Re: [RFC] vfs: skip extra attributes check on removal for symlinks

[Al Viro]

On Thu, May 10, 2018 at 11:05:51PM +0000, Luis R. Rodriguez wrote:
> On Thu, May 10, 2018 at 09:48:07PM +0100, Al Viro wrote:
> > On Thu, Apr 26, 2018 at 04:46:39PM -0700, Luis R. Rodriguez wrote:
> > 
> > > Since we cannot set these attributes we should special-case the
> > > immutable/append on delete for symlinks, this would be consistent with
> > > what we *do* allow on Linux for all filesystems.
> > 
> > Er...  So why not simply sanity-check it in places that set it on
> > inodes? 
> 
> The patch is not about sanity-checks on setters though as *that* is in place
> already. Its about the case where the filesystem gets corrupted and the VFS
> *still* does process these attributes for symlinks and still prevents
> deletion because of these attributes.

... and this corrupted fs ends up setting those flags on in-core inodes.
Which is where we ought to block that.  Seriously, let's make sure that
->i_flags manipulations are done by inode_set_flags() (e.g. btrfs open-codes
that, apparently) and let's make _that_ check and reject those.