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avcodec/rv34, mpegvideo: Fix segfault upon frame size change error

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The RealVideo 3.0 and 4.0 decoders call ff_mpv_common_init() only during
their init function and not during decode_frame(); when the size of the
frame changes, they call ff_mpv_common_frame_size_change(). Yet upon
error, said function calls ff_mpv_common_end() which frees the whole
MpegEncContext and not only those parts that
ff_mpv_common_frame_size_change() reinits. As a result, the context will
never be usable again; worse, because decode_frame() contains no check
for whether the context is initialized or not, it is presumed that it is
initialized, leading to segfaults. Basically the same happens if
rv34_decoder_realloc() fails.

This commit fixes this by only resetting the parts that
ff_mpv_common_frame_size_change() changes upon error and by actually
checking whether the context is in need of reinitialization in
ff_rv34_decode_frame().

Reviewed-by: Michael Niedermayer <michael@niedermayer.cc>
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
This commit is contained in:
Andreas Rheinhardt 2021-04-05 02:05:58 +02:00
parent 8ffd3ef9d9
commit 9abda1365c
2 changed files with 13 additions and 6 deletions

6
libavcodec/mpegvideo.c
View File

@ -555,7 +555,6 @@ int ff_mpeg_update_thread_context(AVCodecContext *dst,
}
if (s->height != s1->height || s->width != s1->width || s->context_reinit) {
s->context_reinit = 0;
s->height = s1->height;
s->width = s1->width;
if ((ret = ff_mpv_common_frame_size_change(s)) < 0)
@ -1099,10 +1098,12 @@ int ff_mpv_common_frame_size_change(MpegEncContext *s)
if (err < 0)
goto fail;
}
s->context_reinit = 0;
return 0;
fail:
ff_mpv_common_end(s);
free_context_frame(s);
s->context_reinit = 1;
return err;
}
@ -1149,6 +1150,7 @@ void ff_mpv_common_end(MpegEncContext *s)
av_frame_free(&s->new_picture.f);
s->context_initialized = 0;
s->context_reinit = 0;
s->last_picture_ptr =
s->next_picture_ptr =
s->current_picture_ptr = NULL;

13
libavcodec/rv34.c
View File

@ -1383,6 +1383,7 @@ static int rv34_decoder_alloc(RV34DecContext *r)
if (!(r->cbp_chroma && r->cbp_luma && r->deblock_coefs &&
r->intra_types_hist && r->mb_type)) {
r->s.context_reinit = 1;
rv34_decoder_free(r);
return AVERROR(ENOMEM);
}
@ -1530,7 +1531,7 @@ int ff_rv34_decode_update_thread_context(AVCodecContext *dst, const AVCodecConte
if (dst == src || !s1->context_initialized)
return 0;
if (s->height != s1->height || s->width != s1->width) {
if (s->height != s1->height || s->width != s1->width || s->context_reinit) {
s->height = s1->height;
s->width = s1->width;
if ((err = ff_mpv_common_frame_size_change(s)) < 0)
@ -1667,11 +1668,12 @@ int ff_rv34_decode_frame(AVCodecContext *avctx,
if (s->mb_num_left > 0 && s->current_picture_ptr) {
av_log(avctx, AV_LOG_ERROR, "New frame but still %d MB left.\n",
s->mb_num_left);
ff_er_frame_end(&s->er);
if (!s->context_reinit)
ff_er_frame_end(&s->er);
ff_mpv_frame_end(s);
}
if (s->width != si.width || s->height != si.height) {
if (s->width != si.width || s->height != si.height || s->context_reinit) {
int err;
av_log(s->avctx, AV_LOG_WARNING, "Changing dimensions to %dx%d\n",
@ -1689,7 +1691,6 @@ int ff_rv34_decode_frame(AVCodecContext *avctx,
err = ff_set_dimensions(s->avctx, s->width, s->height);
if (err < 0)
return err;
if ((err = ff_mpv_common_frame_size_change(s)) < 0)
return err;
if ((err = rv34_decoder_realloc(r)) < 0)
@ -1744,6 +1745,10 @@ int ff_rv34_decode_frame(AVCodecContext *avctx,
}
s->mb_x = s->mb_y = 0;
ff_thread_finish_setup(s->avctx);
} else if (s->context_reinit) {
av_log(s->avctx, AV_LOG_ERROR, "Decoder needs full frames to "
"reinitialize (start MB is %d).\n", si.start);
return AVERROR_INVALIDDATA;
} else if (HAVE_THREADS &&
(s->avctx->active_thread_type & FF_THREAD_FRAME)) {
av_log(s->avctx, AV_LOG_ERROR, "Decoder needs full frames in frame "