Re: [PATCH 3/6] audit: Fix possible tagging failures

On Tue, Jul 3, 2018 at 5:21 PM, Jan Kara <jack(a)suse.cz&gt; wrote: > On Fri 29-06-18 15:05:07, Amir Goldstein wrote: >> On Thu, Jun 28, 2018 at 7:40 PM, Jan Kara <jack(a)suse.cz&gt; wrote: >> > Audit tree code is replacing marks attached to inodes in non-atomic way. >> > Thus fsnotify_find_mark() in tag_chunk() may find a mark that belongs to >> > a chunk that is no longer valid one and will soon be destroyed. Tags >> > added to such chunk will be simply lost. >> > >> > Fix the problem by making sure old mark is marked as going away (through >> > fsnotify_detach_mark()) before dropping mark_mutex and thus in an atomic >> > way wrt tag_chunk(). Note that this does not fix the problem completely >> > as if tag_chunk() finds a mark that is going away, it fails with >> > -ENOENT. But at least the failure is not silent and currently there's no >> > way to search for another fsnotify mark attached to the inode. We'll fix >> > this problem in later patch. >> > >> > Signed-off-by: Jan Kara <jack(a)suse.cz&gt; >> > --- >> >> This one too looks sane. >> Without knowing anything about audit_watch, there seems to be >> an fsnotify_destroy_mark() after unlock of audit_filter_mutex, so it >> may require a similar fix. > > Where? I don't see any call to fsnotify_destroy_mark() left after this > patch... > Not directly related to this cleanup, but looking in other audit modules, fsnotify_destroy_mark() in audit_remove_parent_watches() is called outside audit_filter_mutex and audit_find_parent() in audit_add_watch() is called inside audit_filter_mutex, so I was wondering if there was a similar race window in that code. I didn't spend enough time looking at audit_watch.c to understand what is going on in there.