From: Dan Aloni <[email protected]>
Subject: 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
Issue originating in 2aa362c49 ("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.
[[email protected]: avoid abusing E2BIG, remove a couple of
not-really-needed local variables]
[[email protected]: fix sparse warning]
Signed-off-by: Dan Aloni <[email protected]>
Cc: Al Viro <[email protected]>
Cc: Denys Vlasenko <[email protected]>
Reported-by: Martin MOKREJS <[email protected]>
Tested-by: Martin MOKREJS <[email protected]>
Cc: <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
---
fs/binfmt_elf.c | 30 ++++++++++++++++++------------
1 file changed, 18 insertions(+), 12 deletions(-)
diff -puN
fs/binfmt_elf.c~fs-binfmt_elfc-prevent-a-coredump-with-a-large-vm_map_count-from-oopsing
fs/binfmt_elf.c
---
a/fs/binfmt_elf.c~fs-binfmt_elfc-prevent-a-coredump-with-a-large-vm_map_count-from-oopsing
+++ a/fs/binfmt_elf.c
@@ -1413,7 +1413,7 @@ static void fill_siginfo_note(struct mem
* 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 memel
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 memel
size = name_curpos - (char *)data;
fill_note(note, "CORE", NT_FILE, size, data);
- err: ;
+ return 0;
}
#ifdef CORE_DUMP_USE_REGSET
@@ -1686,8 +1686,8 @@ static int fill_note_info(struct elfhdr
fill_auxv_note(&info->auxv, current->mm);
info->size += notesize(&info->auxv);
- fill_files_note(&info->files);
- info->size += notesize(&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_no
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 s
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
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_no
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
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;
_
--
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