linux/drivers/base/devcoredump.c
Greg Kroah-Hartman 75a2d4226b driver core: class: mark the struct class for sysfs callbacks as constant
struct class should never be modified in a sysfs callback as there is
nothing in the structure to modify, and frankly, the structure is almost
never used in a sysfs callback, so mark it as constant to allow struct
class to be moved to read-only memory.

While we are touching all class sysfs callbacks also mark the attribute
as constant as it can not be modified.  The bonding code still uses this
structure so it can not be removed from the function callbacks.

Cc: "David S. Miller" <davem@davemloft.net>
Cc: "Rafael J. Wysocki" <rafael@kernel.org>
Cc: Bartosz Golaszewski <brgl@bgdev.pl>
Cc: Eric Dumazet <edumazet@google.com>
Cc: Jakub Kicinski <kuba@kernel.org>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Johannes Berg <johannes@sipsolutions.net>
Cc: Linus Walleij <linus.walleij@linaro.org>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Miquel Raynal <miquel.raynal@bootlin.com>
Cc: Namjae Jeon <linkinjeon@kernel.org>
Cc: Paolo Abeni <pabeni@redhat.com>
Cc: Russ Weight <russell.h.weight@intel.com>
Cc: Sergey Senozhatsky <senozhatsky@chromium.org>
Cc: Steve French <sfrench@samba.org>
Cc: Vignesh Raghavendra <vigneshr@ti.com>
Cc: linux-cifs@vger.kernel.org
Cc: linux-gpio@vger.kernel.org
Cc: linux-mtd@lists.infradead.org
Cc: linux-rdma@vger.kernel.org
Cc: linux-s390@vger.kernel.org
Cc: linuxppc-dev@lists.ozlabs.org
Cc: netdev@vger.kernel.org
Reviewed-by: Luis Chamberlain <mcgrof@kernel.org>
Link: https://lore.kernel.org/r/20230325084537.3622280-1-gregkh@linuxfoundation.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2023-03-29 07:54:58 +02:00

426 lines
12 KiB
C

// SPDX-License-Identifier: GPL-2.0
/*
* Copyright(c) 2014 Intel Mobile Communications GmbH
* Copyright(c) 2015 Intel Deutschland GmbH
*
* Author: Johannes Berg <johannes@sipsolutions.net>
*/
#include <linux/module.h>
#include <linux/device.h>
#include <linux/devcoredump.h>
#include <linux/list.h>
#include <linux/slab.h>
#include <linux/fs.h>
#include <linux/workqueue.h>
static struct class devcd_class;
/* global disable flag, for security purposes */
static bool devcd_disabled;
/* if data isn't read by userspace after 5 minutes then delete it */
#define DEVCD_TIMEOUT (HZ * 60 * 5)
struct devcd_entry {
struct device devcd_dev;
void *data;
size_t datalen;
/*
* Here, mutex is required to serialize the calls to del_wk work between
* user/kernel space which happens when devcd is added with device_add()
* and that sends uevent to user space. User space reads the uevents,
* and calls to devcd_data_write() which try to modify the work which is
* not even initialized/queued from devcoredump.
*
*
*
* cpu0(X) cpu1(Y)
*
* dev_coredump() uevent sent to user space
* device_add() ======================> user space process Y reads the
* uevents writes to devcd fd
* which results into writes to
*
* devcd_data_write()
* mod_delayed_work()
* try_to_grab_pending()
* del_timer()
* debug_assert_init()
* INIT_DELAYED_WORK()
* schedule_delayed_work()
*
*
* Also, mutex alone would not be enough to avoid scheduling of
* del_wk work after it get flush from a call to devcd_free()
* mentioned as below.
*
* disabled_store()
* devcd_free()
* mutex_lock() devcd_data_write()
* flush_delayed_work()
* mutex_unlock()
* mutex_lock()
* mod_delayed_work()
* mutex_unlock()
* So, delete_work flag is required.
*/
struct mutex mutex;
bool delete_work;
struct module *owner;
ssize_t (*read)(char *buffer, loff_t offset, size_t count,
void *data, size_t datalen);
void (*free)(void *data);
struct delayed_work del_wk;
struct device *failing_dev;
};
static struct devcd_entry *dev_to_devcd(struct device *dev)
{
return container_of(dev, struct devcd_entry, devcd_dev);
}
static void devcd_dev_release(struct device *dev)
{
struct devcd_entry *devcd = dev_to_devcd(dev);
devcd->free(devcd->data);
module_put(devcd->owner);
/*
* this seems racy, but I don't see a notifier or such on
* a struct device to know when it goes away?
*/
if (devcd->failing_dev->kobj.sd)
sysfs_delete_link(&devcd->failing_dev->kobj, &dev->kobj,
"devcoredump");
put_device(devcd->failing_dev);
kfree(devcd);
}
static void devcd_del(struct work_struct *wk)
{
struct devcd_entry *devcd;
devcd = container_of(wk, struct devcd_entry, del_wk.work);
device_del(&devcd->devcd_dev);
put_device(&devcd->devcd_dev);
}
static ssize_t devcd_data_read(struct file *filp, struct kobject *kobj,
struct bin_attribute *bin_attr,
char *buffer, loff_t offset, size_t count)
{
struct device *dev = kobj_to_dev(kobj);
struct devcd_entry *devcd = dev_to_devcd(dev);
return devcd->read(buffer, offset, count, devcd->data, devcd->datalen);
}
static ssize_t devcd_data_write(struct file *filp, struct kobject *kobj,
struct bin_attribute *bin_attr,
char *buffer, loff_t offset, size_t count)
{
struct device *dev = kobj_to_dev(kobj);
struct devcd_entry *devcd = dev_to_devcd(dev);
mutex_lock(&devcd->mutex);
if (!devcd->delete_work) {
devcd->delete_work = true;
mod_delayed_work(system_wq, &devcd->del_wk, 0);
}
mutex_unlock(&devcd->mutex);
return count;
}
static struct bin_attribute devcd_attr_data = {
.attr = { .name = "data", .mode = S_IRUSR | S_IWUSR, },
.size = 0,
.read = devcd_data_read,
.write = devcd_data_write,
};
static struct bin_attribute *devcd_dev_bin_attrs[] = {
&devcd_attr_data, NULL,
};
static const struct attribute_group devcd_dev_group = {
.bin_attrs = devcd_dev_bin_attrs,
};
static const struct attribute_group *devcd_dev_groups[] = {
&devcd_dev_group, NULL,
};
static int devcd_free(struct device *dev, void *data)
{
struct devcd_entry *devcd = dev_to_devcd(dev);
mutex_lock(&devcd->mutex);
if (!devcd->delete_work)
devcd->delete_work = true;
flush_delayed_work(&devcd->del_wk);
mutex_unlock(&devcd->mutex);
return 0;
}
static ssize_t disabled_show(const struct class *class, const struct class_attribute *attr,
char *buf)
{
return sysfs_emit(buf, "%d\n", devcd_disabled);
}
/*
*
* disabled_store() worker()
* class_for_each_device(&devcd_class,
* NULL, NULL, devcd_free)
* ...
* ...
* while ((dev = class_dev_iter_next(&iter))
* devcd_del()
* device_del()
* put_device() <- last reference
* error = fn(dev, data) devcd_dev_release()
* devcd_free(dev, data) kfree(devcd)
* mutex_lock(&devcd->mutex);
*
*
* In the above diagram, It looks like disabled_store() would be racing with parallely
* running devcd_del() and result in memory abort while acquiring devcd->mutex which
* is called after kfree of devcd memory after dropping its last reference with
* put_device(). However, this will not happens as fn(dev, data) runs
* with its own reference to device via klist_node so it is not its last reference.
* so, above situation would not occur.
*/
static ssize_t disabled_store(const struct class *class, const struct class_attribute *attr,
const char *buf, size_t count)
{
long tmp = simple_strtol(buf, NULL, 10);
/*
* This essentially makes the attribute write-once, since you can't
* go back to not having it disabled. This is intentional, it serves
* as a system lockdown feature.
*/
if (tmp != 1)
return -EINVAL;
devcd_disabled = true;
class_for_each_device(&devcd_class, NULL, NULL, devcd_free);
return count;
}
static CLASS_ATTR_RW(disabled);
static struct attribute *devcd_class_attrs[] = {
&class_attr_disabled.attr,
NULL,
};
ATTRIBUTE_GROUPS(devcd_class);
static struct class devcd_class = {
.name = "devcoredump",
.dev_release = devcd_dev_release,
.dev_groups = devcd_dev_groups,
.class_groups = devcd_class_groups,
};
static ssize_t devcd_readv(char *buffer, loff_t offset, size_t count,
void *data, size_t datalen)
{
return memory_read_from_buffer(buffer, count, &offset, data, datalen);
}
static void devcd_freev(void *data)
{
vfree(data);
}
/**
* dev_coredumpv - create device coredump with vmalloc data
* @dev: the struct device for the crashed device
* @data: vmalloc data containing the device coredump
* @datalen: length of the data
* @gfp: allocation flags
*
* This function takes ownership of the vmalloc'ed data and will free
* it when it is no longer used. See dev_coredumpm() for more information.
*/
void dev_coredumpv(struct device *dev, void *data, size_t datalen,
gfp_t gfp)
{
dev_coredumpm(dev, NULL, data, datalen, gfp, devcd_readv, devcd_freev);
}
EXPORT_SYMBOL_GPL(dev_coredumpv);
static int devcd_match_failing(struct device *dev, const void *failing)
{
struct devcd_entry *devcd = dev_to_devcd(dev);
return devcd->failing_dev == failing;
}
/**
* devcd_free_sgtable - free all the memory of the given scatterlist table
* (i.e. both pages and scatterlist instances)
* NOTE: if two tables allocated with devcd_alloc_sgtable and then chained
* using the sg_chain function then that function should be called only once
* on the chained table
* @data: pointer to sg_table to free
*/
static void devcd_free_sgtable(void *data)
{
_devcd_free_sgtable(data);
}
/**
* devcd_read_from_sgtable - copy data from sg_table to a given buffer
* and return the number of bytes read
* @buffer: the buffer to copy the data to it
* @buf_len: the length of the buffer
* @data: the scatterlist table to copy from
* @offset: start copy from @offset@ bytes from the head of the data
* in the given scatterlist
* @data_len: the length of the data in the sg_table
*/
static ssize_t devcd_read_from_sgtable(char *buffer, loff_t offset,
size_t buf_len, void *data,
size_t data_len)
{
struct scatterlist *table = data;
if (offset > data_len)
return -EINVAL;
if (offset + buf_len > data_len)
buf_len = data_len - offset;
return sg_pcopy_to_buffer(table, sg_nents(table), buffer, buf_len,
offset);
}
/**
* dev_coredumpm - create device coredump with read/free methods
* @dev: the struct device for the crashed device
* @owner: the module that contains the read/free functions, use %THIS_MODULE
* @data: data cookie for the @read/@free functions
* @datalen: length of the data
* @gfp: allocation flags
* @read: function to read from the given buffer
* @free: function to free the given buffer
*
* Creates a new device coredump for the given device. If a previous one hasn't
* been read yet, the new coredump is discarded. The data lifetime is determined
* by the device coredump framework and when it is no longer needed the @free
* function will be called to free the data.
*/
void dev_coredumpm(struct device *dev, struct module *owner,
void *data, size_t datalen, gfp_t gfp,
ssize_t (*read)(char *buffer, loff_t offset, size_t count,
void *data, size_t datalen),
void (*free)(void *data))
{
static atomic_t devcd_count = ATOMIC_INIT(0);
struct devcd_entry *devcd;
struct device *existing;
if (devcd_disabled)
goto free;
existing = class_find_device(&devcd_class, NULL, dev,
devcd_match_failing);
if (existing) {
put_device(existing);
goto free;
}
if (!try_module_get(owner))
goto free;
devcd = kzalloc(sizeof(*devcd), gfp);
if (!devcd)
goto put_module;
devcd->owner = owner;
devcd->data = data;
devcd->datalen = datalen;
devcd->read = read;
devcd->free = free;
devcd->failing_dev = get_device(dev);
devcd->delete_work = false;
mutex_init(&devcd->mutex);
device_initialize(&devcd->devcd_dev);
dev_set_name(&devcd->devcd_dev, "devcd%d",
atomic_inc_return(&devcd_count));
devcd->devcd_dev.class = &devcd_class;
mutex_lock(&devcd->mutex);
if (device_add(&devcd->devcd_dev))
goto put_device;
/*
* These should normally not fail, but there is no problem
* continuing without the links, so just warn instead of
* failing.
*/
if (sysfs_create_link(&devcd->devcd_dev.kobj, &dev->kobj,
"failing_device") ||
sysfs_create_link(&dev->kobj, &devcd->devcd_dev.kobj,
"devcoredump"))
dev_warn(dev, "devcoredump create_link failed\n");
INIT_DELAYED_WORK(&devcd->del_wk, devcd_del);
schedule_delayed_work(&devcd->del_wk, DEVCD_TIMEOUT);
mutex_unlock(&devcd->mutex);
return;
put_device:
put_device(&devcd->devcd_dev);
mutex_unlock(&devcd->mutex);
put_module:
module_put(owner);
free:
free(data);
}
EXPORT_SYMBOL_GPL(dev_coredumpm);
/**
* dev_coredumpsg - create device coredump that uses scatterlist as data
* parameter
* @dev: the struct device for the crashed device
* @table: the dump data
* @datalen: length of the data
* @gfp: allocation flags
*
* Creates a new device coredump for the given device. If a previous one hasn't
* been read yet, the new coredump is discarded. The data lifetime is determined
* by the device coredump framework and when it is no longer needed
* it will free the data.
*/
void dev_coredumpsg(struct device *dev, struct scatterlist *table,
size_t datalen, gfp_t gfp)
{
dev_coredumpm(dev, NULL, table, datalen, gfp, devcd_read_from_sgtable,
devcd_free_sgtable);
}
EXPORT_SYMBOL_GPL(dev_coredumpsg);
static int __init devcoredump_init(void)
{
return class_register(&devcd_class);
}
__initcall(devcoredump_init);
static void __exit devcoredump_exit(void)
{
class_for_each_device(&devcd_class, NULL, NULL, devcd_free);
class_unregister(&devcd_class);
}
__exitcall(devcoredump_exit);