[Ffmpeg-devel] [PATCH] fix ffmpeg crash when thread_count is zero

[Limin Wang]

Hi,

I have figured out the root cause of the crash, please review the
attached patch. It's a corner case for some part of context weren't
initialized in case thread_count is zero.


Thanks,
Limin
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Index: libavcodec/mpegvideo.c
===================================================================
--- libavcodec/mpegvideo.c	(revision 8146)
+++ libavcodec/mpegvideo.c	(working copy)
@@ -825,7 +825,12 @@
         memcpy(s->thread_context[i], s, sizeof(MpegEncContext));
     }
 
-    for(i=0; i<s->avctx->thread_count; i++){
+    if(init_duplicate_context(s->thread_context[0], s) < 0)
+        goto fail;
+    s->thread_context[0]->start_mb_y= 0;
+    s->thread_context[0]->end_mb_y  = s->mb_height;
+
+    for(i=1; i<s->avctx->thread_count; i++){
         if(init_duplicate_context(s->thread_context[i], s) < 0)
            goto fail;
         s->thread_context[i]->start_mb_y= (s->mb_height*(i  ) + s->avctx->thread_count/2) / s->avctx->thread_count;
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