[PATCH AUTOSEL 5.4 1/4] epoll: do not insert into poll queues until all sanity checks are done

[PATCH AUTOSEL 5.4 1/4] epoll: do not insert into poll queues until all sanity checks are done

[Sasha Levin]

From: Al Viro <viro@zeniv.linux.org.uk>

[ Upstream commit f8d4f44df056c5b504b0d49683fb7279218fd207 ]

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 fs/eventpoll.c | 37 ++++++++++++++++++-------------------
 1 file changed, 18 insertions(+), 19 deletions(-)

diff --git a/fs/eventpoll.c b/fs/eventpoll.c
index ae1d32344f7ac..f70df53666ed1 100644
--- a/fs/eventpoll.c
+++ b/fs/eventpoll.c
@@ -1527,6 +1527,22 @@ static int ep_insert(struct eventpoll *ep, const struct epoll_event *event,
 		RCU_INIT_POINTER(epi->ws, NULL);
 	}
 
+	/* Add the current item to the list of active epoll hook for this file */
+	spin_lock(&tfile->f_lock);
+	list_add_tail_rcu(&epi->fllink, &tfile->f_ep_links);
+	spin_unlock(&tfile->f_lock);
+
+	/*
+	 * Add the current item to the RB tree. All RB tree operations are
+	 * protected by "mtx", and ep_insert() is called with "mtx" held.
+	 */
+	ep_rbtree_insert(ep, epi);
+
+	/* now check if we've created too many backpaths */
+	error = -EINVAL;
+	if (full_check && reverse_path_check())
+		goto error_remove_epi;
+
 	/* Initialize the poll table using the queue callback */
 	epq.epi = epi;
 	init_poll_funcptr(&epq.pt, ep_ptable_queue_proc);
@@ -1549,22 +1565,6 @@ static int ep_insert(struct eventpoll *ep, const struct epoll_event *event,
 	if (epi->nwait < 0)
 		goto error_unregister;
 
-	/* Add the current item to the list of active epoll hook for this file */
-	spin_lock(&tfile->f_lock);
-	list_add_tail_rcu(&epi->fllink, &tfile->f_ep_links);
-	spin_unlock(&tfile->f_lock);
-
-	/*
-	 * Add the current item to the RB tree. All RB tree operations are
-	 * protected by "mtx", and ep_insert() is called with "mtx" held.
-	 */
-	ep_rbtree_insert(ep, epi);
-
-	/* now check if we've created too many backpaths */
-	error = -EINVAL;
-	if (full_check && reverse_path_check())
-		goto error_remove_epi;
-
 	/* We have to drop the new item inside our item list to keep track of it */
 	write_lock_irq(&ep->lock);
 
@@ -1593,6 +1593,8 @@ static int ep_insert(struct eventpoll *ep, const struct epoll_event *event,
 
 	return 0;
 
+error_unregister:
+	ep_unregister_pollwait(ep, epi);
 error_remove_epi:
 	spin_lock(&tfile->f_lock);
 	list_del_rcu(&epi->fllink);
@@ -1600,9 +1602,6 @@ static int ep_insert(struct eventpoll *ep, const struct epoll_event *event,
 
 	rb_erase_cached(&epi->rbn, &ep->rbr);
 
-error_unregister:
-	ep_unregister_pollwait(ep, epi);
-
 	/*
 	 * We need to do this because an event could have been arrived on some
 	 * allocated wait queue. Note that we don't care about the ep->ovflist
-- 
2.25.1

[PATCH AUTOSEL 5.4 3/4] ep_create_wakeup_source(): dentry name can change under you...

[Sasha Levin]

From: Al Viro <viro@zeniv.linux.org.uk>

[ Upstream commit 3701cb59d892b88d569427586f01491552f377b1 ]

or get freed, for that matter, if it's a long (separately stored)
name.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 fs/eventpoll.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/fs/eventpoll.c b/fs/eventpoll.c
index f70df53666ed1..1c9f1486e5cf9 100644
--- a/fs/eventpoll.c
+++ b/fs/eventpoll.c
@@ -1455,7 +1455,7 @@ static int reverse_path_check(void)
 
 static int ep_create_wakeup_source(struct epitem *epi)
 {
-	const char *name;
+	struct name_snapshot n;
 	struct wakeup_source *ws;
 
 	if (!epi->ep->ws) {
@@ -1464,8 +1464,9 @@ static int ep_create_wakeup_source(struct epitem *epi)
 			return -ENOMEM;
 	}
 
-	name = epi->ffd.file->f_path.dentry->d_name.name;
-	ws = wakeup_source_register(NULL, name);
+	take_dentry_name_snapshot(&n, epi->ffd.file->f_path.dentry);
+	ws = wakeup_source_register(NULL, n.name.name);
+	release_dentry_name_snapshot(&n);
 
 	if (!ws)
 		return -ENOMEM;
-- 
2.25.1