[FFmpeg-devel] [PATCH 1/2] avcodec/av1: only set the private context pix_fmt field if get_pixel_format() succeeds

[FFmpeg-devel] [PATCH 1/2] avcodec/av1: only set the private context pix_fmt field if get_pixel_format() succeeds

[James Almer]

Otherwise get_pixel_format() will not be called when parsing a subsequent Sequence
Header in non hwaccel enabled scenarios, allowing frame parsing when it shouldn't.

This prevents the scenario seqhdr -> frame_hdr/redundant_frame_hdr -> seqhdr ->
redundant_frame_hdr from having the latter redundant frame header parsed as if it
was a frame header by the decoder because the former was discarded.
Since CBS did not discard it, the latter redundant frame header is output with a
zeroed AV1RawFrameHeader struct, which can have undesired results, like division
by zero with fields normally guaranteed to be anything else.

Signed-off-by: James Almer <jamrial@gmail.com>
---
 libavcodec/av1dec.c | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/libavcodec/av1dec.c b/libavcodec/av1dec.c
index 613efc5d11..727d829e5b 100644
--- a/libavcodec/av1dec.c
+++ b/libavcodec/av1dec.c
@@ -506,9 +506,8 @@ static int get_pixel_format(AVCodecContext *avctx)
 
     if (pix_fmt == AV_PIX_FMT_NONE)
         return -1;
-    s->pix_fmt = pix_fmt;
 
-    switch (s->pix_fmt) {
+    switch (pix_fmt) {
     case AV_PIX_FMT_YUV420P:
 #if CONFIG_AV1_DXVA2_HWACCEL
         *fmtp++ = AV_PIX_FMT_DXVA2_VLD;
@@ -551,7 +550,7 @@ static int get_pixel_format(AVCodecContext *avctx)
         break;
     }
 
-    *fmtp++ = s->pix_fmt;
+    *fmtp++ = pix_fmt;
     *fmtp = AV_PIX_FMT_NONE;
 
     ret = ff_thread_get_format(avctx, pix_fmts);
@@ -569,7 +568,7 @@ static int get_pixel_format(AVCodecContext *avctx)
         return AVERROR(ENOSYS);
     }
 
-    avctx->pix_fmt = ret;
+    avctx->pix_fmt = s->pix_fmt = ret;
 
     return 0;
 }
-- 
2.35.1

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[FFmpeg-devel] [PATCH 2/2] Revert "avcodec/av1dec: Check tile_cols"

[James Almer]

This reverts commit 4fdfe430c12225e819f68993474bd2f473c7e8b1.

The previous commit ensures this field will never be zero.
---
 libavcodec/av1dec.c | 3 ---
 1 file changed, 3 deletions(-)

diff --git a/libavcodec/av1dec.c b/libavcodec/av1dec.c
index 727d829e5b..0543452b06 100644
--- a/libavcodec/av1dec.c
+++ b/libavcodec/av1dec.c
@@ -398,9 +398,6 @@ static int get_tiles_info(AVCodecContext *avctx, const AV1RawTileGroup *tile_gro
     s->tg_start = tile_group->tg_start;
     s->tg_end = tile_group->tg_end;
 
-    if (s->raw_frame_header->tile_cols == 0)
-        return AVERROR_INVALIDDATA;
-
     for (tile_num = tile_group->tg_start; tile_num <= tile_group->tg_end; tile_num++) {
         tile_row = tile_num / s->raw_frame_header->tile_cols;
         tile_col = tile_num % s->raw_frame_header->tile_cols;
-- 
2.35.1

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Re: [FFmpeg-devel] [PATCH 1/2] avcodec/av1: only set the private context pix_fmt field if get_pixel_format() succeeds

[Michael Niedermayer]

[-- Attachment #1.1: Type: text/plain, Size: 1137 bytes --]

On Tue, Mar 22, 2022 at 04:10:59PM -0300, James Almer wrote:
> Otherwise get_pixel_format() will not be called when parsing a subsequent Sequence
> Header in non hwaccel enabled scenarios, allowing frame parsing when it shouldn't.
> 
> This prevents the scenario seqhdr -> frame_hdr/redundant_frame_hdr -> seqhdr ->
> redundant_frame_hdr from having the latter redundant frame header parsed as if it
> was a frame header by the decoder because the former was discarded.
> Since CBS did not discard it, the latter redundant frame header is output with a
> zeroed AV1RawFrameHeader struct, which can have undesired results, like division
> by zero with fields normally guaranteed to be anything else.
> 
> Signed-off-by: James Almer <jamrial@gmail.com>
> ---
>  libavcodec/av1dec.c | 7 +++----
>  1 file changed, 3 insertions(+), 4 deletions(-)

This patchset fixes the 2 issues too

thx

[...]
-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

Its not that you shouldnt use gotos but rather that you should write
readable code and code with gotos often but not always is less readable

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[-- Attachment #2: Type: text/plain, Size: 251 bytes --]

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