[PATCH libdrm 1/3] xf86drm: adjust device node path for minor base

[Jonathan Gray]

On Mon, Dec 12, 2016 at 02:10:31PM +0000, Emil Velikov wrote:
> On 10 December 2016 at 05:52, Jonathan Gray <jsg at jsg.id.au> wrote:
> > When constructing a path to a device node the minor number retrieved
> > from fstat needs to have the offset of the node type subtracted from it.
> > Control and render node types have the same major as the primary node
> > but each has their own block of minor types at fixed offsets.
> >
> > Signed-off-by: Jonathan Gray <jsg at jsg.id.au>
> > ---
> >  xf86drm.c | 16 ++++++++++++----
> >  1 file changed, 12 insertions(+), 4 deletions(-)
> >
> > diff --git a/xf86drm.c b/xf86drm.c
> > index 2e8c956..6705605 100644
> > --- a/xf86drm.c
> > +++ b/xf86drm.c
> > @@ -2838,7 +2838,7 @@ out_close_dir:
> >      char buf[PATH_MAX + 1];
> >      const char *dev_name;
> >      unsigned int maj, min;
> > -    int n;
> > +    int n, base;
> >
> >      if (fstat(fd, &sbuf))
> >          return NULL;
> > @@ -2863,7 +2863,11 @@ out_close_dir:
> >          return NULL;
> >      };
> >
> > -    n = snprintf(buf, sizeof(buf), dev_name, DRM_DIR_NAME, min);
> > +    base = drmGetMinorBase(type);
> > +    if (base < 0 || min < base)
> min < base seems bogus, since it will never be true, right ? If so can
> we drop it please.
> 
> Same goes below and in 2/3.
> Emil

For drmGetDevice2() and drmGetDeviceNameFromFd2() yes as it should be
caught by drmGetMinorType().

For drmGetMinorNameForFD() it would be possible for a minor number to be
wrong and have it not caught as the type comes from an argument not
inspection of the /dev node.  A sanity check of the type argument
could be made based on the minor found on disk but that ends up
being the same kind of test.