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

On Tue, May 02, 2023 at 11:08:23PM +0200, Mateusz Guzik wrote:
> On 5/2/23, Mateusz Guzik <mjguzik@gmail.com> wrote:
> > right, this should do it
> >
> > diff --git a/sys/kern/vfs_cache.c b/sys/kern/vfs_cache.c
> > index e4977392349f..b583eed5e249 100644
> > --- a/sys/kern/vfs_cache.c
> > +++ b/sys/kern/vfs_cache.c
> > @@ -4435,6 +4435,7 @@ cache_fplookup_dirfd(struct cache_fpl *fpl,
> > struct vnode **vpp)
> >         if ((*vpp)->v_type != VDIR) {
> >                 if (!((cnp->cn_flags & EMPTYPATH) != 0 &&
> > cnp->cn_pnbuf[0] == '\0')) {
> >                         cache_fpl_smr_exit(fpl);
> > +                       ndp->ni_resflags |= NIRES_EMPTYPATH;
> >                         return (cache_fpl_handled_error(fpl, ENOTDIR));
> >                 }
> >         }
> >
> 
> on another look it already works fine as is, I miseed the ! in the condition ;)

ugh, thanks, looks like it's time for me to sleep it off ))



> 
> #include <sys/stat.h>
> #include <fcntl.h>
> 
> int
> main(void)
> {
>         struct stat sb;
>         int fd;
> 
>         fd = open("/etc/fstab", O_RDONLY);
> 
>         fstatat(fd, "", &sb, AT_EMPTY_PATH);
> }
> 
> openat(AT_FDCWD,"/etc/fstab",O_RDONLY,00)        = 3 (0x3)
> fstatat(3,"",{ mode=-rw-r--r-- ,inode=370100,size=145,blksize=4096
> },AT_EMPTY_PATH) = 0 (0x0)
> 
> dtrace -n 'vfs:fplookup:: /execname == "a.out"/ { @[stack(), arg1,
> arg2] = count(); }'
> [snip]
>               kernel`kern_statat+0xec
>               kernel`sys_fstatat+0x27
>               kernel`amd64_syscall+0x109
>               kernel`0xffffffff809726bb
>              4980                3                1
> 
> as in handled in cache_fplookup_emptypath
> 
> >
> > On 5/2/23, Dmitry Chagin <dchagin@freebsd.org> wrote:
> >> 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);
> >>> >
> >>
> >
> >
> > --
> > Mateusz Guzik <mjguzik gmail.com>
> >
> 
> 
> -- 
> Mateusz Guzik <mjguzik gmail.com>