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authorEric Dumazet <edumazet@google.com>2014-04-19 10:15:07 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2014-04-19 13:23:31 -0700
commit404ca80eb5c2727d78cd517d12108b040c522e12 (patch)
tree0ff760410325ec53b260f16d844969965921c793
parent6d4596905b65bf4c63c1a008f50bf385fa49f19b (diff)
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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.c7
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;