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vp8: change mv_{min,max}.{x,y} type to int

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If one of the dimensions is larger than 8176, s->mb_width or
s->mb_height is larger than 511, leading to an int16_t overflow of
s->mv_max.{x,y}. This then causes av_clip to be called with amin > amax.

Changing the type to int avoids the overflow and has no negative
effect, because s->mv_max is only used in clamp_mv for clipping.
Since mv_max.{x,y} is positive and mv_min.{x,y} negative, av_clip can't
increase the absolute value. The input to av_clip is an int16_t, and
thus the output fits into int16_t as well.

For additional safety, s->mv_{min,max}.{x,y} are clipped to int16_t range
before use.

Reviewed-by: Ronald S. Bultje <rsbultje@gmail.com>
Signed-off-by: Andreas Cadhalpun <Andreas.Cadhalpun@googlemail.com>
This commit is contained in:
Andreas Cadhalpun 2015-06-08 22:38:29 +02:00
parent 1382add59d
commit 6fdbaa2b7f
2 changed files with 11 additions and 4 deletions
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6
libavcodec/vp8.c
View File

@ -757,8 +757,10 @@ static int vp8_decode_frame_header(VP8Context *s, const uint8_t *buf, int buf_si
static av_always_inline
void clamp_mv(VP8Context *s, VP56mv *dst, const VP56mv *src)
{
dst->x = av_clip(src->x, s->mv_min.x, s->mv_max.x);
dst->y = av_clip(src->y, s->mv_min.y, s->mv_max.y);
dst->x = av_clip(src->x, av_clip(s->mv_min.x, INT16_MIN, INT16_MAX),
av_clip(s->mv_max.x, INT16_MIN, INT16_MAX));
dst->y = av_clip(src->y, av_clip(s->mv_min.y, INT16_MIN, INT16_MAX),
av_clip(s->mv_max.y, INT16_MIN, INT16_MAX));
}
/**

9
libavcodec/vp8.h
View File

@ -134,6 +134,11 @@ typedef struct VP8Frame {
AVBufferRef *seg_map;
} VP8Frame;
typedef struct VP8intmv {
int x;
int y;
} VP8intmv;
#define MAX_THREADS 8
typedef struct VP8Context {
VP8ThreadData *thread_data;
@ -152,8 +157,8 @@ typedef struct VP8Context {
uint8_t deblock_filter;
uint8_t mbskip_enabled;
uint8_t profile;
VP56mv mv_min;
VP56mv mv_max;
VP8intmv mv_min;
VP8intmv mv_max;
int8_t sign_bias[4]; ///< one state [0, 1] per ref frame type
int ref_count[3];