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vc1dec: fix invalid memory access for small video dimensions

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For small video dimensions, these calculations of the upper bound
for pixel access may have a negative result. Using an unsigned
comparison to bound a potentially negative value only works if
the greater operand is non-negative. Fixed by doing edge emulation
when the upper bound is probably negative, everywhere that this
pattern appears.

Signed-off-by: Kostya Shishkov <kostya.shishkov@gmail.com>
This commit is contained in:
John Brooks 2011-12-11 02:37:21 -07:00 committed by Kostya Shishkov
parent aacf6b3a2f
commit d209c27b09
1 changed files with 5 additions and 1 deletions
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6
libavcodec/vc1dec.c
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@ -568,6 +568,7 @@ static void vc1_mc_1mv(VC1Context *v, int dir)
}
if (v->rangeredfrm || (v->mv_mode == MV_PMODE_INTENSITY_COMP)
|| s->h_edge_pos < 22 || v_edge_pos < 22
|| (unsigned)(src_x - s->mspel) > s->h_edge_pos - (mx&3) - 16 - s->mspel * 3
|| (unsigned)(src_y - s->mspel) > v_edge_pos - (my&3) - 16 - s->mspel * 3) {
uint8_t *uvbuf = s->edge_emu_buffer + 19 * s->linesize;
@ -799,6 +800,7 @@ static void vc1_mc_4mv_luma(VC1Context *v, int n, int dir)
if (fieldmv && (src_y & 1) && src_y < 4)
src_y--;
if (v->rangeredfrm || (v->mv_mode == MV_PMODE_INTENSITY_COMP)
|| s->h_edge_pos < 13 || v_edge_pos < 23
|| (unsigned)(src_x - s->mspel) > s->h_edge_pos - (mx & 3) - 8 - s->mspel * 2
|| (unsigned)(src_y - (s->mspel << fieldmv)) > v_edge_pos - (my & 3) - ((8 + s->mspel * 2) << fieldmv)) {
srcY -= s->mspel * (1 + (s->linesize << fieldmv));
@ -998,6 +1000,7 @@ static void vc1_mc_4mv_chroma(VC1Context *v, int dir)
}
if (v->rangeredfrm || (v->mv_mode == MV_PMODE_INTENSITY_COMP)
|| s->h_edge_pos < 18 || v_edge_pos < 18
|| (unsigned)uvsrc_x > (s->h_edge_pos >> 1) - 9
|| (unsigned)uvsrc_y > (v_edge_pos >> 1) - 9) {
s->dsp.emulated_edge_mc(s->edge_emu_buffer , srcU, s->uvlinesize,
@ -1102,6 +1105,7 @@ static void vc1_mc_4mv_chroma4(VC1Context *v)
if (fieldmv && (uvsrc_y & 1) && uvsrc_y < 2)
uvsrc_y--;
if ((v->mv_mode == MV_PMODE_INTENSITY_COMP)
|| s->h_edge_pos < 10 || v_edge_pos < (5 << fieldmv)
|| (unsigned)uvsrc_x > (s->h_edge_pos >> 1) - 5
|| (unsigned)uvsrc_y > v_edge_pos - (5 << fieldmv)) {
s->dsp.emulated_edge_mc(s->edge_emu_buffer, srcU, s->uvlinesize,
@ -2006,7 +2010,7 @@ static void vc1_interp_mc(VC1Context *v)
srcV = s->edge_emu_buffer + 18 * s->linesize;
}
if (v->rangeredfrm
if (v->rangeredfrm || s->h_edge_pos < 22 || v_edge_pos < 22
|| (unsigned)(src_x - s->mspel) > s->h_edge_pos - (mx & 3) - 16 - s->mspel * 3
|| (unsigned)(src_y - s->mspel) > v_edge_pos - (my & 3) - 16 - s->mspel * 3) {
uint8_t *uvbuf = s->edge_emu_buffer + 19 * s->linesize;