Re: [PATCH] 9pfs: local: Do not follow symlink in _nofollow

[Christian Schoenebeck <qemu_oss@crudebyte.com>]

On Mittwoch, 27. April 2022 12:21:51 CEST Greg Kurz wrote:
> On Wed, 27 Apr 2022 10:46:31 +0200
> 
> Christian Schoenebeck <qemu_oss@crudebyte.com> wrote:
> > On Mittwoch, 27. April 2022 04:45:45 CEST Akihiko Odaki wrote:
> > > Signed-off-by: Akihiko Odaki <akihiko.odaki@gmail.com>
> > > ---
> > > 
> > >  hw/9pfs/9p-local.c | 2 +-
> > >  1 file changed, 1 insertion(+), 1 deletion(-)
> > > 
> > > diff --git a/hw/9pfs/9p-local.c b/hw/9pfs/9p-local.c
> > > index d42ce6d8b82..def8afdb4d6 100644
> > > --- a/hw/9pfs/9p-local.c
> > > +++ b/hw/9pfs/9p-local.c
> > > @@ -365,7 +365,7 @@ static int fchmodat_nofollow(int dirfd, const char
> > > *name, mode_t mode) if (fd == -1) {
> > > 
> > >          /* In case the file is writable-only and isn't a directory. */
> > >          if (errno == EACCES) {
> > > 
> > > -            fd = openat_file(dirfd, name, O_WRONLY, 0);
> > > +            fd = openat_file(dirfd, name, O_WRONLY | O_NOFOLLOW, 0);
> > 
> > O_NOFOLLOW flag is always added inside openat_file() implementation:
> > 
> > https://github.com/qemu/qemu/blob/master/hw/9pfs/9p-util.h#L60
> > 
> > So this change is not necessary AFAICS.
> 
> Right, and with macOS in mind, maybe fchmodat(AT_SYMLINK_NOFOLLOW) just
> works unlike with linux ?

Yep, fchmodat(AT_SYMLINK_NOFOLLOW) seems to work on macOS! Like you already 
suggested on the other thread, it would make sense to move current 
implementation of fchmodat_nofollow() to 9p-util-linux.h/.c and let macOS just 
use fchmodat(AT_SYMLINK_NOFOLLOW) instead.

Best regards,
Christian Schoenebeck