[FFmpeg-devel] [PATCH 1/2] avcodec/hevc/hevcdec: ensure a bit was read when checking for alignment_bit_equal_to_one

[FFmpeg-devel] [PATCH 1/2] avcodec/hevc/hevcdec: ensure a bit was read when checking for alignment_bit_equal_to_one

[James Almer]

Prevents printing bogus errors about the value being 0, when in fact we
overread the available slice buffer.

Signed-off-by: James Almer <jamrial@gmail.com>
---
 libavcodec/hevc/hevcdec.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/libavcodec/hevc/hevcdec.c b/libavcodec/hevc/hevcdec.c
index 83acf3511f..df186d6194 100644
--- a/libavcodec/hevc/hevcdec.c
+++ b/libavcodec/hevc/hevcdec.c
@@ -1154,7 +1154,7 @@ static int hls_slice_header(SliceHeader *sh, const HEVCContext *s, GetBitContext
     }
 
     ret = get_bits1(gb);
-    if (!ret) {
+    if (!ret && get_bits_left(gb) >= 0) {
         av_log(s->avctx, AV_LOG_ERROR, "alignment_bit_equal_to_one=0\n");
         return AVERROR_INVALIDDATA;
     }
-- 
2.49.0

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[FFmpeg-devel] [PATCH 2/2] avcodec/hevc/hevcdec: move the slice header buffer overread check up in the function

[James Almer]

Abort as soon as we're done reading the slice header instead of running extra checks
that assume slice data may follow.

Signed-off-by: James Almer <jamrial@gmail.com>
---
 libavcodec/hevc/hevcdec.c | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/libavcodec/hevc/hevcdec.c b/libavcodec/hevc/hevcdec.c
index df186d6194..a7a91769fe 100644
--- a/libavcodec/hevc/hevcdec.c
+++ b/libavcodec/hevc/hevcdec.c
@@ -1160,6 +1160,12 @@ static int hls_slice_header(SliceHeader *sh, const HEVCContext *s, GetBitContext
     }
     sh->data_offset = align_get_bits(gb) - gb->buffer;
 
+    if (get_bits_left(gb) < 0) {
+        av_log(s->avctx, AV_LOG_ERROR,
+               "Overread slice header by %d bits\n", -get_bits_left(gb));
+        return AVERROR_INVALIDDATA;
+    }
+
     // Inferred parameters
     sh->slice_qp = 26U + pps->pic_init_qp_minus26 + sh->slice_qp_delta;
     if (sh->slice_qp > 51 ||
@@ -1180,12 +1186,6 @@ static int hls_slice_header(SliceHeader *sh, const HEVCContext *s, GetBitContext
         return AVERROR_INVALIDDATA;
     }
 
-    if (get_bits_left(gb) < 0) {
-        av_log(s->avctx, AV_LOG_ERROR,
-               "Overread slice header by %d bits\n", -get_bits_left(gb));
-        return AVERROR_INVALIDDATA;
-    }
-
     return 0;
 }
 
-- 
2.49.0

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