Re: [PATCH v6 3/8] vfio: selftests: Introduce a sysfs lib

[Raghavendra Rao Ananta]

On Wed, Mar 4, 2026 at 2:53 PM David Matlack <dmatlack@xxxxxxxxxx> wrote:
>
> On 2026-03-03 07:38 PM, Raghavendra Rao Ananta wrote:
>
> > +     ret = readlink(path, vf_path, PATH_MAX);
> > +     VFIO_ASSERT_NE(ret, -1);
> > +     vf_path[ret] = '\0';
>
> ...
>
> > +     ret = readlink(path, dev_iommu_group_path, sizeof(dev_iommu_group_path));
> > +     VFIO_ASSERT_NE(ret, -1, "Failed to get the IOMMU group for device: %s\n", bdf);
> > +     dev_iommu_group_path[ret] = '\0';
>
> ...
>
> > +     ret = readlink(path, driver_path, PATH_MAX);
> > +     if (ret == -1) {
> > +             free(out_driver);
> > +
> > +             if (errno == ENOENT)
> > +                     return NULL;
> > +
> > +             VFIO_FAIL("Failed to read %s\n", path);
> > +     }
> > +     driver_path[ret] = '\0';
>
> These can all write off the end of the buffer if ret == PATH_MAX.
>
> Also there is an inconsistency in these calls. 2 use hard-coded PATH_MAX
> while the other uses sizeof().
>
> Perhaps add a wrapper to handle all the details?
>
> #define readlink_safe(path, buf) ({                           \
>         int __ret = readlink(_path, _buf, sizeof(_buf) - 1);  \
>         if (__ret != -1)                                      \
>                 _buf[__ret] = 0;                              \
>         __ret;
> })

Yeah, good idea. I'll consider this in v7.

Thank you.
Raghavendra