Re: [PATCH i-g-t rfc 01/29] lib/igt_debugfs: Prevent buffer overflow

["Lankhorst, Maarten" <maarten.lankhorst@intel.com>]

Robert Foss schreef op do 12-01-2017 om 11:30 [-0500]:
> 
> On 2017-01-12 04:14 AM, Lankhorst, Maarten wrote:
> > 
> > Robert Foss schreef op wo 11-01-2017 om 15:41 [-0500]:
> > > 
> > > buf array may overflow with when writing '\0' if
> > > MAX_LINE_LEN bytes are read during read().
> > How?
> > 
> > char buf[MAX_LINE_LEN + 1];
> 
> I actually missed the + 1, but parts of the commit are still
> relevant 
> though, as the errno at least in theory could be != EAGAIN.
> 
> So I'd like to keep the below check, to prevent compiler warnings.
> if (bytes_read < 0)
> 
> Sounds ok?
Yes. :)
> 
> Rob.
> > 
> > 
> > > 
> > > Signed-off-by: Robert Foss <robert.foss@collabora.com>
> > > ---
> > >  lib/igt_debugfs.c | 8 +++++---
> > >  1 file changed, 5 insertions(+), 3 deletions(-)
> > > 
> > > diff --git a/lib/igt_debugfs.c b/lib/igt_debugfs.c
> > > index d828687a..8b8a627a 100644
> > > --- a/lib/igt_debugfs.c
> > > +++ b/lib/igt_debugfs.c
> > > @@ -594,13 +594,15 @@ static int read_crc(igt_pipe_crc_t
> > > *pipe_crc,
> > > igt_crc_t *out)
> > >  		read_len = MAX_LINE_LEN;
> > > 
> > >  	igt_set_timeout(5, "CRC reading");
> > > -	bytes_read = read(pipe_crc->crc_fd, &buf, read_len);
> > > +	bytes_read = read(pipe_crc->crc_fd, &buf, read_len - 1);
> > >  	igt_reset_timeout();
> > > 
> > > -	if (bytes_read < 0 && errno == EAGAIN) {
> > > +	if (bytes_read < 0 && errno == EAGAIN)
> > >  		igt_assert(pipe_crc->flags & O_NONBLOCK);
> > > +
> > > +	if (bytes_read < 0)
> > >  		bytes_read = 0;
> > > -	}
> > > +
> > >  	buf[bytes_read] = '\0';
> > > 
> > >  	if (bytes_read && !pipe_crc_init_from_string(pipe_crc,
> > > out,
> > > buf))
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