[FFmpeg-cvslog] avcodec/hevcdec: Avoid only partly skiping duplicate first slices

[Michael Niedermayer]

ffmpeg | branch: release/4.1 | Michael Niedermayer <michael at niedermayer.cc> | Sat Mar 23 20:55:08 2019 +0100| [f1ecebcdb72b5928b585ec8f07c3847927b4bf1d] | committer: Michael Niedermayer

avcodec/hevcdec: Avoid only partly skiping duplicate first slices

Fixes: NULL pointer dereference and out of array access
Fixes: 13871/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_HEVC_fuzzer-5746167087890432
Fixes: 13845/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_HEVC_fuzzer-5650370728034304

This also fixes the return code for explode mode

Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
Reviewed-by: James Almer <jamrial at gmail.com>
Signed-off-by: Michael Niedermayer <michael at niedermayer.cc>
(cherry picked from commit 54655623a82632e7624714d7b2a3e039dc5faa7e)
Signed-off-by: Michael Niedermayer <michael at niedermayer.cc>

> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=f1ecebcdb72b5928b585ec8f07c3847927b4bf1d
---

 libavcodec/hevcdec.c | 14 ++++++++++----
 1 file changed, 10 insertions(+), 4 deletions(-)

diff --git a/libavcodec/hevcdec.c b/libavcodec/hevcdec.c
index 0dee673dac..afb3b1b554 100644
--- a/libavcodec/hevcdec.c
+++ b/libavcodec/hevcdec.c
@@ -485,6 +485,11 @@ static int hls_slice_header(HEVCContext *s)
 
     // Coded parameters
     sh->first_slice_in_pic_flag = get_bits1(gb);
+    if (s->ref && sh->first_slice_in_pic_flag) {
+        av_log(s->avctx, AV_LOG_ERROR, "Two slices reporting being the first in the same frame.\n");
+        return 1; // This slice will be skiped later, do not corrupt state
+    }
+
     if ((IS_IDR(s) || IS_BLA(s)) && sh->first_slice_in_pic_flag) {
         s->seq_decode = (s->seq_decode + 1) & 0xff;
         s->max_ra     = INT_MAX;
@@ -2915,6 +2920,11 @@ static int decode_nal_unit(HEVCContext *s, const H2645NAL *nal)
         ret = hls_slice_header(s);
         if (ret < 0)
             return ret;
+        if (ret == 1) {
+            ret = AVERROR_INVALIDDATA;
+            goto fail;
+        }
+
 
         if (
             (s->avctx->skip_frame >= AVDISCARD_BIDIR && s->sh.slice_type == HEVC_SLICE_B) ||
@@ -2924,10 +2934,6 @@ static int decode_nal_unit(HEVCContext *s, const H2645NAL *nal)
         }
 
         if (s->sh.first_slice_in_pic_flag) {
-            if (s->ref) {
-                av_log(s->avctx, AV_LOG_ERROR, "Two slices reporting being the first in the same frame.\n");
-                goto fail;
-            }
             if (s->max_ra == INT_MAX) {
                 if (s->nal_unit_type == HEVC_NAL_CRA_NUT || IS_BLA(s)) {
                     s->max_ra = s->poc;