Re: [PATCH 2/6] audit: Fix possible spurious -ENOSPC error

Jan Kara
2018-07-03T14:18:49Z

Hi Dan!

On Mon 02-07-18 09:05:49, Dan Carpenter wrote:
> url: https://github.com/0day-ci/linux/commits/Jan-Kara/audit-Fix-various-races-when-tagging-and-untagging-mounts/20180629-043337
>
> smatch warnings:
> kernel/audit_tree.c:484 tag_chunk() warn: inconsistent returns 'mutex:&audit_tree_group->mark_mutex'.
> Locked on: line 400
> Unlocked on: line 411
>
> # https://github.com/0day-ci/linux/commit/86c9c9a738e409c85891519c17d94043b7f434d5
> git remote add linux-review https://github.com/0day-ci/linux
> git remote update linux-review
> git checkout 86c9c9a738e409c85891519c17d94043b7f434d5
> vim +484 kernel/audit_tree.c
>
> 74c3cbe33 Al Viro 2007-07-22 386
> 74c3cbe33 Al Viro 2007-07-22 387 /* the first tagged inode becomes root of tree */
> 74c3cbe33 Al Viro 2007-07-22 388 static int tag_chunk(struct inode *inode, struct audit_tree *tree)
> 74c3cbe33 Al Viro 2007-07-22 389 {
> e61ce8673 Eric Paris 2009-12-17 390 struct fsnotify_mark *old_entry, *chunk_entry;
> 74c3cbe33 Al Viro 2007-07-22 391 struct audit_tree *owner;
> 74c3cbe33 Al Viro 2007-07-22 392 struct audit_chunk *chunk, *old;
> 74c3cbe33 Al Viro 2007-07-22 393 struct node *p;
> 74c3cbe33 Al Viro 2007-07-22 394 int n;
> 74c3cbe33 Al Viro 2007-07-22 395
> 86c9c9a73 Jan Kara 2018-06-28 396 mutex_lock(&audit_tree_group->mark_mutex);
> b1362edfe Jan Kara 2016-12-21 397 old_entry = fsnotify_find_mark(&inode->i_fsnotify_marks,
> b1362edfe Jan Kara 2016-12-21 398 audit_tree_group);
> 28a3a7eb3 Eric Paris 2009-12-17 399 if (!old_entry)
> 74c3cbe33 Al Viro 2007-07-22 400 return create_chunk(inode, tree);
> ^^^^^^^^^^^^^^^^^^^^^^^^^
> Should we drop the lock before this return?

No, because create_chunk() drops &audit_tree_group->mark_mutex in all the
cases. It's a bit ugly to have a function entered with mutex held and
release it but in this case it's somewhat difficult to avoid...

Honza
--
Jan Kara <jack@suse.com>
SUSE Labs, CR