Code:  static void add_bytes_c(uint8_t *dst, uint8_t *src, int w){
     long i;
    for(i=0; i<=w-sizeof(long); i+=sizeof(long)){
         long a = *(long*)(src+i);
         long b = *(long*)(dst+i);
         *(long*)(dst+i) = ((a&pb_7f) + (b&pb_7f)) ^ ((a^b)&pb_80);
    }
    for(; i<w; i++)
        dst[i+0] += src[i+0];
}

Vulnerability Type: DoS 
CWE ID: CWE-189
Summary: Multiple integer signedness errors in libavcodec/dsputil.c in FFmpeg before 2.1 allow remote attackers to cause a denial of service (out-of-bounds array access) or possibly have unspecified other impact via crafted data.
Commit Message: avcodec/dsputil: fix signedness in sizeof() comparissions

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>