nutdec: reject negative value_len in read_sm_data
authorAndreas Cadhalpun <Andreas.Cadhalpun@googlemail.com>
Sat, 19 Dec 2015 11:02:56 +0000 (12:02 +0100)
committerAndreas Cadhalpun <Andreas.Cadhalpun@googlemail.com>
Sun, 20 Dec 2015 15:13:44 +0000 (16:13 +0100)
If it is negative, it can cause the byte position to move backwards in
avio_skip, which in turn makes sm_size negative and thus size larger
than the size of the packet buffer, causing invalid writes in avio_read.

Also fix potential overflow of avio_tell(bc) + value_len.

Reviewed-by: Michael Niedermayer <michael@niedermayer.cc>
Signed-off-by: Andreas Cadhalpun <Andreas.Cadhalpun@googlemail.com>
(cherry picked from commit ce10f572c12b0d172c72d31d8c979afce602bf0c)
Signed-off-by: Andreas Cadhalpun <Andreas.Cadhalpun@googlemail.com>
libavformat/nutdec.c

index eec6423..df371da 100644 (file)
@@ -885,7 +885,7 @@ static int read_sm_data(AVFormatContext *s, AVIOContext *bc, AVPacket *pkt, int
 
             get_str(bc, type_str, sizeof(type_str));
             value_len = ffio_read_varlen(bc);
-            if (avio_tell(bc) + value_len >= maxpos)
+            if (value_len < 0 || value_len >= maxpos - avio_tell(bc))
                 return AVERROR_INVALIDDATA;
             if (!strcmp(name, "Palette")) {
                 dst = av_packet_new_side_data(pkt, AV_PKT_DATA_PALETTE, value_len);