On Thu 22-12-16 18:18:36, Paul Moore wrote: > On Thu, Dec 22, 2016 at 4:15 AM, Jan Kara <jack(a)suse.cz&gt; wrote: > > Audit tree code was happily adding new notification marks while holding > > spinlocks. Since fsnotify_add_mark() acquires group->mark_mutex this can > > lead to sleeping while holding a spinlock, deadlocks due to lock > > inversion, and probably other fun. Fix the problem by acquiring > > group->mark_mutex earlier. > > > > CC: Paul Moore <paul(a)paul-moore.com&gt; > > Signed-off-by: Jan Kara <jack(a)suse.cz&gt; > > --- > > kernel/audit_tree.c | 13 +++++++++++-- > > 1 file changed, 11 insertions(+), 2 deletions(-) > > [SIDE NOTE: this patch explains your comments and my earlier concern > about the locked/unlocked variants of fsnotify_add_mark() in > untag_chunk()] > > Ouch. Thanks for catching this ... what is your goal with these > patches, are you targeting this as a fix during the v4.10-rcX cycle? > If not, any objections if I pull this patch into the audit tree and > send this to Linus during the v4.10-rcX cycle (assuming it passes > testing, yadda yadda)? Sure, go ahead. I plan these patches for the next merge window. So I can rebase the series once you merge audit fixes...

> > diff --git a/kernel/audit_tree.c b/kernel/audit_tree.c > > index f3130eb0a4bd..156b6a93f4fc 100644 > > --- a/kernel/audit_tree.c > > +++ b/kernel/audit_tree.c > > @@ -231,6 +231,7 @@ static void untag_chunk(struct node *p) > > if (size) > > new = alloc_chunk(size); > > > > + mutex_lock(&entry->group->mark_mutex); > > spin_lock(&entry->lock); > > if (chunk->dead || !entry->inode) { > > spin_unlock(&entry->lock); > > @@ -258,7 +259,8 @@ static void untag_chunk(struct node *p) > > if (!new) > > goto Fallback; > > > > - if (fsnotify_add_mark(&new->mark, entry->group, entry->inode, NULL, 1)) { > > + if (fsnotify_add_mark_locked(&new->mark, entry->group, entry->inode, > > + NULL, 1)) { > > fsnotify_put_mark(&new->mark); > > goto Fallback; > > } > > @@ -309,6 +311,7 @@ static void untag_chunk(struct node *p) > > spin_unlock(&hash_lock); > > spin_unlock(&entry->lock); > > out: > > + mutex_unlock(&entry->group->mark_mutex); > > fsnotify_put_mark(entry); > > spin_lock(&hash_lock); > > } > > @@ -385,17 +388,21 @@ static int tag_chunk(struct inode *inode, struct audit_tree *tree) > > > > chunk_entry = &chunk->mark; > > > > + mutex_lock(&old_entry->group->mark_mutex); > > spin_lock(&old_entry->lock); > > if (!old_entry->inode) { > > /* old_entry is being shot, lets just lie */ > > spin_unlock(&old_entry->lock); > > + mutex_unlock(&old_entry->group->mark_mutex); > > fsnotify_put_mark(old_entry); > > free_chunk(chunk); > > return -ENOENT; > > } > > > > - if (fsnotify_add_mark(chunk_entry, old_entry->group, old_entry->inode, NULL, 1)) { > > + if (fsnotify_add_mark_locked(chunk_entry, old_entry->group, > > + old_entry->inode, NULL, 1)) { > > spin_unlock(&old_entry->lock); > > + mutex_unlock(&old_entry->group->mark_mutex); > > fsnotify_put_mark(chunk_entry); > > fsnotify_put_mark(old_entry); > > return -ENOSPC; > > @@ -411,6 +418,7 @@ static int tag_chunk(struct inode *inode, struct audit_tree *tree) > > chunk->dead = 1; > > spin_unlock(&chunk_entry->lock); > > spin_unlock(&old_entry->lock); > > + mutex_unlock(&old_entry->group->mark_mutex); > > > > fsnotify_destroy_mark(chunk_entry, audit_tree_group); > > > > @@ -443,6 +451,7 @@ static int tag_chunk(struct inode *inode, struct audit_tree *tree) > > spin_unlock(&hash_lock); > > spin_unlock(&chunk_entry->lock); > > spin_unlock(&old_entry->lock); > > + mutex_unlock(&old_entry->group->mark_mutex); > > fsnotify_destroy_mark(old_entry, audit_tree_group); > > fsnotify_put_mark(chunk_entry); /* drop initial reference */ > > fsnotify_put_mark(old_entry); /* pair to fsnotify_find mark_entry */ > > -- > > 2.10.2 > >