Re: [PATCH] util/vfio-helpers: Use g_file_read_link()

["Daniel P. Berrangé" <berrange@redhat.com>]

On Mon, May 22, 2023 at 02:38:44PM +0200, Philippe Mathieu-Daudé wrote:
> On 22/5/23 13:49, Akihiko Odaki wrote:
> > When _FORTIFY_SOURCE=2, glibc version is 2.35, and GCC version is
> > 12.1.0, the compiler complains as follows:
> > 
> > In file included from /usr/include/features.h:490,
> >                   from /usr/include/bits/libc-header-start.h:33,
> >                   from /usr/include/stdint.h:26,
> >                   from /usr/lib/gcc/aarch64-unknown-linux-gnu/12.1.0/include/stdint.h:9,
> >                   from /home/alarm/q/var/qemu/include/qemu/osdep.h:94,
> >                   from ../util/vfio-helpers.c:13:
> > In function 'readlink',
> >      inlined from 'sysfs_find_group_file' at ../util/vfio-helpers.c:116:9,
> >      inlined from 'qemu_vfio_init_pci' at ../util/vfio-helpers.c:326:18,
> >      inlined from 'qemu_vfio_open_pci' at ../util/vfio-helpers.c:517:9:
> > /usr/include/bits/unistd.h:119:10: error: argument 2 is null but the corresponding size argument 3 value is 4095 [-Werror=nonnull]
> >    119 |   return __glibc_fortify (readlink, __len, sizeof (char),
> >        |          ^~~~~~~~~~~~~~~
> > 
> > This error implies the allocated buffer can be NULL. Use
> > g_file_read_link(), which allocates buffer automatically to avoid the
> > error.
> > 
> > Signed-off-by: Akihiko Odaki <akihiko.odaki@daynix.com>
> > ---
> >   util/vfio-helpers.c | 8 +++++---
> >   1 file changed, 5 insertions(+), 3 deletions(-)
> > 
> > diff --git a/util/vfio-helpers.c b/util/vfio-helpers.c
> > index 2d8af38f88..e482ab22e2 100644
> > --- a/util/vfio-helpers.c
> > +++ b/util/vfio-helpers.c
> > @@ -106,15 +106,17 @@ struct QEMUVFIOState {
> >    */
> >   static char *sysfs_find_group_file(const char *device, Error **errp)
> >   {
> > +    g_autoptr(GError) gerr;
> 
> Shouldn't this also be NULL-initialized (other picky compilers)?

Yes, *all* use of g_auto* must have an initializer at time of
declaration.

With regards,
Daniel
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