From: Benjamin Segall <bsegall@google.com>
Date: Tue, 30 May 2023 18:32:28 +0000 (-0700)
Subject: epoll: ep_autoremove_wake_function should use list_del_init_careful
X-Git-Tag: v6.3.9~141
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=7d9792a8abccfe7392f6b1f13f3b374f698c75fe;p=thirdparty%2Fkernel%2Fstable.git

epoll: ep_autoremove_wake_function should use list_del_init_careful

commit 2192bba03d80f829233bfa34506b428f71e531e7 upstream.

autoremove_wake_function uses list_del_init_careful, so should epoll's
more aggressive variant.  It only doesn't because it was copied from an
older wait.c rather than the most recent.

[bsegall@google.com: add comment]
  Link: https://lkml.kernel.org/r/xm26bki0ulsr.fsf_-_@google.com
Link: https://lkml.kernel.org/r/xm26pm6hvfer.fsf@google.com
Fixes: a16ceb139610 ("epoll: autoremove wakers even more aggressively")
Signed-off-by: Ben Segall <bsegall@google.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Christian Brauner <brauner@kernel.org>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---

diff --git a/fs/eventpoll.c b/fs/eventpoll.c
index 64659b1109733..eccecd3fac90c 100644
--- a/fs/eventpoll.c
+++ b/fs/eventpoll.c
@@ -1760,7 +1760,11 @@ static int ep_autoremove_wake_function(struct wait_queue_entry *wq_entry,
 {
 	int ret = default_wake_function(wq_entry, mode, sync, key);
 
-	list_del_init(&wq_entry->entry);
+	/*
+	 * Pairs with list_empty_careful in ep_poll, and ensures future loop
+	 * iterations see the cause of this wakeup.
+	 */
+	list_del_init_careful(&wq_entry->entry);
 	return ret;
 }