *object, int color)
{
unsigned long flags;
raw_spin_lock_irqsave(&object->lock, flags);
__paint_it(object, color);
raw_spin_unlock_irqrestore(&object->lock, flags);
}
static void paint_ptr(unsigned long ptr, int color, bool is_phys)
{
struct kmemleak_object *object;
object = __find_and_get_object(ptr, 0, is_phys);
if (!object) {
kmemleak_warn("Trying to color unknown object at 0x%08lx as %s\n",
ptr,
(color == KMEMLEAK_GREY) ? "Grey" :
(color == KMEMLEAK_BLACK) ? "Black" : "Unknown");
return;
}
paint_it(object, color);
put_object(object);
}
/*
* Mark an object permanently as gray-colored so that it can no longer be
* reported as a leak. This is used in general to mark a false positive.
*/
static void make_gray_object(unsigned long ptr)
{
paint_ptr(ptr, KMEMLEAK_GREY, false);
}
/*
* Mark the object as black-colored so that it is ignored from scans and
* reporting.
*/
static void make_black_object(unsigned long ptr, bool is_phys)
{
paint_ptr(ptr, KMEMLEAK_BLACK, is_phys);
}
/*
* Add a scanning area to the object. If at least one such area is added,
* kmemleak will only scan these ranges rather than the whole memory block.
*/
static void add_scan_area(unsigned long ptr, size_t size, gfp_t gfp)
{
unsigned long flags;
struct kmemleak_object *object;
struct kmemleak_scan_area *area = NULL;
unsigned long untagged_ptr;
unsigned long untagged_objp;
object = find_and_get_object(ptr, 1);
if (!object) {
kmemleak_warn("Adding scan area to unknown object at 0x%08lx\n",
ptr);
return;
}
untagged_ptr = (unsigned long)kasan_reset_tag((void *)ptr);
untagged_objp = (unsigned long)kasan_reset_tag((void *)object->pointer);
if (scan_area_cache)
area = kmem_cache_alloc(scan_area_cache, gfp_kmemleak_mask(gfp));
raw_spin_lock_irqsave(&object->lock, flags);
if (!area) {
pr_warn_once("Cannot allocate a scan area, scanning the full object\n");
/* mark the object for full scan to avoid false positives */
object->flags |= OBJECT_FULL_SCAN;
goto out_unlock;
}
if (size == SIZE_MAX) {
size = untagged_objp + object->size - untagged_ptr;
} else if (untagged_ptr + size > untagged_objp + object->size) {
kmemleak_warn("Scan area larger than object 0x%08lx\n", ptr);
dump_object_info(object);
kmem_cache_free(scan_area_cache, area);
goto out_unlock;
}
INIT_HLIST_NODE(&area->node);
area->start = ptr;
area->size = size;
hlist_add_head(&area->node, &object->area_list);
out_unlock:
raw_spin_unlock_irqrestore(&object->lock, flags);
put_object(object);
}
/*
* Any surplus references (object already gray) to 'ptr' are passed to
* 'excess_ref'. This is used in the vmalloc() case where a pointer to
* vm_struct may be used as an alternative reference to the vmalloc'ed object
* (see free_thread_stack()).
*/
static void object_set_excess_ref(unsigned long ptr, unsigned long excess_ref)
{
unsigned long flags;
struct kmemleak_object *object;
object = find_and_get_object(ptr, 0);
if (!object) {
kmemleak_warn("Setting excess_ref on unknown object at 0x%08lx\n",
ptr);
return;
}
raw_spin_lock_irqsave(&object->lock, flags);
object->excess_ref = excess_ref;
raw_spin_unlock_irqrestore(&object->lock, flags);
put_object(object);
}
/*
* Set the OBJECT_NO_SCAN flag for the object corresponding to the give
* pointer. Such object will not be scanned by kmemleak but references to it
* are searched.
*/
static void object_no_scan(unsigned long ptr)
{
unsigned long flags;
struct kmemleak_object *object;
object = find_and_get_object(ptr, 0);
if (!object) {
kmemleak_warn("Not scanning unknown object at 0x%08lx\n", ptr);
return;
}
raw_spin_lock_irqsave(&object->lock, flags);
object->flags |= OBJECT_NO_SCAN;
raw_spin_unlock_irqrestore(&object->lock, flags);
put_object(object);
}
/**
* kmemleak_alloc - register a newly allocated object
* @ptr: pointer to beginning of the object
* @size: size of the object
* @min_count: minimum number of references to this object. If during memory
* scanning a number of references less than @min_count is found,
* the object is reported as a memory leak. If @min_count is 0,
* the object is never reported as a leak. If @min_count is -1,
* the object is ignored (not scanned and not reported as a leak)
* @gfp: kmalloc() flags used for kmemleak internal memory allocations
*
* This function is called from the kernel allocators when a new object
* (memory block) is allocated (kmem_cache_alloc, kmalloc etc.).
*/
void __ref kmemleak_alloc(const void *ptr, size_t size, int min_count,
gfp_t gfp)
{
pr_debug("%s(0x%p, %zu, %d)\n", __func__, ptr, size, min_count);
if (kmemleak_enabled && ptr && !IS_ERR(ptr))
create_object((unsigned long)ptr, size, min_count, gfp);
}
EXPORT_SYMBOL_GPL(kmemleak_alloc);
/**
* kmemleak_alloc_percpu - register a newly allocated __percpu object
* @ptr: __percpu pointer to beginning of the object
* @size: size of the object
* @gfp: flags used for kmemleak internal memory allocations
*
* This function is called from the kernel percpu allocator when a new object
* (memory block) is allocated (alloc_percpu).
*/
void __ref kmemleak_alloc_percpu(const void __percpu *ptr, size_t size,
gfp_t gfp)
{
unsigned int cpu;
pr_debug("%s(0x%p, %zu)\n", __func__, ptr, size);
/*
* Percpu allocations are only scanned and not reported as leaks
* (min_count is set to 0).
*/
if (kmemleak_enabled && ptr && !IS_ERR(ptr))
for_each_possible_cpu(cpu)
create_object((unsigned long)per_cpu_ptr(ptr, cpu),
size, 0, gfp);
}
EXPORT_SYMBOL_GPL(kmemleak_alloc_percpu);
/**
* kmemleak_vmalloc - register a newly vmalloc'ed object
* @area: pointer to vm_struct
* @size: size of the object
* @gfp: __vmalloc() flags used for kmemleak internal memory allocations
*
* This function is called from the vmalloc() kernel allocator when a new
* object (memory block) is allocated.
*/
void __ref kmemleak_vmalloc(const struct vm_struct *area, size_t size, gfp_t gfp)
{
pr_debug("%s(0x%p, %zu)\n", __func__, area, size);
/*
* A min_count = 2 is needed because vm_struct contains a reference to
* the virtual address of the vmalloc'ed block.
*/
if (kmemleak_enabled) {
create_object((unsigned long)area->addr, size, 2, gfp);
object_set_excess_ref((unsigned long)area,
(unsigned long)area->addr);
}
}
EXPORT_SYMBOL_GPL(kmemleak_vmalloc);
/**
* kmemleak_free - unregister a previously registered object
* @ptr: pointer to beginning of the object
*
* This function is called from the kernel allocators when an object (memory
* block) is freed (kmem_cache_free, kfree, vfree etc.).
*/
void __ref kmemleak_free(const void *ptr)
{
pr_debug("%s(0x%p)\n", __func__, ptr);
if (kmemleak_free_enabled && ptr && !IS_ERR(ptr))
delete_object_full((unsigned long)ptr);
}
EXPORT_SYMBOL_GPL(kmemleak_free);
/**
* kmemleak_free_part - partially unregister a previously registered object
* @ptr: pointer to the beginning or inside the object. This also
* represents the start of the range to be freed
* @size: size to be unregistered
*
* This function is called when only a part of a memory block is freed
* (usually from the bootmem allocator).
*/
void __ref kmemleak_free_part(const void *ptr, size_t size)
{
pr_debug("%s(0x%p)\n", __func__, ptr);
if (kmemleak_enabled && ptr && !IS_ERR(ptr))
delete_object_part((unsigned long)ptr, size, false);
}
EXPORT_SYMBOL_GPL(kmemleak_free_part);
/**
* kmemleak_free_percpu - unregister a previously registered __percpu object
* @ptr: __percpu pointer to beginning of the object
*
* This function is called from the kernel percpu allocator when an object
* (memory block) is freed (free_percpu).
*/
void __ref kmemleak_free_percpu(const void __percpu *ptr)
{
unsigned int cpu;
pr_debug("%s(0x%p)\n", __func__, ptr);
if (kmemleak_free_enabled && ptr && !IS_ERR(ptr))
for_each_possible_cpu(cpu)
delete_object_full((unsigned long)per_cpu_ptr(ptr,
cpu));
}
EXPORT_SYMBOL_GPL(kmemleak_free_percpu);
/**
* kmemleak_update_trace - update object allocation stack trace
* @ptr: pointer to beginning of the object
*
* Override the object allocation stack trace for cases where the actual
* allocation place is not always useful.
*/
void __ref kmemleak_update_trace(const void *ptr)
{
struct kmemleak_object *object;
unsigned long flags;
pr_debug("%s(0x%p)\n", __func__, ptr);
if (!kmemleak_enabled || IS_ERR_OR_NULL(ptr))
return;
object = find_and_get_object((unsigned long)ptr, 1);
if (!object) {
#ifdef DEBUG
kmemleak_warn("Updating stack trace for unknown object at %p\n",
ptr);
#endif
return;
}
raw_spin_lock_irqsave(&object->lock, flags);
object->trace_handle = set_track_prepare();
raw_spin_unlock_irqrestore(&object->lock, flags);
put_object(object);
}
EXPORT_SYMBOL(kmemleak_update_trace);
/**
* kmemleak_not_leak - mark an allocated object as false positive
* @ptr: pointer to beginning of the object
*
* Calling this function on an object will cause the memory block to no longer
* be reported as leak and always be scanned.
*/
void __ref kmemleak_not_leak(const void *ptr)
{
pr_debug("%s(0x%p)\n", __func__, ptr);
if (kmemleak_enabled && ptr && !IS_ERR(ptr))
make_gray_object((unsigned long)ptr);
}
EXPORT_SYMBOL(kmemleak_not_leak);
/**
* kmemleak_ignore - ignore an allocated object
* @ptr: pointer to beginning of the object
*
* Calling this function on an object will cause the memory block to be
* ignored (not scanned and not reported as a leak). This is usually done when
* it is known that the corresponding block is not a leak and does not contain
* any references to other allocated memory blocks.
*/
void __ref kmemleak_ignore(const void *ptr)
{
pr_debug("%s(0x%p)\n", __func__, ptr);
if (kmemleak_enabled && ptr && !IS_ERR(ptr))
make_black_object((unsigned long)ptr, false);
}
EXPORT_SYMBOL(kmemleak_ignore);
/**
* kmemleak_scan_area - limit the range to be scanned in an allocated object
* @ptr: pointer to beginning or inside the object. This also
* represents the start of the scan area
* @size: size of the scan area
* @gfp: kmalloc() flags used for kmemleak internal memory allocations
*
* This function is used when it is known that only certain parts of an object
* contain references to other objects. Kmemleak will only scan these areas
* reducing the number false negatives.
*/
void __ref kmemleak_scan_area(const void *ptr, size_t size, gfp_t gfp)
{
pr_debug("%s(0x%p)\n", __func__, ptr);
if (kmemleak_enabled && ptr && size && !IS_ERR(ptr))
add_scan_area((unsigned long)ptr, size, gfp);
}
EXPORT_SYMBOL(kmemleak_scan_area);
/**
* kmemleak_no_scan - do not scan an allocated object
* @ptr: pointer to beginning of the object
*
* This function notifies kmemleak not to scan the given memory block. Useful
* in situations where it is known that the given object does not contain any
* references to other objects. Kmemleak will not scan such objects reducing
* the number of false negatives.
*/
void __ref kmemleak_no_scan(const void *ptr)
{
pr_debug("%s(0x%p)\n", __func__, ptr);
if (kmemleak_enabled && ptr && !IS_ERR(ptr))
object_no_scan((unsigned long)ptr);
}
EXPORT_SYMBOL(kmemleak_no_scan);
/**
* kmemleak_alloc_phys - similar to kmemleak_alloc but taking a physical
* address argument
* @phys: physical address of the object
* @size: size of the object
* @gfp: kmalloc() flags used for kmemleak internal memory allocations
*/
void __ref kmemleak_alloc_phys(phys_addr_t phys, size_t size, gfp_t gfp)
{
pr_debug("%s(0x%pa, %zu)\n", __func__, &phys, size);
if (kmemleak_enabled)
/*
* Create object with OBJECT_PHYS flag and
* assume min_count 0.
*/
create_object_phys((unsigned long)phys, size, 0, gfp);
}
EXPORT_SYMBOL(kmemleak_alloc_phys);
/**
* kmemleak_free_part_phys - similar to kmemleak_free_part but taking a
* physical address argument
* @phys: physical address if the beginning or inside an object. This
* also represents the start of the range to be freed
* @size: size to be unregistered
*/
void __ref kmemleak_free_part_phys(phys_addr_t phys, size_t size)
{
pr_debug("%s(0x%pa)\n", __func__, &phys);
if (kmemleak_enabled)
delete_object_part((unsigned long)phys, size, true);
}
EXPORT_SYMBOL(kmemleak_free_part_phys);
/**
* kmemleak_ignore_phys - similar to kmemleak_ignore but taking a physical
* address argument
* @phys: physical address of the object
*/
void __ref kmemleak_ignore_phys(phys_addr_t phys)
{
pr_debug("%s(0x%pa)\n", __func__, &phys);
if (kmemleak_enabled)
make_black_object((unsigned long)phys, true);
}
EXPORT_SYMBOL(kmemleak_ignore_phys);
/*
* Update an object's checksum and return true if it was modified.
*/
static bool update_checksum(struct kmemleak_object *object)
{
u32 old_csum = object->checksum;
if (WARN_ON_ONCE(object->flags & OBJECT_PHYS))
return false;
kasan_disable_current();
kcsan_disable_current();
object->checksum = crc32(0, kasan_reset_tag((void *)object->pointer), object->size);
kasan_enable_current();
kcsan_enable_current();
return object->checksum != old_csum;
}
/*
* Update an object's references. object->lock must be held by the caller.
*/
static void update_refs(struct kmemleak_object *object)
{
if (!color_white(object)) {
/* non-orphan, ignored or new */
return;
}
/*
* Increase the object's reference count (number of pointers to the
* memory block). If this count reaches the required minimum, the
* object's color will become gray and it will be added to the
* gray_list.
*/
object->count++;
if (color_gray(object)) {
/* put_object() called when removing from gray_list */
WARN_ON(!get_object(object));
list_add_tail(&object->gray_list, &gray_list);
}
}
/*
* Memory scanning is a long process and it needs to be interruptible. This
* function checks whether such interrupt condition occurred.
*/
static int scan_should_stop(void)
{
if (!kmemleak_enabled)
return 1;
/*
* This function may be called from either process or kthread context,
* hence the need to check for both stop conditions.
*/
if (current->mm)
return signal_pending(current);
else
return kthread_should_stop();
return 0;
}
/*
* Scan a memory block (exclusive range) for valid pointers and add those
* found to the gray list.
*/
static void scan_block(void *_start, void *_end,
struct kmemleak_object *scanned)
{
unsigned long *ptr;
unsigned long *start = PTR_ALIGN(_start, BYTES_PER_POINTER);
unsigned long *end = _end - (BYTES_PER_POINTER - 1);
unsigned long flags;
unsigned long untagged_ptr;
raw_spin_lock_irqsave(&kmemleak_lock, flags);
for (ptr = start; ptr < end; ptr++) {
struct kmemleak_object *object;
unsigned long pointer;
unsigned long excess_ref;
if (scan_should_stop())
break;
kasan_disable_current();
pointer = *(unsigned long *)kasan_reset_tag((void *)ptr);
kasan_enable_current();
untagged_ptr = (unsigned long)kasan_reset_tag((void *)pointer);
if (untagged_ptr < min_addr || untagged_ptr >= max_addr)
continue;
/*
* No need for get_object() here since we hold kmemleak_lock.
* object->use_count cannot be dropped to 0 while the object
* is still present in object_tree_root and object_list
* (with updates protected by kmemleak_lock).
*/
object = lookup_object(pointer, 1);
if (!object)
continue;
if (object == scanned)
/* self referenced, ignore */
continue;
/*
* Avoid the lockdep recursive warning on object->lock being
* previously acquired in scan_object(). These locks are
* enclosed by scan_mutex.
*/
raw_spin_lock_nested(&object->lock, SINGLE_DEPTH_NESTING);
/* only pass surplus references (object already gray) */
if (color_gray(object)) {
excess_ref = object->excess_ref;
/* no need for update_refs() if object already gray */
} else {
excess_ref = 0;
update_refs(object);
}
raw_spin_unlock(&object->lock);
if (excess_ref) {
object = lookup_object(excess_ref, 0);
if (!object)
continue;
if (object == scanned)
/* circular reference, ignore */
continue;
raw_spin_lock_nested(&object->lock, SINGLE_DEPTH_NESTING);
update_refs(object);
raw_spin_unlock(&object->lock);
}
}
raw_spin_unlock_irqrestore(&kmemleak_lock, flags);
}
/*
* Scan a large memory block in MAX_SCAN_SIZE chunks to reduce the latency.
*/
#ifdef CONFIG_SMP
static void scan_large_block(void *start, void *end)
{
void *next;
while (start < end) {
next = min(start + MAX_SCAN_SIZE, end);
scan_block(start, next, NULL);
start = next;
cond_resched();
}
}
#endif
/*
* Scan a memory block corresponding to a kmemleak_object. A condition is
* that object->use_count >= 1.
*/
static void scan_object(struct kmemleak_object *object)
{
struct kmemleak_scan_area *area;
unsigned long flags;
void *obj_ptr;
/*
* Once the object->lock is acquired, the corresponding memory block
* cannot be freed (the same lock is acquired in delete_object).
*/
raw_spin_lock_irqsave(&object->lock, flags);
if (object->flags & OBJECT_NO_SCAN)
goto out;
if (!(object->flags & OBJECT_ALLOCATED))
/* already freed object */
goto out;
obj_ptr = object->flags & OBJECT_PHYS ?
__va((phys_addr_t)object->pointer) :
(void *)object->pointer;
if (hlist_empty(&object->area_list) ||
object->flags & OBJECT_FULL_SCAN) {
void *start = obj_ptr;
void *end = obj_ptr + object->size;
void *next;
do {
next = min(start + MAX_SCAN_SIZE, end);
scan_block(start, next, object);
start = next;
if (start >= end)
break;
raw_spin_unlock_irqrestore(&object->lock, flags);
cond_resched();
raw_spin_lock_irqsave(&object->lock, flags);
} while (object->flags & OBJECT_ALLOCATED);
} else
hlist_for_each_entry(area, &object->area_list, node)
scan_block((void *)area->start,
(void *)(area->start + area->size),
object);
out:
raw_spin_unlock_irqrestore(&object->lock, flags);
}
/*
* Scan the objects already referenced (gray objects). More objects will be
* referenced and, if there are no memory leaks, all the objects are scanned.
*/
static void scan_gray_list(void)
{
struct kmemleak_object *object, *tmp;
/*
* The list traversal is safe for both tail additions and removals
* from inside the loop. The kmemleak objects cannot be freed from
* outside the loop because their use_count was incremented.
*/
object = list_entry(gray_list.next, typeof(*object), gray_list);
while (&object->gray_list != &gray_list) {
cond_resched();
/* may add new objects to the list */
if (!scan_should_stop())
scan_object(object);
tmp = list_entry(object->gray_list.next, typeof(*object),
gray_list);
/* remove the object from the list and release it */
list_del(&object->gray_list);
put_object(object);
object = tmp;
}
WARN_ON(!list_empty(&gray_list));
}
/*
* Conditionally call resched() in an object iteration loop while making sure
* that the given object won't go away without RCU read lock by performing a
* get_object() if necessaary.
*/
static void kmemleak_cond_resched(struct kmemleak_object *object)
{
if (!get_object(object))
return; /* Try next object */
raw_spin_lock_irq(&kmemleak_lock);
if (object->del_state & DELSTATE_REMOVED)
goto unlock_put; /* Object removed */
object->del_state |= DELSTATE_NO_DELETE;
raw_spin_unlock_irq(&kmemleak_lock);
rcu_read_unlock();
cond_resched();
rcu_read_lock();
raw_spin_lock_irq(&kmemleak_lock);
if (object->del_state & DELSTATE_REMOVED)
list_del_rcu(&object->object_list);
object->del_state &= ~DELSTATE_NO_DELETE;
unlock_put:
raw_spin_unlock_irq(&kmemleak_lock);
put_object(object);
}
/*
* Scan data sections and all the referenced memory blocks allocated via the
* kernel's standard allocators. This function must be called with the
* scan_mutex held.
*/
static void kmemleak_scan(void)
{
struct kmemleak_object *object;
struct zone *zone;
int __maybe_unused i;
int new_leaks = 0;
jiffies_last_scan = jiffies;
/* prepare the kmemleak_object's */
rcu_read_lock();
list_for_each_entry_rcu(object, &object_list, object_list) {
raw_spin_lock_irq(&object->lock);
#ifdef DEBUG
/*
* With a few exceptions there should be a maximum of
* 1 reference to any object at this point.
*/
if (atomic_read(&object->use_count) > 1) {
pr_debug("object->use_count = %d\n",
atomic_read(&object->use_count));
dump_object_info(object);
}
#endif
/* ignore objects outside lowmem (paint them black) */
if ((object->flags & OBJECT_PHYS) &&
!(object->flags & OBJECT_NO_SCAN)) {
unsigned long phys = object->pointer;
if (PHYS_PFN(phys) < min_low_pfn ||
PHYS_PFN(phys + object->size) >= max_low_pfn)
__paint_it(object, KMEMLEAK_BLACK);
}
/* reset the reference count (whiten the object) */
object->count = 0;
if (color_gray(object) && get_object(object))
list_add_tail(&object->gray_list, &gray_list);
raw_spin_unlock_irq(&object->lock);
if (need_resched())
kmemleak_cond_resched(object);
}
rcu_read_unlock();
#ifdef CONFIG_SMP
/* per-cpu sections scanning */
for_each_possible_cpu(i)
scan_large_block(__per_cpu_start + per_cpu_offset(i),
__per_cpu_end + per_cpu_offset(i));
#endif
/*
* Struct page scanning for each node.
*/
get_online_mems();
for_each_populated_zone(zone) {
unsigned long start_pfn = zone->zone_start_pfn;
unsigned long end_pfn = zone_end_pfn(zone);
unsigned long pfn;
for (pfn = start_pfn; pfn < end_pfn; pfn++) {
struct page *page = pfn_to_online_page(pfn);
if (!(pfn & 63))
cond_resched();
if (!page)
continue;
/* only scan pages belonging to this zone */
if (page_zone(page) != zone)
continue;
/* only scan if page is in use */
if (page_count(page) == 0)
continue;
scan_block(page, page + 1, NULL);
}
}
put_online_mems();
/*
* Scanning the task stacks (may introduce false negatives).
*/
if (kmemleak_stack_scan) {
struct task_struct *p, *g;
rcu_read_lock();
for_each_process_thread(g, p) {
void *stack = try_get_task_stack(p);
if (stack) {
scan_block(stack, stack + THREAD_SIZE, NULL);
put_task_stack(p);
}
}
rcu_read_unlock();
}
/*
* Scan the objects already referenced from the sections scanned
* above.
*/
scan_gray_list();
/*
* Check for new or unreferenced objects modified since the previous
* scan and color them gray until the next scan.
*/
rcu_read_lock();
list_for_each_entry_rcu(object, &object_list, object_list) {
if (need_resched())
kmemleak_cond_resched(object);
/*
* This is racy but we can save the overhead of lock/unlock
* calls. The missed objects, if any, should be caught in
* the next scan.
*/
if (!color_white(object))
continue;
raw_spin_lock_irq(&object->lock);
if (color_white(object) && (object->flags & OBJECT_ALLOCATED)
&& update_checksum(object) && get_object(object)) {
/* color it gray temporarily */
object->count = object->min_count;
list_add_tail(&object->gray_list, &gray_list);
}
raw_spin_unlock_irq(&object->lock);
}
rcu_read_unlock();
/*
* Re-scan the gray list for modified unreferenced objects.
*/
scan_gray_list();
/*
* If scanning was stopped do not report any new unreferenced objects.
*/
if (scan_should_stop())
return;
/*
* Scanning result reporting.
*/
rcu_read_lock();
list_for_each_entry_rcu(object, &object_list, object_list) {
if (need_resched())
kmemleak_cond_resched(object);
/*
* This is racy but we can save the overhead of lock/unlock
* calls. The missed objects, if any, should be caught in
* the next scan.
*/
if (!color_white(object))
continue;
raw_spin_lock_irq(&object->lock);
if (unreferenced_object(object) &&
!(object->flags & OBJECT_REPORTED)) {
object->flags |= OBJECT_REPORTED;
if (kmemleak_verbose)
print_unreferenced(NULL, object);
new_leaks++;
}
raw_spin_unlock_irq(&object->lock);
}
rcu_read_unlock();
if (new_leaks) {
kmemleak_found_leaks = true;
pr_info("%d new suspected memory leaks (see /sys/kernel/debug/kmemleak)\n",
new_leaks);
}
}
/*
* Thread function performing automatic memory scanning. Unreferenced objects
* at the end of a memory scan are reported but only the first time.
*/
static int kmemleak_scan_thread(void *arg)
{
static int first_run = IS_ENABLED(CONFIG_DEBUG_KMEMLEAK_AUTO_SCAN);
pr_info("Automatic memory scanning thread started\n");
set_user_nice(current, 10);
/*
* Wait before the first scan to allow the system to fully initialize.
*/
if (first_run) {
signed long timeout = msecs_to_jiffies(SECS_FIRST_SCAN * 1000);
first_run = 0;
while (timeout && !kthread_should_stop())
timeout = schedule_timeout_interruptible(timeout);
}
while (!kthread_should_stop()) {
signed long timeout = READ_ONCE(jiffies_scan_wait);
mutex_lock(&scan_mutex);
kmemleak_scan();
mutex_unlock(&scan_mutex);
/* wait before the next scan */
while (timeout && !kthread_should_stop())
timeout = schedule_timeout_interruptible(timeout);
}
pr_info("Automatic memory scanning thread ended\n");
return 0;
}
/*
* Start the automatic memory scanning thread. This function must be called
* with the scan_mutex held.
*/
static void start_scan_thread(void)
{
if (scan_thread)
return;
scan_thread = kthread_run(kmemleak_scan_thread, NULL, "kmemleak");
if (IS_ERR(scan_thread)) {
pr_warn("Failed to create the scan thread\n");
scan_thread = NULL;
}
}
/*
* Stop the automatic memory scanning thread.
*/
static void stop_scan_thread(void)
{
if (scan_thread) {
kthread_stop(scan_thread);
scan_thread = NULL;
}
}
/*
* Iterate over the object_list and return the first valid object at or after
* the required position with its use_count incremented. The function triggers
* a memory scanning when the pos argument points to the first position.
*/
static void *kmemleak_seq_start(struct seq_file *seq, loff_t *pos)
{
struct kmemleak_object *object;
loff_t n = *pos;
int err;
err = mutex_lock_interruptible(&scan_mutex);
if (err < 0)
return ERR_PTR(err);
rcu_read_lock();
list_for_each_entry_rcu(object, &object_list, object_list) {
if (n-- > 0)
continue;
if (get_object(object))
goto out;
}
object = NULL;
out:
return object;
}
/*
* Return the next object in the object_list. The function decrements the
* use_count of the previous object and increases that of the next one.
*/
static void *kmemleak_seq_next(struct seq_file *seq, void *v, loff_t *pos)
{
struct kmemleak_object *prev_obj = v;
struct kmemleak_object *next_obj = NULL;
struct kmemleak_object *obj = prev_obj;
++(*pos);
list_for_each_entry_continue_rcu(obj, &object_list, object_list) {
if (get_object(obj)) {
next_obj = obj;
break;
}
}
put_object(prev_obj);
return next_obj;
}
/*
* Decrement the use_count of the last object required, if any.
*/
static void kmemleak_seq_stop(struct seq_file *seq, void *v)
{
if (!IS_ERR(v)) {
/*
* kmemleak_seq_start may return ERR_PTR if the scan_mutex
* waiting was interrupted, so only release it if !IS_ERR.
*/
rcu_read_unlock();
mutex_unlock(&scan_mutex);
if (v)
put_object(v);
}
}
/*
* Print the information for an unreferenced object to the seq file.
*/
static int kmemleak_seq_show(struct seq_file *seq, void *v)
{
struct kmemleak_object *object = v;
unsigned long flags;
raw_spin_lock_irqsave(&object->lock, flags);
if ((object->flags & OBJECT_REPORTED) && unreferenced_object(object))
print_unreferenced(seq, object);
raw_spin_unlock_irqrestore(&object->lock, flags);
return 0;
}
static const struct seq_operations kmemleak_seq_ops = {
.start = kmemleak_seq_start,
.next = kmemleak_seq_next,
.stop = kmemleak_seq_stop,
.show = kmemleak_seq_show,
};
static int kmemleak_open(struct inode *inode, struct file *file)
{
return seq_open(file, &kmemleak_seq_ops);
}
static int dump_str_object_info(const char *str)
{
unsigned long flags;
struct kmemleak_object *object;
unsigned long addr;
if (kstrtoul(str, 0, &addr))
return -EINVAL;
object = find_and_get_object(addr, 0);
if (!object) {
pr_info("Unknown object at 0x%08lx\n", addr);
return -EINVAL;
}
raw_spin_lock_irqsave(&object->lock, flags);
dump_object_info(object);
raw_spin_unlock_irqrestore(&object->lock, flags);
put_object(object);
return 0;
}
/*
* We use grey instead of black to ensure we can do future scans on the same
* objects. If we did not do future scans these black objects could
* potentially contain references to newly allocated objects in the future and
* we'd end up with false positives.
*/
static void kmemleak_clear(void)
{
struct kmemleak_object *object;
rcu_read_lock();
list_for_each_entry_rcu(object, &object_list, object_list) {
raw_spin_lock_irq(&object->lock);
if ((object->flags & OBJECT_REPORTED) &&
unreferenced_object(object))
__paint_it(object, KMEMLEAK_GREY);
raw_spin_unlock_irq(&object->lock);
}
rcu_read_unlock();
kmemleak_found_leaks = false;
}
static void __kmemleak_do_cleanup(void);
/*
* File write operation to configure kmemleak at run-time. The following
* commands can be written to the /sys/kernel/debug/kmemleak file:
* off - disable kmemleak (irreversible)
* stack=on - enable the task stacks scanning
* stack=off - disable the tasks stacks scanning
* scan=on - start the automatic memory scanning thread
* scan=off - stop the automatic memory scanning thread
* scan=... - set the automatic memory scanning period in seconds (0 to
* disable it)
* scan - trigger a memory scan
* clear - mark all current reported unreferenced kmemleak objects as
* grey to ignore printing them, or free all kmemleak objects
* if kmemleak has been disabled.
* dump=... - dump information about the object found at the given address
*/
static ssize_t kmemleak_write(struct file *file, const char __user *user_buf,
size_t size, loff_t *ppos)
{
char buf[64];
int buf_size;
int ret;
buf_size = min(size, (sizeof(buf) - 1));
if (strncpy_from_user(buf, user_buf, buf_size) < 0)
return -EFAULT;
buf[buf_size] = 0;
ret = mutex_lock_interruptible(&scan_mutex);
if (ret < 0)
return ret;
if (strncmp(buf, "clear", 5) == 0) {
if (kmemleak_enabled)
kmemleak_clear();
else
__kmemleak_do_cleanup();
goto out;
}
if (!kmemleak_enabled) {
ret = -EPERM;
goto out;
}
if (strncmp(buf, "off", 3) == 0)
kmemleak_disable();
else if (strncmp(buf, "stack=on", 8) == 0)
kmemleak_stack_scan = 1;
else if (strncmp(buf, "stack=off", 9) == 0)
kmemleak_stack_scan = 0;
else if (strncmp(buf, "scan=on", 7) == 0)
start_scan_thread();
else if (strncmp(buf, "scan=off", 8) == 0)
stop_scan_thread();
else if (strncmp(buf, "scan=", 5) == 0) {
unsigned secs;
unsigned long msecs;
ret = kstrtouint(buf + 5, 0, &secs);
if (ret < 0)
goto out;
msecs = secs * MSEC_PER_SEC;
if (msecs > UINT_MAX)
msecs = UINT_MAX;
stop_scan_thread();
if (msecs) {
WRITE_ONCE(jiffies_scan_wait, msecs_to_jiffies(msecs));
start_scan_thread();
}
} else if (strncmp(buf, "scan", 4) == 0)
kmemleak_scan();
else if (strncmp(buf, "dump=", 5) == 0)
ret = dump_str_object_info(buf + 5);
else
ret = -EINVAL;
out:
mutex_unlock(&scan_mutex);
if (ret < 0)
return ret;
/* ignore the rest of the buffer, only one command at a time */
*ppos += size;
return size;
}
static const struct file_operations kmemleak_fops = {
.owner = THIS_MODULE,
.open = kmemleak_open,
.read = seq_read,
.write = kmemleak_write,
.llseek = seq_lseek,
.release = seq_release,
};
static void __kmemleak_do_cleanup(void)
{
struct kmemleak_object *object, *tmp;
/*
* Kmemleak has already been disabled, no need for RCU list traversal
* or kmemleak_lock held.
*/
list_for_each_entry_safe(object, tmp, &object_list, object_list) {
__remove_object(object);
__delete_object(object);
}
}
/*
* Stop the memory scanning thread and free the kmemleak internal objects if
* no previous scan thread (otherwise, kmemleak may still have some useful
* information on memory leaks).
*/
static void kmemleak_do_cleanup(struct work_struct *work)
{
stop_scan_thread();
mutex_lock(&scan_mutex);
/*
* Once it is made sure that kmemleak_scan has stopped, it is safe to no
* longer track object freeing. Ordering of the scan thread stopping and
* the memory accesses below is guaranteed by the kthread_stop()
* function.
*/
kmemleak_free_enabled = 0;
mutex_unlock(&scan_mutex);
if (!kmemleak_found_leaks)
__kmemleak_do_cleanup();
else
pr_info("Kmemleak disabled without freeing internal data. Reclaim the memory with \"echo clear > /sys/kernel/debug/kmemleak\".\n");
}
static DECLARE_WORK(cleanup_work, kmemleak_do_cleanup);
/*
* Disable kmemleak. No memory allocation/freeing will be traced once this
* function is called. Disabling kmemleak is an irreversible operation.
*/
static void kmemleak_disable(void)
{
/* atomically check whether it was already invoked */
if (cmpxchg(&kmemleak_error, 0, 1))
return;
/* stop any memory operation tracing */
kmemleak_enabled = 0;
/* check whether it is too early for a kernel thread */
if (kmemleak_late_initialized)
schedule_work(&cleanup_work);
else
kmemleak_free_enabled = 0;
pr_info("Kernel memory leak detector disabled\n");
}
/*
* Allow boot-time kmemleak disabling (enabled by default).
*/
static int __init kmemleak_boot_config(char *str)
{
if (!str)
return -EINVAL;
if (strcmp(str, "off") == 0)
kmemleak_disable();
else if (strcmp(str, "on") == 0) {
kmemleak_skip_disable = 1;
stack_depot_request_early_init();
}
else
return -EINVAL;
return 0;
}
early_param("kmemleak", kmemleak_boot_config);
/*
* Kmemleak initialization.
*/
void __init kmemleak_init(void)
{
#ifdef CONFIG_DEBUG_KMEMLEAK_DEFAULT_OFF
if (!kmemleak_skip_disable) {
kmemleak_disable();
return;
}
#endif
if (kmemleak_error)
return;
jiffies_min_age = msecs_to_jiffies(MSECS_MIN_AGE);
jiffies_scan_wait = msecs_to_jiffies(SECS_SCAN_WAIT * 1000);
object_cache = KMEM_CACHE(kmemleak_object, SLAB_NOLEAKTRACE);
scan_area_cache = KMEM_CACHE(kmemleak_scan_area, SLAB_NOLEAKTRACE);
/* register the data/bss sections */
create_object((unsigned long)_sdata, _edata - _sdata,
KMEMLEAK_GREY, GFP_ATOMIC);
create_object((unsigned long)__bss_start, __bss_stop - __bss_start,
KMEMLEAK_GREY, GFP_ATOMIC);
/* only register .data..ro_after_init if not within .data */
if (&__start_ro_after_init < &_sdata || &__end_ro_after_init > &_edata)
create_object((unsigned long)__start_ro_after_init,
__end_ro_after_init - __start_ro_after_init,
KMEMLEAK_GREY, GFP_ATOMIC);
}
/*
* Late initialization function.
*/
static int __init kmemleak_late_init(void)
{
kmemleak_late_initialized = 1;
debugfs_create_file("kmemleak", 0644, NULL, NULL, &kmemleak_fops);
if (kmemleak_error) {
/*
* Some error occurred and kmemleak was disabled. There is a
* small chance that kmemleak_disable() was called immediately
* after setting kmemleak_late_initialized and we may end up with
* two clean-up threads but serialized by scan_mutex.
*/
schedule_work(&cleanup_work);
return -ENOMEM;
}
if (IS_ENABLED(CONFIG_DEBUG_KMEMLEAK_AUTO_SCAN)) {
mutex_lock(&scan_mutex);
start_scan_thread();
mutex_unlock(&scan_mutex);
}
pr_info("Kernel memory leak detector initialized (mem pool available: %d)\n",
mem_pool_free_count);
return 0;
}
late_initcall(kmemleak_late_init);