On 28.04.2015 22:21, Michael Niedermayer wrote:
> On Tue, Apr 28, 2015 at 08:57:39PM +0200, Andreas Cadhalpun wrote:
>> 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.cadhal...@googlemail.com>
>> ---
>> libavformat/nutdec.c | 2 +-
>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/libavformat/nutdec.c b/libavformat/nutdec.c
>> index 1bb2091..46946d3 100644
>> --- a/libavformat/nutdec.c
>> +++ b/libavformat/nutdec.c
>> @@ -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 || (i > 'N' && count > 256 - i) || (i <= 'N' &&
>> count > 255 - i)) {
>
> this could be simplfied to:
>
> if (count <= 0 || count > 256 - (i <= 'N') - i)) {
^
OK, but there is a bracket too much.
New patch attached.
Best regards,
Andreas
>From 95cc0bb685be1436e0689ea77daa3c63d691ecd4 Mon Sep 17 00:00:00 2001
From: Andreas Cadhalpun <andreas.cadhal...@googlemail.com>
Date: Tue, 28 Apr 2015 22:37:19 +0200
Subject: [PATCH] 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.cadhal...@googlemail.com>
---
libavformat/nutdec.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/libavformat/nutdec.c b/libavformat/nutdec.c
index 74e3637..6f615c2 100644
--- a/libavformat/nutdec.c
+++ b/libavformat/nutdec.c
@@ -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;
}
--
2.1.4
_______________________________________________
ffmpeg-devel mailing list
ffmpeg-devel@ffmpeg.org
http://ffmpeg.org/mailman/listinfo/ffmpeg-devel
