From: Siddh Raman Pant <code@siddh.me>
To: David Howells <dhowells@redhat.com>,
Christophe JAILLET <christophe.jaillet@wanadoo.fr>,
Eric Dumazet <edumazet@google.com>,
"Fabio M. De Francesco" <fmdefrancesco@gmail.com>
Cc: linux-security-modules <linux-security-module@vger.kernel.org>,
linux-kernel <linux-kernel@vger.kernel.org>,
linux-kernel-mentees
<linux-kernel-mentees@lists.linuxfoundation.org>,
syzbot+c70d87ac1d001f29a058@syzkaller.appspotmail.com
Subject: [PATCH v2] kernel/watch_queue: Make pipe NULL while clearing watch_queue
Date: Sun, 24 Jul 2022 09:32:40 +0530 [thread overview]
Message-ID: <20220724040240.7842-1-code@siddh.me> (raw)
If not done, a reference to a freed pipe remains in the watch_queue,
as this function is called before freeing a pipe in free_pipe_info()
(see line 834 of fs/pipe.c).
This causes a UAF when post_one_notification tries to access the pipe on
a key update, which is reported by syzbot.
Bug report: https://syzkaller.appspot.com/bug?id=1870dd7791ba05f2ea7f47f7cbdde701173973fc
Reported-and-tested-by: syzbot+c70d87ac1d001f29a058@syzkaller.appspotmail.com
Signed-off-by: Siddh Raman Pant <code@siddh.me>
---
Changes since v1:
- Removed the superfluous ifdef guard.
kernel/watch_queue.c | 9 ++++++++-
1 file changed, 8 insertions(+), 1 deletion(-)
diff --git a/kernel/watch_queue.c b/kernel/watch_queue.c
index bb9962b33f95..0357e5c6cf18 100644
--- a/kernel/watch_queue.c
+++ b/kernel/watch_queue.c
@@ -637,8 +637,15 @@ void watch_queue_clear(struct watch_queue *wqueue)
spin_lock_bh(&wqueue->lock);
}
- spin_unlock_bh(&wqueue->lock);
rcu_read_unlock();
+
+ /* Clearing the watch queue, so we should clean the associated pipe. */
+ if (wqueue->pipe) {
+ wqueue->pipe->watch_queue = NULL;
+ wqueue->pipe = NULL;
+ }
+
+ spin_unlock_bh(&wqueue->lock);
}
/**
--
2.35.1
next reply other threads:[~2022-07-24 4:03 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-07-24 4:02 Siddh Raman Pant [this message]
[not found] <20220724052426.2504-1-hdanton@sina.com>
2022-07-24 6:26 ` [PATCH v2] kernel/watch_queue: Make pipe NULL while clearing watch_queue Siddh Raman Pant
[not found] ` <20220724071958.2557-1-hdanton@sina.com>
2022-07-24 7:48 ` Siddh Raman Pant
2022-07-27 14:49 ` David Howells
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