On 09.11.2016 11:10, Michael Niedermayer wrote:
> On Wed, Nov 09, 2016 at 01:11:29AM +0100, Andreas Cadhalpun wrote:
>> Otherwise put_bits can be called with a value that doesn't fit in the
>> sample_len, causing an assertion failure.
>> ---
>> libavcodec/pnmdec.c | 4 ++++
>> 1 file changed, 4 insertions(+)
>>
>> diff --git a/libavcodec/pnmdec.c b/libavcodec/pnmdec.c
>> index ca97cc3..0381ea6 100644
>> --- a/libavcodec/pnmdec.c
>> +++ b/libavcodec/pnmdec.c
>> @@ -145,6 +145,10 @@ static int pnm_decode_frame(AVCodecContext *avctx, void
>> *data,
>> /* read a sequence of digits */
>> do {
>> v = 10*v + c;
>> + if (v > s->maxval) {
>> + av_log(avctx, AV_LOG_ERROR, "value %d
>> larger than maxval %d\n", v, s->maxval);
>> + return AVERROR_INVALIDDATA;
>> + }
>
> indention is a bit noisy
Fixed.
> i think it can overflow if maxval is large,
I've added an explicit check for v < 0, which should catch that.
> it would be faster to check outside the loop
However, such a check could pass if v overflowed so much that it's
in the valid range again, so I'd rather not do that.
Updated patch is attached.
Best regards,
Andreas
>From 7e9dcbde04ad95fc93ac2f0e91d734c8187c8d2b Mon Sep 17 00:00:00 2001
From: Andreas Cadhalpun <[email protected]>
Date: Wed, 9 Nov 2016 01:09:35 +0100
Subject: [PATCH] pnmdec: make sure v is capped by maxval
Otherwise put_bits can be called with a value that doesn't fit in the
sample_len, causing an assertion failure.
---
libavcodec/pnmdec.c | 4 ++++
1 file changed, 4 insertions(+)
diff --git a/libavcodec/pnmdec.c b/libavcodec/pnmdec.c
index ca97cc3..8961310 100644
--- a/libavcodec/pnmdec.c
+++ b/libavcodec/pnmdec.c
@@ -145,6 +145,10 @@ static int pnm_decode_frame(AVCodecContext *avctx, void *data,
/* read a sequence of digits */
do {
v = 10*v + c;
+ if (v < 0 || v > s->maxval) {
+ av_log(avctx, AV_LOG_ERROR, "value %d larger than maxval %d (or overflown)\n", v, s->maxval);
+ return AVERROR_INVALIDDATA;
+ }
c = (*s->bytestream++) - '0';
} while (c <= 9);
}
--
2.10.2
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