linux/fs/proc/kcore.c
Laura Abbott 3955333df9 proc/kcore: don't bounds check against address 0
The existing kcore code checks for bad addresses against __va(0) with
the assumption that this is the lowest address on the system.  This may
not hold true on some systems (e.g.  arm64) and produce overflows and
crashes.  Switch to using other functions to validate the address range.

It's currently only seen on arm64 and it's not clear if anyone wants to
use that particular combination on a stable release.  So this is not
urgent for stable.

Link: http://lkml.kernel.org/r/20180501201143.15121-1-labbott@redhat.com
Signed-off-by: Laura Abbott <labbott@redhat.com>
Tested-by: Dave Anderson <anderson@redhat.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: Alexey Dobriyan <adobriyan@gmail.com>a
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2018-05-11 17:28:45 -07:00

664 lines
16 KiB
C

// SPDX-License-Identifier: GPL-2.0
/*
* fs/proc/kcore.c kernel ELF core dumper
*
* Modelled on fs/exec.c:aout_core_dump()
* Jeremy Fitzhardinge <jeremy@sw.oz.au>
* ELF version written by David Howells <David.Howells@nexor.co.uk>
* Modified and incorporated into 2.3.x by Tigran Aivazian <tigran@veritas.com>
* Support to dump vmalloc'd areas (ELF only), Tigran Aivazian <tigran@veritas.com>
* Safe accesses to vmalloc/direct-mapped discontiguous areas, Kanoj Sarcar <kanoj@sgi.com>
*/
#include <linux/mm.h>
#include <linux/proc_fs.h>
#include <linux/kcore.h>
#include <linux/user.h>
#include <linux/capability.h>
#include <linux/elf.h>
#include <linux/elfcore.h>
#include <linux/notifier.h>
#include <linux/vmalloc.h>
#include <linux/highmem.h>
#include <linux/printk.h>
#include <linux/bootmem.h>
#include <linux/init.h>
#include <linux/slab.h>
#include <linux/uaccess.h>
#include <asm/io.h>
#include <linux/list.h>
#include <linux/ioport.h>
#include <linux/memory.h>
#include <linux/sched/task.h>
#include <asm/sections.h>
#include "internal.h"
#define CORE_STR "CORE"
#ifndef ELF_CORE_EFLAGS
#define ELF_CORE_EFLAGS 0
#endif
static struct proc_dir_entry *proc_root_kcore;
#ifndef kc_vaddr_to_offset
#define kc_vaddr_to_offset(v) ((v) - PAGE_OFFSET)
#endif
#ifndef kc_offset_to_vaddr
#define kc_offset_to_vaddr(o) ((o) + PAGE_OFFSET)
#endif
/* An ELF note in memory */
struct memelfnote
{
const char *name;
int type;
unsigned int datasz;
void *data;
};
static LIST_HEAD(kclist_head);
static DEFINE_RWLOCK(kclist_lock);
static int kcore_need_update = 1;
void
kclist_add(struct kcore_list *new, void *addr, size_t size, int type)
{
new->addr = (unsigned long)addr;
new->size = size;
new->type = type;
write_lock(&kclist_lock);
list_add_tail(&new->list, &kclist_head);
write_unlock(&kclist_lock);
}
static size_t get_kcore_size(int *nphdr, size_t *elf_buflen)
{
size_t try, size;
struct kcore_list *m;
*nphdr = 1; /* PT_NOTE */
size = 0;
list_for_each_entry(m, &kclist_head, list) {
try = kc_vaddr_to_offset((size_t)m->addr + m->size);
if (try > size)
size = try;
*nphdr = *nphdr + 1;
}
*elf_buflen = sizeof(struct elfhdr) +
(*nphdr + 2)*sizeof(struct elf_phdr) +
3 * ((sizeof(struct elf_note)) +
roundup(sizeof(CORE_STR), 4)) +
roundup(sizeof(struct elf_prstatus), 4) +
roundup(sizeof(struct elf_prpsinfo), 4) +
roundup(arch_task_struct_size, 4);
*elf_buflen = PAGE_ALIGN(*elf_buflen);
return size + *elf_buflen;
}
static void free_kclist_ents(struct list_head *head)
{
struct kcore_list *tmp, *pos;
list_for_each_entry_safe(pos, tmp, head, list) {
list_del(&pos->list);
kfree(pos);
}
}
/*
* Replace all KCORE_RAM/KCORE_VMEMMAP information with passed list.
*/
static void __kcore_update_ram(struct list_head *list)
{
int nphdr;
size_t size;
struct kcore_list *tmp, *pos;
LIST_HEAD(garbage);
write_lock(&kclist_lock);
if (kcore_need_update) {
list_for_each_entry_safe(pos, tmp, &kclist_head, list) {
if (pos->type == KCORE_RAM
|| pos->type == KCORE_VMEMMAP)
list_move(&pos->list, &garbage);
}
list_splice_tail(list, &kclist_head);
} else
list_splice(list, &garbage);
kcore_need_update = 0;
proc_root_kcore->size = get_kcore_size(&nphdr, &size);
write_unlock(&kclist_lock);
free_kclist_ents(&garbage);
}
#ifdef CONFIG_HIGHMEM
/*
* If no highmem, we can assume [0...max_low_pfn) continuous range of memory
* because memory hole is not as big as !HIGHMEM case.
* (HIGHMEM is special because part of memory is _invisible_ from the kernel.)
*/
static int kcore_update_ram(void)
{
LIST_HEAD(head);
struct kcore_list *ent;
int ret = 0;
ent = kmalloc(sizeof(*ent), GFP_KERNEL);
if (!ent)
return -ENOMEM;
ent->addr = (unsigned long)__va(0);
ent->size = max_low_pfn << PAGE_SHIFT;
ent->type = KCORE_RAM;
list_add(&ent->list, &head);
__kcore_update_ram(&head);
return ret;
}
#else /* !CONFIG_HIGHMEM */
#ifdef CONFIG_SPARSEMEM_VMEMMAP
/* calculate vmemmap's address from given system ram pfn and register it */
static int
get_sparsemem_vmemmap_info(struct kcore_list *ent, struct list_head *head)
{
unsigned long pfn = __pa(ent->addr) >> PAGE_SHIFT;
unsigned long nr_pages = ent->size >> PAGE_SHIFT;
unsigned long start, end;
struct kcore_list *vmm, *tmp;
start = ((unsigned long)pfn_to_page(pfn)) & PAGE_MASK;
end = ((unsigned long)pfn_to_page(pfn + nr_pages)) - 1;
end = PAGE_ALIGN(end);
/* overlap check (because we have to align page */
list_for_each_entry(tmp, head, list) {
if (tmp->type != KCORE_VMEMMAP)
continue;
if (start < tmp->addr + tmp->size)
if (end > tmp->addr)
end = tmp->addr;
}
if (start < end) {
vmm = kmalloc(sizeof(*vmm), GFP_KERNEL);
if (!vmm)
return 0;
vmm->addr = start;
vmm->size = end - start;
vmm->type = KCORE_VMEMMAP;
list_add_tail(&vmm->list, head);
}
return 1;
}
#else
static int
get_sparsemem_vmemmap_info(struct kcore_list *ent, struct list_head *head)
{
return 1;
}
#endif
static int
kclist_add_private(unsigned long pfn, unsigned long nr_pages, void *arg)
{
struct list_head *head = (struct list_head *)arg;
struct kcore_list *ent;
struct page *p;
if (!pfn_valid(pfn))
return 1;
p = pfn_to_page(pfn);
if (!memmap_valid_within(pfn, p, page_zone(p)))
return 1;
ent = kmalloc(sizeof(*ent), GFP_KERNEL);
if (!ent)
return -ENOMEM;
ent->addr = (unsigned long)page_to_virt(p);
ent->size = nr_pages << PAGE_SHIFT;
if (!virt_addr_valid(ent->addr))
goto free_out;
/* cut not-mapped area. ....from ppc-32 code. */
if (ULONG_MAX - ent->addr < ent->size)
ent->size = ULONG_MAX - ent->addr;
/*
* We've already checked virt_addr_valid so we know this address
* is a valid pointer, therefore we can check against it to determine
* if we need to trim
*/
if (VMALLOC_START > ent->addr) {
if (VMALLOC_START - ent->addr < ent->size)
ent->size = VMALLOC_START - ent->addr;
}
ent->type = KCORE_RAM;
list_add_tail(&ent->list, head);
if (!get_sparsemem_vmemmap_info(ent, head)) {
list_del(&ent->list);
goto free_out;
}
return 0;
free_out:
kfree(ent);
return 1;
}
static int kcore_update_ram(void)
{
int nid, ret;
unsigned long end_pfn;
LIST_HEAD(head);
/* Not inialized....update now */
/* find out "max pfn" */
end_pfn = 0;
for_each_node_state(nid, N_MEMORY) {
unsigned long node_end;
node_end = node_end_pfn(nid);
if (end_pfn < node_end)
end_pfn = node_end;
}
/* scan 0 to max_pfn */
ret = walk_system_ram_range(0, end_pfn, &head, kclist_add_private);
if (ret) {
free_kclist_ents(&head);
return -ENOMEM;
}
__kcore_update_ram(&head);
return ret;
}
#endif /* CONFIG_HIGHMEM */
/*****************************************************************************/
/*
* determine size of ELF note
*/
static int notesize(struct memelfnote *en)
{
int sz;
sz = sizeof(struct elf_note);
sz += roundup((strlen(en->name) + 1), 4);
sz += roundup(en->datasz, 4);
return sz;
} /* end notesize() */
/*****************************************************************************/
/*
* store a note in the header buffer
*/
static char *storenote(struct memelfnote *men, char *bufp)
{
struct elf_note en;
#define DUMP_WRITE(addr,nr) do { memcpy(bufp,addr,nr); bufp += nr; } while(0)
en.n_namesz = strlen(men->name) + 1;
en.n_descsz = men->datasz;
en.n_type = men->type;
DUMP_WRITE(&en, sizeof(en));
DUMP_WRITE(men->name, en.n_namesz);
/* XXX - cast from long long to long to avoid need for libgcc.a */
bufp = (char*) roundup((unsigned long)bufp,4);
DUMP_WRITE(men->data, men->datasz);
bufp = (char*) roundup((unsigned long)bufp,4);
#undef DUMP_WRITE
return bufp;
} /* end storenote() */
/*
* store an ELF coredump header in the supplied buffer
* nphdr is the number of elf_phdr to insert
*/
static void elf_kcore_store_hdr(char *bufp, int nphdr, int dataoff)
{
struct elf_prstatus prstatus; /* NT_PRSTATUS */
struct elf_prpsinfo prpsinfo; /* NT_PRPSINFO */
struct elf_phdr *nhdr, *phdr;
struct elfhdr *elf;
struct memelfnote notes[3];
off_t offset = 0;
struct kcore_list *m;
/* setup ELF header */
elf = (struct elfhdr *) bufp;
bufp += sizeof(struct elfhdr);
offset += sizeof(struct elfhdr);
memcpy(elf->e_ident, ELFMAG, SELFMAG);
elf->e_ident[EI_CLASS] = ELF_CLASS;
elf->e_ident[EI_DATA] = ELF_DATA;
elf->e_ident[EI_VERSION]= EV_CURRENT;
elf->e_ident[EI_OSABI] = ELF_OSABI;
memset(elf->e_ident+EI_PAD, 0, EI_NIDENT-EI_PAD);
elf->e_type = ET_CORE;
elf->e_machine = ELF_ARCH;
elf->e_version = EV_CURRENT;
elf->e_entry = 0;
elf->e_phoff = sizeof(struct elfhdr);
elf->e_shoff = 0;
elf->e_flags = ELF_CORE_EFLAGS;
elf->e_ehsize = sizeof(struct elfhdr);
elf->e_phentsize= sizeof(struct elf_phdr);
elf->e_phnum = nphdr;
elf->e_shentsize= 0;
elf->e_shnum = 0;
elf->e_shstrndx = 0;
/* setup ELF PT_NOTE program header */
nhdr = (struct elf_phdr *) bufp;
bufp += sizeof(struct elf_phdr);
offset += sizeof(struct elf_phdr);
nhdr->p_type = PT_NOTE;
nhdr->p_offset = 0;
nhdr->p_vaddr = 0;
nhdr->p_paddr = 0;
nhdr->p_filesz = 0;
nhdr->p_memsz = 0;
nhdr->p_flags = 0;
nhdr->p_align = 0;
/* setup ELF PT_LOAD program header for every area */
list_for_each_entry(m, &kclist_head, list) {
phdr = (struct elf_phdr *) bufp;
bufp += sizeof(struct elf_phdr);
offset += sizeof(struct elf_phdr);
phdr->p_type = PT_LOAD;
phdr->p_flags = PF_R|PF_W|PF_X;
phdr->p_offset = kc_vaddr_to_offset(m->addr) + dataoff;
phdr->p_vaddr = (size_t)m->addr;
if (m->type == KCORE_RAM || m->type == KCORE_TEXT)
phdr->p_paddr = __pa(m->addr);
else
phdr->p_paddr = (elf_addr_t)-1;
phdr->p_filesz = phdr->p_memsz = m->size;
phdr->p_align = PAGE_SIZE;
}
/*
* Set up the notes in similar form to SVR4 core dumps made
* with info from their /proc.
*/
nhdr->p_offset = offset;
/* set up the process status */
notes[0].name = CORE_STR;
notes[0].type = NT_PRSTATUS;
notes[0].datasz = sizeof(struct elf_prstatus);
notes[0].data = &prstatus;
memset(&prstatus, 0, sizeof(struct elf_prstatus));
nhdr->p_filesz = notesize(&notes[0]);
bufp = storenote(&notes[0], bufp);
/* set up the process info */
notes[1].name = CORE_STR;
notes[1].type = NT_PRPSINFO;
notes[1].datasz = sizeof(struct elf_prpsinfo);
notes[1].data = &prpsinfo;
memset(&prpsinfo, 0, sizeof(struct elf_prpsinfo));
prpsinfo.pr_state = 0;
prpsinfo.pr_sname = 'R';
prpsinfo.pr_zomb = 0;
strcpy(prpsinfo.pr_fname, "vmlinux");
strlcpy(prpsinfo.pr_psargs, saved_command_line, sizeof(prpsinfo.pr_psargs));
nhdr->p_filesz += notesize(&notes[1]);
bufp = storenote(&notes[1], bufp);
/* set up the task structure */
notes[2].name = CORE_STR;
notes[2].type = NT_TASKSTRUCT;
notes[2].datasz = arch_task_struct_size;
notes[2].data = current;
nhdr->p_filesz += notesize(&notes[2]);
bufp = storenote(&notes[2], bufp);
} /* end elf_kcore_store_hdr() */
/*****************************************************************************/
/*
* read from the ELF header and then kernel memory
*/
static ssize_t
read_kcore(struct file *file, char __user *buffer, size_t buflen, loff_t *fpos)
{
char *buf = file->private_data;
ssize_t acc = 0;
size_t size, tsz;
size_t elf_buflen;
int nphdr;
unsigned long start;
read_lock(&kclist_lock);
size = get_kcore_size(&nphdr, &elf_buflen);
if (buflen == 0 || *fpos >= size) {
read_unlock(&kclist_lock);
return 0;
}
/* trim buflen to not go beyond EOF */
if (buflen > size - *fpos)
buflen = size - *fpos;
/* construct an ELF core header if we'll need some of it */
if (*fpos < elf_buflen) {
char * elf_buf;
tsz = elf_buflen - *fpos;
if (buflen < tsz)
tsz = buflen;
elf_buf = kzalloc(elf_buflen, GFP_ATOMIC);
if (!elf_buf) {
read_unlock(&kclist_lock);
return -ENOMEM;
}
elf_kcore_store_hdr(elf_buf, nphdr, elf_buflen);
read_unlock(&kclist_lock);
if (copy_to_user(buffer, elf_buf + *fpos, tsz)) {
kfree(elf_buf);
return -EFAULT;
}
kfree(elf_buf);
buflen -= tsz;
*fpos += tsz;
buffer += tsz;
acc += tsz;
/* leave now if filled buffer already */
if (buflen == 0)
return acc;
} else
read_unlock(&kclist_lock);
/*
* Check to see if our file offset matches with any of
* the addresses in the elf_phdr on our list.
*/
start = kc_offset_to_vaddr(*fpos - elf_buflen);
if ((tsz = (PAGE_SIZE - (start & ~PAGE_MASK))) > buflen)
tsz = buflen;
while (buflen) {
struct kcore_list *m;
read_lock(&kclist_lock);
list_for_each_entry(m, &kclist_head, list) {
if (start >= m->addr && start < (m->addr+m->size))
break;
}
read_unlock(&kclist_lock);
if (&m->list == &kclist_head) {
if (clear_user(buffer, tsz))
return -EFAULT;
} else if (m->type == KCORE_VMALLOC) {
vread(buf, (char *)start, tsz);
/* we have to zero-fill user buffer even if no read */
if (copy_to_user(buffer, buf, tsz))
return -EFAULT;
} else if (m->type == KCORE_USER) {
/* User page is handled prior to normal kernel page: */
if (copy_to_user(buffer, (char *)start, tsz))
return -EFAULT;
} else {
if (kern_addr_valid(start)) {
/*
* Using bounce buffer to bypass the
* hardened user copy kernel text checks.
*/
if (probe_kernel_read(buf, (void *) start, tsz)) {
if (clear_user(buffer, tsz))
return -EFAULT;
} else {
if (copy_to_user(buffer, buf, tsz))
return -EFAULT;
}
} else {
if (clear_user(buffer, tsz))
return -EFAULT;
}
}
buflen -= tsz;
*fpos += tsz;
buffer += tsz;
acc += tsz;
start += tsz;
tsz = (buflen > PAGE_SIZE ? PAGE_SIZE : buflen);
}
return acc;
}
static int open_kcore(struct inode *inode, struct file *filp)
{
if (!capable(CAP_SYS_RAWIO))
return -EPERM;
filp->private_data = kmalloc(PAGE_SIZE, GFP_KERNEL);
if (!filp->private_data)
return -ENOMEM;
if (kcore_need_update)
kcore_update_ram();
if (i_size_read(inode) != proc_root_kcore->size) {
inode_lock(inode);
i_size_write(inode, proc_root_kcore->size);
inode_unlock(inode);
}
return 0;
}
static int release_kcore(struct inode *inode, struct file *file)
{
kfree(file->private_data);
return 0;
}
static const struct file_operations proc_kcore_operations = {
.read = read_kcore,
.open = open_kcore,
.release = release_kcore,
.llseek = default_llseek,
};
/* just remember that we have to update kcore */
static int __meminit kcore_callback(struct notifier_block *self,
unsigned long action, void *arg)
{
switch (action) {
case MEM_ONLINE:
case MEM_OFFLINE:
write_lock(&kclist_lock);
kcore_need_update = 1;
write_unlock(&kclist_lock);
}
return NOTIFY_OK;
}
static struct notifier_block kcore_callback_nb __meminitdata = {
.notifier_call = kcore_callback,
.priority = 0,
};
static struct kcore_list kcore_vmalloc;
#ifdef CONFIG_ARCH_PROC_KCORE_TEXT
static struct kcore_list kcore_text;
/*
* If defined, special segment is used for mapping kernel text instead of
* direct-map area. We need to create special TEXT section.
*/
static void __init proc_kcore_text_init(void)
{
kclist_add(&kcore_text, _text, _end - _text, KCORE_TEXT);
}
#else
static void __init proc_kcore_text_init(void)
{
}
#endif
#if defined(CONFIG_MODULES) && defined(MODULES_VADDR)
/*
* MODULES_VADDR has no intersection with VMALLOC_ADDR.
*/
struct kcore_list kcore_modules;
static void __init add_modules_range(void)
{
if (MODULES_VADDR != VMALLOC_START && MODULES_END != VMALLOC_END) {
kclist_add(&kcore_modules, (void *)MODULES_VADDR,
MODULES_END - MODULES_VADDR, KCORE_VMALLOC);
}
}
#else
static void __init add_modules_range(void)
{
}
#endif
static int __init proc_kcore_init(void)
{
proc_root_kcore = proc_create("kcore", S_IRUSR, NULL,
&proc_kcore_operations);
if (!proc_root_kcore) {
pr_err("couldn't create /proc/kcore\n");
return 0; /* Always returns 0. */
}
/* Store text area if it's special */
proc_kcore_text_init();
/* Store vmalloc area */
kclist_add(&kcore_vmalloc, (void *)VMALLOC_START,
VMALLOC_END - VMALLOC_START, KCORE_VMALLOC);
add_modules_range();
/* Store direct-map area from physical memory map */
kcore_update_ram();
register_hotmemory_notifier(&kcore_callback_nb);
return 0;
}
fs_initcall(proc_kcore_init);