[FFmpeg-cvslog] avcodec/proresdec: Consider negative bits left

[Michael Niedermayer]

ffmpeg | branch: release/4.2 | Michael Niedermayer <michael at niedermayer.cc> | Fri Jul 19 19:21:41 2024 +0200| [11834dcd8baf4d17504bcf724940718288b60fa5] | committer: Michael Niedermayer

avcodec/proresdec: Consider negative bits left

Fixes: 70036/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_PRORES_fuzzer-6298797647396864
Fixes: shift exponent 40 is too large for 32-bit type 'uint32_t' (aka 'unsigned int')

Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
Signed-off-by: Michael Niedermayer <michael at niedermayer.cc>
(cherry picked from commit 419eee63565f81aca67b29582297841c59deaab8)
Signed-off-by: Michael Niedermayer <michael at niedermayer.cc>

> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=11834dcd8baf4d17504bcf724940718288b60fa5
---

 libavcodec/proresdec2.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/libavcodec/proresdec2.c b/libavcodec/proresdec2.c
index 2652a31c81..8365f0d3dc 100644
--- a/libavcodec/proresdec2.c
+++ b/libavcodec/proresdec2.c
@@ -488,7 +488,7 @@ static av_always_inline int decode_ac_coeffs(AVCodecContext *avctx, GetBitContex
 
     for (pos = block_mask;;) {
         bits_left = gb->size_in_bits - re_index;
-        if (!bits_left || (bits_left < 32 && !SHOW_UBITS(re, gb, bits_left)))
+        if (bits_left <= 0 || (bits_left < 32 && !SHOW_UBITS(re, gb, bits_left)))
             break;
 
         DECODE_CODEWORD(run, run_to_cb[FFMIN(run,  15)], LAST_SKIP_BITS);