[FFmpeg-cvslog] avcodec/faxcompr: Check if bits are available before reading in cmode == 9 || cmode == 10

[Michael Niedermayer]

ffmpeg | branch: master | Michael Niedermayer <michael at niedermayer.cc> | Wed Jun  9 21:20:04 2021 +0200| [7d8421e3d5bc1300687a65384baccbcb3874b7ac] | committer: Michael Niedermayer

avcodec/faxcompr: Check if bits are available before reading in cmode == 9 || cmode == 10

Fixes: Timeout
Fixes: 34950/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_TIFF_fuzzer-5686764151898112

Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
Signed-off-by: Michael Niedermayer <michael at niedermayer.cc>

> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=7d8421e3d5bc1300687a65384baccbcb3874b7ac
---

 libavcodec/faxcompr.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/libavcodec/faxcompr.c b/libavcodec/faxcompr.c
index d44de2485d..45e0c482d7 100644
--- a/libavcodec/faxcompr.c
+++ b/libavcodec/faxcompr.c
@@ -304,7 +304,10 @@ static int decode_group3_2d_line(AVCodecContext *avctx, GetBitContext *gb,
                 mode = !mode;
             }
         } else if (cmode == 9 || cmode == 10) {
-            int xxx = get_bits(gb, 3);
+            int xxx;
+            if (get_bits_left(gb) < 3)
+                return AVERROR_INVALIDDATA;
+            xxx = get_bits(gb, 3);
             if (cmode == 9 && xxx == 7) {
                 int ret;
                 int pix_left = width - offs;