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| author | Eric Dumazet <edumazet@google.com> | 2014-04-19 10:15:07 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2014-04-19 13:23:31 -0700 |
| commit | 404ca80eb5c2727d78cd517d12108b040c522e12 (patch) | |
| tree | 0ff760410325ec53b260f16d844969965921c793 | |
| parent | 6d4596905b65bf4c63c1a008f50bf385fa49f19b (diff) | |
| download | linux-404ca80eb5c2727d78cd517d12108b040c522e12.tar.gz linux-404ca80eb5c2727d78cd517d12108b040c522e12.tar.bz2 linux-404ca80eb5c2727d78cd517d12108b040c522e12.zip | |
coredump: fix va_list corruption
A va_list needs to be copied in case it needs to be used twice.
Thanks to Hugh for debugging this issue, leading to various panics.
Tested:
lpq84:~# echo "|/foobar12345 %h %h %h %h %h %h %h %h %h %h %h %h %h %h %h %h %h %h %h %h" >/proc/sys/kernel/core_pattern
'produce_core' is simply : main() { *(int *)0 = 1;}
lpq84:~# ./produce_core
Segmentation fault (core dumped)
lpq84:~# dmesg | tail -1
[ 614.352947] Core dump to |/foobar12345 lpq84 lpq84 lpq84 lpq84 lpq84 lpq84 lpq84 lpq84 lpq84 lpq84 lpq84 lpq84 lpq84 lpq84 lpq84 lpq84 lpq84 lpq84 lpq84 (null) pipe failed
Notice the last argument was replaced by a NULL (we were lucky enough to
not crash, but do not try this on your production machine !)
After fix :
lpq83:~# echo "|/foobar12345 %h %h %h %h %h %h %h %h %h %h %h %h %h %h %h %h %h %h %h %h" >/proc/sys/kernel/core_pattern
lpq83:~# ./produce_core
Segmentation fault
lpq83:~# dmesg | tail -1
[ 740.800441] Core dump to |/foobar12345 lpq83 lpq83 lpq83 lpq83 lpq83 lpq83 lpq83 lpq83 lpq83 lpq83 lpq83 lpq83 lpq83 lpq83 lpq83 lpq83 lpq83 lpq83 lpq83 lpq83 pipe failed
Fixes: 5fe9d8ca21cc ("coredump: cn_vprintf() has no reason to call vsnprintf() twice")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Diagnosed-by: Hugh Dickins <hughd@google.com>
Acked-by: Oleg Nesterov <oleg@redhat.com>
Cc: Neil Horman <nhorman@tuxdriver.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: stable@vger.kernel.org # 3.11+
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
| -rw-r--r-- | fs/coredump.c | 7 |
1 files changed, 6 insertions, 1 deletions
diff --git a/fs/coredump.c b/fs/coredump.c index e3ad709a4232..0b2528fb640e 100644 --- a/fs/coredump.c +++ b/fs/coredump.c @@ -73,10 +73,15 @@ static int expand_corename(struct core_name *cn, int size) static int cn_vprintf(struct core_name *cn, const char *fmt, va_list arg) { int free, need; + va_list arg_copy; again: free = cn->size - cn->used; - need = vsnprintf(cn->corename + cn->used, free, fmt, arg); + + va_copy(arg_copy, arg); + need = vsnprintf(cn->corename + cn->used, free, fmt, arg_copy); + va_end(arg_copy); + if (need < free) { cn->used += need; return 0; |