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mpegvideo: Fix long standing race condition with frame threads

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Since resolution change support this also was exploitable, which is
how it was found.

Fixes read after free and out of array reads.

Found-by: Mateusz "j00ru" Jurczyk and Gynvael Coldwind
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
This commit is contained in:
Michael Niedermayer 2013-01-15 04:58:22 +01:00
parent df4203ac6f
commit 8ac8f04993
2 changed files with 10 additions and 3 deletions
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9
libavcodec/mpegvideo.c
View File

@ -223,6 +223,7 @@ void ff_copy_picture(Picture *dst, Picture *src)
*/
static void free_frame_buffer(MpegEncContext *s, Picture *pic)
{
pic->period_since_free = 0;
/* WM Image / Screen codecs allocate internal buffers with different
* dimensions / colorspaces; ignore user-defined callbacks for these. */
if (s->codec_id != AV_CODEC_ID_WMV3IMAGE &&
@ -611,8 +612,10 @@ int ff_mpeg_update_thread_context(AVCodecContext *dst,
(char *) &s1->last_picture_ptr - (char *) &s1->last_picture);
// reset s->picture[].f.extended_data to s->picture[].f.data
for (i = 0; i < s->picture_count; i++)
for (i = 0; i < s->picture_count; i++) {
s->picture[i].f.extended_data = s->picture[i].f.data;
s->picture[i].period_since_free ++;
}
s->last_picture_ptr = REBASE_PICTURE(s1->last_picture_ptr, s, s1);
s->current_picture_ptr = REBASE_PICTURE(s1->current_picture_ptr, s, s1);
@ -1258,6 +1261,10 @@ void ff_release_unused_pictures(MpegEncContext*s, int remove_current)
static inline int pic_is_unused(MpegEncContext *s, Picture *pic)
{
if ( (s->avctx->active_thread_type & FF_THREAD_FRAME)
&& pic->f.qscale_table //check if the frame has anything allocated
&& pic->period_since_free < s->avctx->thread_count)
return 0;
if (pic->f.data[0] == NULL)
return 1;
if (pic->needs_realloc && !(pic->f.reference & DELAYED_PIC_REF))

4
libavcodec/mpegvideo.h
View File

@ -60,8 +60,7 @@ enum OutputFormat {
#define MAX_MV 2048
#define MAX_THREADS 32
#define MAX_PICTURE_COUNT 34
#define MAX_PICTURE_COUNT 36
#define ME_MAP_SIZE 64
#define ME_MAP_SHIFT 3
@ -149,6 +148,7 @@ typedef struct Picture{
int b_frame_score; /* */
struct MpegEncContext *owner2; ///< pointer to the MpegEncContext that allocated this picture
int needs_realloc; ///< Picture needs to be reallocated (eg due to a frame size change)
int period_since_free; ///< "cycles" since this Picture has been freed
} Picture;
/**