[FFmpeg-cvslog] swscale: take first/lastline over/underflows into account for MMX.

[Ronald S. Bultje]

ffmpeg | branch: release/0.8 | Ronald S. Bultje <rsbultje at gmail.com> | Wed Feb 22 16:48:38 2012 -0800| [0fe53216340e2bab1bb07df6fcdc14f742f3e69c] | committer: Reinhard Tartler

swscale: take first/lastline over/underflows into account for MMX.

Fixes crashes for extremely large resizes (several 100-fold).

Found-by: Mateusz "j00ru" Jurczyk and Gynvael Coldwind
CC: libav-stable at libav.org
(cherry picked from commit 1d8c4af396b6ed84c84b5ebf0bf1163c4a7a3017)

Signed-off-by: Anton Khirnov <anton at khirnov.net>
Signed-off-by: Reinhard Tartler <siretart at tauware.de>

> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=0fe53216340e2bab1bb07df6fcdc14f742f3e69c
---

 libswscale/x86/swscale_mmx.c |   38 ++++++++++++++++++++++++++++++++++++++
 1 files changed, 38 insertions(+), 0 deletions(-)

diff --git a/libswscale/x86/swscale_mmx.c b/libswscale/x86/swscale_mmx.c
index f855a75..a245106 100644
--- a/libswscale/x86/swscale_mmx.c
+++ b/libswscale/x86/swscale_mmx.c
@@ -132,6 +132,44 @@ void updateMMXDitherTables(SwsContext *c, int dstY, int lumBufIndex, int chrBufI
         const int16_t **chrUSrcPtr= (const int16_t **) chrUPixBuf + chrBufIndex + firstChrSrcY - lastInChrBuf + vChrBufSize;
         const int16_t **alpSrcPtr= (CONFIG_SWSCALE_ALPHA && alpPixBuf) ? (const int16_t **) alpPixBuf + lumBufIndex + firstLumSrcY - lastInLumBuf + vLumBufSize : NULL;
         int i;
+
+        if (firstLumSrcY < 0 || firstLumSrcY + vLumFilterSize > c->srcH) {
+            const int16_t **tmpY = (const int16_t **) lumPixBuf + 2 * vLumBufSize;
+            int neg = -firstLumSrcY, i, end = FFMIN(c->srcH - firstLumSrcY, vLumFilterSize);
+            for (i = 0; i < neg;            i++)
+                tmpY[i] = lumSrcPtr[neg];
+            for (     ; i < end;            i++)
+                tmpY[i] = lumSrcPtr[i];
+            for (     ; i < vLumFilterSize; i++)
+                tmpY[i] = tmpY[i-1];
+            lumSrcPtr = tmpY;
+
+            if (alpSrcPtr) {
+                const int16_t **tmpA = (const int16_t **) alpPixBuf + 2 * vLumBufSize;
+                for (i = 0; i < neg;            i++)
+                    tmpA[i] = alpSrcPtr[neg];
+                for (     ; i < end;            i++)
+                    tmpA[i] = alpSrcPtr[i];
+                for (     ; i < vLumFilterSize; i++)
+                    tmpA[i] = tmpA[i - 1];
+                alpSrcPtr = tmpA;
+            }
+        }
+        if (firstChrSrcY < 0 || firstChrSrcY + vChrFilterSize > c->chrSrcH) {
+            const int16_t **tmpU = (const int16_t **) chrUPixBuf + 2 * vChrBufSize;
+            int neg = -firstChrSrcY, i, end = FFMIN(c->chrSrcH - firstChrSrcY, vChrFilterSize);
+            for (i = 0; i < neg;            i++) {
+                tmpU[i] = chrUSrcPtr[neg];
+            }
+            for (     ; i < end;            i++) {
+                tmpU[i] = chrUSrcPtr[i];
+            }
+            for (     ; i < vChrFilterSize; i++) {
+                tmpU[i] = tmpU[i - 1];
+            }
+            chrUSrcPtr = tmpU;
+        }
+
         if (flags & SWS_ACCURATE_RND) {
             int s= APCK_SIZE / 8;
             for (i=0; i<vLumFilterSize; i+=2) {