From 2f014567cfd63e58156f60666f1a61ba147276ab Mon Sep 17 00:00:00 2001 From: Xi Wang Date: Tue, 22 Jan 2013 20:58:07 -0500 Subject: [PATCH] rtpenc: fix overflow checking in avc_mp4_find_startcode() The check `start + res < start' is broken since pointer overflow is undefined behavior in C. Many compilers such as gcc/clang optimize away this check. Use `res > end - start' instead. Also change `res' to unsigned int to avoid signed left-shift overflow. Signed-off-by: Xi Wang Signed-off-by: Michael Niedermayer --- libavformat/rtpenc_h264.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/libavformat/rtpenc_h264.c b/libavformat/rtpenc_h264.c index 68f497590b014..b6c16e17d8aa5 100644 --- a/libavformat/rtpenc_h264.c +++ b/libavformat/rtpenc_h264.c @@ -31,14 +31,14 @@ static const uint8_t *avc_mp4_find_startcode(const uint8_t *start, const uint8_t *end, int nal_length_size) { - int res = 0; + unsigned int res = 0; if (end - start < nal_length_size) return NULL; while (nal_length_size--) res = (res << 8) | *start++; - if (start + res > end || res < 0 || start + res < start) + if (res > end - start) return NULL; return start + res;