On Fri, Dec 18, 2015 at 08:13:06PM +0100, Andreas Cadhalpun wrote:
> On 18.12.2015 20:08, Luca Barbato wrote:
> > On 18/12/15 20:04, Andreas Cadhalpun wrote:
> >> This is used to check if the input buffer is larger enough, so if this
> >> overflows it can cause a false negative leading to a segmentation fault
> >> in bytestream2_get_bufferu.
> >>
> >> Signed-off-by: Andreas Cadhalpun <andreas.cadhal...@googlemail.com>
> >> ---
> >> libavcodec/xwddec.c | 6 ++++++
> >> 1 file changed, 6 insertions(+)
> >>
> >> diff --git a/libavcodec/xwddec.c b/libavcodec/xwddec.c
> >> index 2febedc..311eeec 100644
> >> --- a/libavcodec/xwddec.c
> >> +++ b/libavcodec/xwddec.c
> >> @@ -127,6 +127,12 @@ static int xwd_decode_frame(AVCodecContext *avctx,
> >> void *data,
> >> return AVERROR_INVALIDDATA;
> >> }
> >>
> >> + if (lsize > UINT_MAX / avctx->height) {
> >> + av_log(avctx, AV_LOG_ERROR, "lsize %u too large for height %d\n",
> >> + lsize, avctx->height);
> >> + return AVERROR_INVALIDDATA;
> >> + }
> >> +
> >> if (ncolors > 256) {
> >> av_log(avctx, AV_LOG_ERROR, "invalid number of entries in
> >> colormap\n");
> >> return AVERROR_INVALIDDATA;
> >>
> >
> > Should go after the av_image_check_size or you'd have a division by 0.
>
> Indeed. Updated patch attached.
>
> Best regards,
> Andreas
> > xwddec.c | 6 ++++++ > 1 file changed, 6 insertions(+) > 0be27d89a669445b523bfdac99884065e3581f3c > 0001-xwddec-prevent-overflow-of-lsize-avctx-height.patch > From fb40616d7b432680b92dc3adc44a5b5d12fac55d Mon Sep 17 00:00:00 2001 > From: Andreas Cadhalpun <andreas.cadhal...@googlemail.com> > Date: Fri, 18 Dec 2015 19:28:51 +0100 > Subject: [PATCH] xwddec: prevent overflow of lsize * avctx->height > > This is used to check if the input buffer is larger enough, so if this > overflows it can cause a false negative leading to a segmentation fault > in bytestream2_get_bufferu. cant the addition overflow too in the input buffer check ? if so then using 64bit in the input buffer check would avoid the need for a explicit check on lsize [...] -- Michael GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB Complexity theory is the science of finding the exact solution to an approximation. Benchmarking OTOH is finding an approximation of the exact
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