On Wed, Oct 16, 2024 at 06:09:08AM +0100, Al Viro wrote:
> On Tue, Oct 15, 2024 at 04:05:15PM +0200, Christian Brauner wrote:
> > Looks good.
> >
> > Fyi, I'm using your #base.getname as a base for some other work that I'm
> > currently doing. So please don't rebase #base.getname anymore. ;)
> >
> > Since you have your #work.xattr and #work.stat using it as base it seems
> > pretty unlikely anyway but I just thought I mention explicitly that I'm
> > relying on that #base.getname branch.
>
> FWIW, I see a problem with that sucker. The trouble is in the
> combination AT_FDCWD, "", AT_EMPTY_PATH. vfs_empty_path() returns
Yeah, we're aware.
> false on that, so fstatat() in mainline falls back to vfs_statx() and
> does the right thing. This variant does _not_.
>
> Note that your variant of xattr series also ended up failing on e.g.
> getxattrat() with such combination:
> if (at_flags & AT_EMPTY_PATH && vfs_empty_path(dfd, pathname)) {
> CLASS(fd, f)(dfd);
> if (!f.file)
> return -EBADF;
> audit_file(f.file);
> return getxattr(file_mnt_idmap(f.file), file_dentry(f.file),
> name, value, size);
> }
>
> lookup_flags = (at_flags & AT_SYMLINK_NOFOLLOW) ? 0 : LOOKUP_FOLLOW;
>
> retry:
> error = user_path_at(dfd, pathname, lookup_flags, &path);
>
> ended up calling user_path_at() with empty pathname and nothing like LOOKUP_EMPTY
> in lookup_flags. Which bails out with -ENOENT, since getname() in there does
> so. My variant bails out with -EBADF and I'd argue that neither is correct.
>
> Not sure what's the sane solution here, need to think for a while...
Fwiw, in the other thread we concluded to just not care about AT_FDCWD with "".
And so far I agree with that.
