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Date: Sat, 31 Aug 2013 09:20:42 +0300
From: Dan Aloni <alonid@...atoscale.com>
To: akpm@...ux-foundation.org
Cc: linux-kernel@...r.kernel.org, gregkh@...uxfoundation.org,
mmokrejs@...il.com, Al Viro <viro@...iv.linux.org.uk>,
Denys Vlasenko <vda.linux@...glemail.com>,
Linus Torvalds <torvalds@...ux-foundation.org>
Subject: [PATCH linux-next] 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 bug described here:
https://lkml.org/lkml/2013/8/30/50
Issue originating in 2aa362c49 (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.
Cc'ed original signers.
Cc'ed Al Viro because it is trivially relies on his linux-next
tree changes.
Signed-off-by: Dan Aloni <alonid@...atoscale.com>
Cc: Al Viro <viro@...iv.linux.org.uk>
Cc: Denys Vlasenko <vda.linux@...glemail.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
---
fs/binfmt_elf.c | 33 +++++++++++++++++++++------------
1 file changed, 21 insertions(+), 12 deletions(-)
diff --git a/fs/binfmt_elf.c b/fs/binfmt_elf.c
index dc82279..e1a323a 100644
--- a/fs/binfmt_elf.c
+++ b/fs/binfmt_elf.c
@@ -1429,7 +1429,7 @@ 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;
@@ -1444,11 +1444,11 @@ 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 -E2BIG;
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;
@@ -1501,7 +1501,7 @@ 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
@@ -1623,6 +1623,7 @@ static int fill_note_info(struct elfhdr *elf, int phdrs,
struct elf_prpsinfo *psinfo;
struct core_thread *ct;
unsigned int i;
+ int ret;
info->size = 0;
info->thread = NULL;
@@ -1702,8 +1703,9 @@ 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);
- info->size += notesize(&info->files);
+ ret = fill_files_note(&info->files);
+ if (!ret)
+ info->size += notesize(&info->files);
return 1;
}
@@ -1735,7 +1737,7 @@ static int write_note_info(struct elf_note_info *info,
return 0;
if (first && !writenote(&info->auxv, cprm))
return 0;
- if (first && !writenote(&info->files, cprm))
+ if (first && info->files.data && !writenote(&info->files, cprm))
return 0;
for (i = 1; i < info->thread_notes; ++i)
@@ -1822,6 +1824,7 @@ 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;
@@ -1865,6 +1868,7 @@ static int fill_note_info(struct elfhdr *elf, int phdrs,
siginfo_t *siginfo, struct pt_regs *regs)
{
struct list_head *t;
+ int ret;
if (!elf_note_info_init(info))
return 0;
@@ -1912,9 +1916,13 @@ 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;
+ ret = fill_files_note(info->notes + info->numnote);
+ if (!ret) {
+ 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,
@@ -1976,8 +1984,9 @@ 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);
@@ -2059,7 +2068,7 @@ 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;
- struct elf_note_info info;
+ struct elf_note_info info = {0, };
struct elf_phdr *phdr4note = NULL;
struct elf_shdr *shdr4extnum = NULL;
Elf_Half e_phnum;
--
1.8.1.4
--
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