[ 36/56] coredump: prevent double-free on an error path in core dumper

From: Greg Kroah-Hartman
Date: Thu Oct 04 2012 - 17:18:25 EST


3.6-stable review patch. If anyone has any objections, please let me know.

------------------

From: Denys Vlasenko <vda.linux@xxxxxxxxxxxxxx>

commit f34f9d186df35e5c39163444c43b4fc6255e39c5 upstream.

In !CORE_DUMP_USE_REGSET case, if elf_note_info_init fails to allocate
memory for info->fields, it frees already allocated stuff and returns
error to its caller, fill_note_info. Which in turn returns error to its
caller, elf_core_dump. Which jumps to cleanup label and calls
free_note_info, which will happily try to free all info->fields again.
BOOM.

This is the fix.

Signed-off-by: Oleg Nesterov <oleg@xxxxxxxxxx>
Signed-off-by: Denys Vlasenko <vda.linux@xxxxxxxxxxxxxx>
Cc: Venu Byravarasu <vbyravarasu@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
fs/binfmt_elf.c | 19 ++++---------------
1 file changed, 4 insertions(+), 15 deletions(-)

--- a/fs/binfmt_elf.c
+++ b/fs/binfmt_elf.c
@@ -1696,30 +1696,19 @@ static int elf_note_info_init(struct elf
return 0;
info->psinfo = kmalloc(sizeof(*info->psinfo), GFP_KERNEL);
if (!info->psinfo)
- goto notes_free;
+ return 0;
info->prstatus = kmalloc(sizeof(*info->prstatus), GFP_KERNEL);
if (!info->prstatus)
- goto psinfo_free;
+ return 0;
info->fpu = kmalloc(sizeof(*info->fpu), GFP_KERNEL);
if (!info->fpu)
- goto prstatus_free;
+ return 0;
#ifdef ELF_CORE_COPY_XFPREGS
info->xfpu = kmalloc(sizeof(*info->xfpu), GFP_KERNEL);
if (!info->xfpu)
- goto fpu_free;
+ return 0;
#endif
return 1;
-#ifdef ELF_CORE_COPY_XFPREGS
- fpu_free:
- kfree(info->fpu);
-#endif
- prstatus_free:
- kfree(info->prstatus);
- psinfo_free:
- kfree(info->psinfo);
- notes_free:
- kfree(info->notes);
- return 0;
}

static int fill_note_info(struct elfhdr *elf, int phdrs,


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