[FFmpeg-devel] [PATCH] avformat/vividas: Use signed n in read_sb_block()

[Michael Niedermayer]

On Wed, Feb 24, 2021 at 03:23:40PM +0100, Anton Khirnov wrote:
> Quoting Michael Niedermayer (2021-02-15 21:31:23)
> > Fixes: OOM
> > Fixes: 27780/clusterfuzz-testcase-minimized-ffmpeg_dem_VIVIDAS_fuzzer-5097985075314688
> > 
> > Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
> > Signed-off-by: Michael Niedermayer <michael at niedermayer.cc>
> > ---
> >  libavformat/vividas.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/libavformat/vividas.c b/libavformat/vividas.c
> > index d745770dc4..b172a48b29 100644
> > --- a/libavformat/vividas.c
> > +++ b/libavformat/vividas.c
> > @@ -235,7 +235,7 @@ static uint8_t *read_sb_block(AVIOContext *src, unsigned *size,
> >      uint8_t *buf;
> >      uint8_t ibuf[8], sbuf[8];
> >      uint32_t k2;
> > -    unsigned n;
> > +    int n;
> >  
> 
> Why would that be better, when it's assigned a uint32_t?

one (maybe not the only one) issue is
if (avio_read(src, buf+8, n) < n) {

avio_read() returns int and has a int size
so this will not work at all with a unsigned int, not only will it not read
more than INT_MAX it also when it fails with an error fail to treat it as 
an error

do you prefer a diferent solution ?

thx

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