On Thu, May 14, 2020 at 10:02 AM Miklos Szeredi <miklos@xxxxxxxxxx> wrote:
>
> On Wed, May 13, 2020 at 12:04 PM Christoph Hellwig <hch@xxxxxxxxxxxxx> wrote:
> >
> > Needs a Cc to linux-api and linux-man.
> >
> > On Tue, May 05, 2020 at 11:59:08AM +0200, Miklos Szeredi wrote:
> > > This allows xattr ops on symlink/special files referenced by an O_PATH
> > > descriptor without having to play games with /proc/self/fd/NN (which
> > > doesn't work for symlinks anyway).
> >
> > Do we even intent to support xattrs on say links? They never wire up
> > ->listxattr and would only get them through s_xattr. I'm defintively
> > worried that this could break things without a very careful audit.
>
> Why do you think listxattr is not wired up for symlinks?
>
> Xfs and ext4 definitely do have it, and it seems most others too:
>
> $ git grep -A10 "struct inode_operations.*symlink" | grep listxattr | wc -l
> 29
In any case, I'm dropping this patch for now. The comment about
/proc/self/fd/NN not working is actually wrong; it does work despite
the target being a symlink: LOOKUP_FOLLOW only follows the magic
symlink in this case, not the symlink that is the target. So it's
possible to get (set, remove, list) the xattr on an O_PATH descriptor
using
sprintf("/proc/self/fd/%i", procpath, sizeof(procpath));
getxattr(procpath, ...);
Thanks,
Miklos
