From 404ca80eb5c2727d78cd517d12108b040c522e12 Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Sat, 19 Apr 2014 10:15:07 -0700 Subject: [PATCH] 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 Diagnosed-by: Hugh Dickins Acked-by: Oleg Nesterov Cc: Neil Horman Cc: Andrew Morton Cc: stable@vger.kernel.org # 3.11+ Signed-off-by: Linus Torvalds --- fs/coredump.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) 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;