Re: [PATCH] smb: cached_dir.c: fix race in cfid release

[Henrique Carvalho <henrique.carvalho@suse.com>]

On Fri, May 02, 2025 at 04:58:00PM -0300, Enzo Matsumiya wrote:
> On 05/02, Steve French wrote:
> > I fixed a minor checkpatch warning but also noticed this compile
> > warning - is there a missing lock call?
> > 
> > cached_dir.c:429:20: warning: context imbalance in 'cfid_release' -
> > unexpected unlock
> 
> The lock is taken (inside kref_put_lock) if count == 0 (i.e. when the
> release function is called) and must be released from within the
> release function (which is done here).
> 
> However, sparse can't recognize this and also there doesn't seem to
> exist an annotation to indicate so.
> 
> @Henrique do you think you could rework the patch to something like:
> 
> cfid_release() {
> 	list_del();
> 	on_list = false;
> 	num_entries--;
> }
> 
> cfid_put() {
> 	lock();
> 	if (kref_put(..., cfid_release)) {
> 		unlock();
> 		dput();
> 		SMB2_close();
> 		free_cached_dir();
> 		return;
> 	}
> 	unlock();
> }
>

@Enzo, good idea. I will rework the patch.

Henrique