avcodec/faxcompr: Check available bits in decode_uncompressed()

Fixes: Timeout
Fixes: 34950/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_TIFF_fuzzer-5686764151898112
Fixes: 34966/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_TIFF_fuzzer-4587409334468608

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

libavcodec/faxcompr.c

@@ -144,6 +144,8 @@ static int decode_uncompressed(AVCodecContext *avctx, GetBitContext *gb,
                 return AVERROR_INVALIDDATA;
             }
             cwi = 10 - av_log2(cwi);
+            if (get_bits_left(gb) < cwi + 1)
+                return AVERROR_INVALIDDATA;
             skip_bits(gb, cwi + 1);
             if (cwi > 5) {
                 newmode = get_bits1(gb);