From 22e960ad478e568f4094971a58c6ad8f549c0180 Mon Sep 17 00:00:00 2001 From: Andreas Cadhalpun Date: Sun, 13 Dec 2015 21:02:16 +0100 Subject: [PATCH] golomb: always check for invalid UE golomb codes in get_ue_golomb Also correct the check to reject log < 7, because UPDATE_CACHE only guarantees 25 meaningful bits. This fixes undefined behavior: runtime error: shift exponent is negative Testing with START/STOP timers in get_ue_golomb, one for the first branch (A) and one for the second (B), shows that there is practically no slowdown, e.g. for the cavs decoder: With the check in the B branch: 629 decicycles in get_ue_golomb B, 4194260 runs, 44 skips 433 decicycles in get_ue_golomb A,268434102 runs, 1354 skips Without the check: 624 decicycles in get_ue_golomb B, 4194273 runs, 31 skips 433 decicycles in get_ue_golomb A,268434203 runs, 1253 skips Since the B branch is executed far less often than the A branch, this change is negligible, even more so for the h264 decoder, where the ratio B/A is a lot smaller. Fixes: mozilla bug 1230239 Fixes: fbeb8b2c7c996e9b91c6b1af319d7ebc/asan_heap-oob_195450f_2743_e8856ece4579ea486670be2b236099a0.bit Found-by: Tyson Smith Found-by: Mateusz "j00ru" Jurczyk and Gynvael Coldwind Reviewed-by: Michael Niedermayer Signed-off-by: Andreas Cadhalpun --- libavcodec/golomb.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/libavcodec/golomb.h b/libavcodec/golomb.h index d30bb6bc86..5136a04845 100644 --- a/libavcodec/golomb.h +++ b/libavcodec/golomb.h @@ -68,7 +68,7 @@ static inline int get_ue_golomb(GetBitContext *gb) int log = 2 * av_log2(buf) - 31; LAST_SKIP_BITS(re, gb, 32 - log); CLOSE_READER(re, gb); - if (CONFIG_FTRAPV && log < 0) { + if (log < 7) { av_log(NULL, AV_LOG_ERROR, "Invalid UE golomb code\n"); return AVERROR_INVALIDDATA; }