Re: git: a1d71cebc05c - main - fstatat(2): restore AT_EMPTY_PATH handling

On Tue, May 02, 2023 at 03:04:37PM -0400, Mark Johnston wrote:
> On Tue, May 02, 2023 at 08:00:01PM +0300, Dmitry Chagin wrote:
> > On Tue, May 02, 2023 at 03:12:51PM +0000, Konstantin Belousov wrote:
> > > The branch main has been updated by kib:
> > > 
> > > URL: https://cgit.FreeBSD.org/src/commit/?id=a1d71cebc05ccfeedf95f2db3e94b17270167888
> > > 
> > > commit a1d71cebc05ccfeedf95f2db3e94b17270167888
> > > Author:     Konstantin Belousov <kib@FreeBSD.org>
> > > AuthorDate: 2023-05-02 15:11:39 +0000
> > > Commit:     Konstantin Belousov <kib@FreeBSD.org>
> > > CommitDate: 2023-05-02 15:11:39 +0000
> > > 
> > >     fstatat(2): restore AT_EMPTY_PATH handling
> > >     
> > >     Fixes:  cb858340dcbf214cc4c4d78dbb741620d7b3a252
> > >     Reported by:    markj
> > >     Sponsored by:   The FreeBSD Foundation
> > > ---
> > >  sys/kern/vfs_syscalls.c | 6 +++++-
> > >  1 file changed, 5 insertions(+), 1 deletion(-)
> > > 
> > > diff --git a/sys/kern/vfs_syscalls.c b/sys/kern/vfs_syscalls.c
> > > index 5c0a291e3b0b..d68af4ea4d51 100644
> > > --- a/sys/kern/vfs_syscalls.c
> > > +++ b/sys/kern/vfs_syscalls.c
> > > @@ -2438,8 +2438,12 @@ kern_statat(struct thread *td, int flag, int fd, const char *path,
> > >  	    AT_SYMLINK_NOFOLLOW | AT_EMPTY_PATH) | LOCKSHARED | LOCKLEAF |
> > >  	    AUDITVNODE1, pathseg, path, fd, &cap_fstat_rights);
> > >  
> > > -	if ((error = namei(&nd)) != 0)
> > > +	if ((error = namei(&nd)) != 0) {
> > > +		if (error == ENOTDIR &&
> > > +		    (nd.ni_resflags & NIRES_EMPTYPATH) != 0)
> > > +			error = kern_fstat(td, fd, sbp);
> > >  		return (error);
> > > +	}
> > 
> > cache_fplookup_dirfd() doesnt set the NIRES_EMPTYPATH flag
> 
> It doesn't, but for an AT_EMPTY_PATH lookup it aborts the lookup and
> returns ENOTDIR to namei(), which sets NIRES_EMPTYPATH before passing
> the error up.
> 

it call cache_fpl_handled_error() which is set status to
CACHE_FPL_STATUS_HADLED, namei() simply return error in that path


> > >  	error = VOP_STAT(nd.ni_vp, sbp, td->td_ucred, NOCRED);
> > >  	NDFREE_PNBUF(&nd);
> > >  	vput(nd.ni_vp);
> >