Hi Laurent,
On Fri, Feb 22, 2019 at 01:47:39PM +0200, Laurent Pinchart wrote:
> Hi Sakari,
>
> On Wed, Feb 20, 2019 at 11:26:52PM +0200, Sakari Ailus wrote:
> > On Wed, Feb 20, 2019 at 02:51:22PM +0200, Laurent Pinchart wrote:
> > > Signed-off-by: Laurent Pinchart <laurent.pinchart@xxxxxxxxxxxxxxxx>
> > > ---
> > > yavta.c | 25 +++++++++++++++++++++++++
> > > 1 file changed, 25 insertions(+)
> > >
> > > diff --git a/yavta.c b/yavta.c
> > > index 1490878c6f7e..2d49131a4271 100644
> > > --- a/yavta.c
> > > +++ b/yavta.c
> > > @@ -1334,6 +1334,31 @@ static int video_parse_control_array(const struct v4l2_query_ext_ctrl *query,
> > > __u32 value;
> > >
> > > for ( ; isspace(*val); ++val) { };
> > > +
> > > + if (*val == '<') {
> > > + /* Read the control value from the given file. */
> > > + ssize_t size;
> > > + int fd;
> > > +
> > > + val++;
> > > + fd = open(val, O_RDONLY);
> > > + if (fd < 0) {
> > > + printf("unable to open control file `%s'\n", val);
> > > + return -EINVAL;
> > > + }
> > > +
> > > + size = read(fd, ctrl->ptr, ctrl->size);
> >
> > Note that a read of count reads *up to* count number of bytes from the file
> > descriptor. In other words, it's perfectly correct for it to read less than
> > requested.
> >
> > How about using fread(3) instead? Or changing this into a loop?
>
> Do you expect this to cause issues in practice ? When does read() return
> less data than requested for regular files ?
API-wise there's no guarantee. This could simply fail for someone at some
point when reading a largish compound control.
Also try reading from e.g. /dev/random. :-)
--
Sakari Ailus
