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fs/binfmt_elf.c: prevent a coredump with a large vm_map_count from Oopsing 

A high setting of max_map_count, and a process core-dumping with a large
enough vm_map_count could result in an NT_FILE note not being written,
and the kernel crashing immediately later because it has assumed
otherwise.

Reproduction of the oops-causing bug described here:

    https://lkml.org/lkml/2013/8/30/50

Rge ussue originated in commit 2aa362c49c ("coredump: extend core dump
note section to contain file names of mapped file") from Oct 4, 2012.

This patch make that section optional in that case.  fill_files_note()
should signify the error, and also let the info struct in
elf_core_dump() be zero-initialized so that we can check for the
optionally written note.

[akpm@linux-foundation.org: avoid abusing E2BIG, remove a couple of not-really-needed local variables]
[akpm@linux-foundation.org: fix sparse warning]
Signed-off-by: Dan Aloni <alonid@stratoscale.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Denys Vlasenko <vda.linux@googlemail.com>
Reported-by: Martin MOKREJS <mmokrejs@gmail.com>
Tested-by: Martin MOKREJS <mmokrejs@gmail.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Dan Aloni 2013-09-30 13:45:02 -07:00 committed by Linus Torvalds
parent 7393dc45f6
commit 7202365696
1 changed files with 18 additions and 12 deletions
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28
fs/binfmt_elf.c
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@ -1413,7 +1413,7 @@ static void fill_siginfo_note(struct memelfnote *note, user_siginfo_t *csigdata,
* long file_ofs
* followed by COUNT filenames in ASCII: "FILE1" NUL "FILE2" NUL...
*/
static void fill_files_note(struct memelfnote *note)
static int fill_files_note(struct memelfnote *note)
{
struct vm_area_struct *vma;
unsigned count, size, names_ofs, remaining, n;
@ -1428,11 +1428,11 @@ static void fill_files_note(struct memelfnote *note)
names_ofs = (2 + 3 * count) * sizeof(data[0]);
alloc:
if (size >= MAX_FILE_NOTE_SIZE) /* paranoia check */
goto err;
return -EINVAL;
size = round_up(size, PAGE_SIZE);
data = vmalloc(size);
if (!data)
goto err;
return -ENOMEM;
start_end_ofs = data + 2;
name_base = name_curpos = ((char *)data) + names_ofs;
@ -1485,7 +1485,7 @@ static void fill_files_note(struct memelfnote *note)
size = name_curpos - (char *)data;
fill_note(note, "CORE", NT_FILE, size, data);
err: ;
return 0;
}
#ifdef CORE_DUMP_USE_REGSET
@ -1686,7 +1686,7 @@ static int fill_note_info(struct elfhdr *elf, int phdrs,
fill_auxv_note(&info->auxv, current->mm);
info->size += notesize(&info->auxv);
fill_files_note(&info->files);
if (fill_files_note(&info->files) == 0)
info->size += notesize(&info->files);
return 1;
@ -1719,7 +1719,8 @@ static int write_note_info(struct elf_note_info *info,
return 0;
if (first && !writenote(&info->auxv, file, foffset))
return 0;
if (first && !writenote(&info->files, file, foffset))
if (first && info->files.data &&
!writenote(&info->files, file, foffset))
return 0;
for (i = 1; i < info->thread_notes; ++i)
@ -1806,6 +1807,7 @@ static int elf_dump_thread_status(long signr, struct elf_thread_status *t)
struct elf_note_info {
struct memelfnote *notes;
struct memelfnote *notes_files;
struct elf_prstatus *prstatus; /* NT_PRSTATUS */
struct elf_prpsinfo *psinfo; /* NT_PRPSINFO */
struct list_head thread_list;
@ -1896,9 +1898,12 @@ static int fill_note_info(struct elfhdr *elf, int phdrs,
fill_siginfo_note(info->notes + 2, &info->csigdata, siginfo);
fill_auxv_note(info->notes + 3, current->mm);
fill_files_note(info->notes + 4);
info->numnote = 4;
info->numnote = 5;
if (fill_files_note(info->notes + info->numnote) == 0) {
info->notes_files = info->notes + info->numnote;
info->numnote++;
}
/* Try to dump the FPU. */
info->prstatus->pr_fpvalid = elf_core_copy_task_fpregs(current, regs,
@ -1960,8 +1965,9 @@ static void free_note_info(struct elf_note_info *info)
kfree(list_entry(tmp, struct elf_thread_status, list));
}
/* Free data allocated by fill_files_note(): */
vfree(info->notes[4].data);
/* Free data possibly allocated by fill_files_note(): */
if (info->notes_files)
vfree(info->notes_files->data);
kfree(info->prstatus);
kfree(info->psinfo);
@ -2044,7 +2050,7 @@ static int elf_core_dump(struct coredump_params *cprm)
struct vm_area_struct *vma, *gate_vma;
struct elfhdr *elf = NULL;
loff_t offset = 0, dataoff, foffset;
struct elf_note_info info;
struct elf_note_info info = { };
struct elf_phdr *phdr4note = NULL;
struct elf_shdr *shdr4extnum = NULL;
Elf_Half e_phnum;