nutdec: fix illegal count check in decode_main_header

The existing check has two problems:
 1) i + count can overflow, so that the check '< 256' returns true.
 2) In the (i == 'N') case occurs a j-- so that the loop runs once more.

This can trigger the assertion 'nut->header_len[0] == 0' or cause
segmentation faults or infinite hangs.

Signed-off-by: Andreas Cadhalpun <Andreas.Cadhalpun@googlemail.com>
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
This commit is contained in:
Andreas Cadhalpun 2015-04-28 22:37:19 +02:00 committed by Michael Niedermayer
parent 361702660d
commit 7c24ca1bda
1 changed files with 1 additions and 1 deletions

View File

@ -294,7 +294,7 @@ static int decode_main_header(NUTContext *nut)
while (tmp_fields-- > 8)
ffio_read_varlen(bc);
if (count == 0 || i + count > 256) {
if (count <= 0 || count > 256 - (i <= 'N') - i) {
av_log(s, AV_LOG_ERROR, "illegal count %d at %d\n", count, i);
return AVERROR_INVALIDDATA;
}