Re: [PATCH v2] attr: block mode changes of symlinks

On Wed, Jul 12, 2023 at 08:58:49PM +0200, Christian Brauner wrote:

(1) Filesystems that don't implement a i_op->setattr() for symlinks.

Such filesystems may or may not know that without i_op->setattr()
defined, notify_change() falls back to simple_setattr() causing the
inode's mode in the inode cache to be changed.

Btw, I think this fallback is pretty harmful. At some point we should probably start auditing all instances and wire the ones up that should be using simple_setattr (probably mostly just in-memory file systems) and refuse attribute changes if .setattr is NULL.