From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id B5BA3C3F6B0 for ; Mon, 1 Aug 2022 12:10:20 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233724AbiHAMKT (ORCPT ); Mon, 1 Aug 2022 08:10:19 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:56230 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233631AbiHAMJh (ORCPT ); Mon, 1 Aug 2022 08:09:37 -0400 Received: from ams.source.kernel.org (ams.source.kernel.org [145.40.68.75]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 5036F6610D; Mon, 1 Aug 2022 04:56:21 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id BCE4CB81171; Mon, 1 Aug 2022 11:56:19 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 2A5F2C433D6; Mon, 1 Aug 2022 11:56:17 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1659354978; bh=5hFJJ5gAtqb4rt193r1r4mkbDulYR0rJCVrXO3f4blY=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=dxRzUA/bXlIhHaw2cvz3oPTAPI/LYrdtybBh6rxFwbE6tL+/yvqngOWmBV7qZPCEu b2i2EXV4jNVmJHf54q2PiWD4jYtmGS9zOfq1QD8k6Z6OwB23NQXw6WiUSD45dzhjPv VY3PxljB4CChHMXBxkiyhgU27HXBhfr/U5lgaPjs= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, syzbot+03d7b43290037d1f87ca@syzkaller.appspotmail.com, David Howells , keyrings@vger.kernel.org, Linus Torvalds Subject: [PATCH 5.18 19/88] watch_queue: Fix missing locking in add_watch_to_object() Date: Mon, 1 Aug 2022 13:46:33 +0200 Message-Id: <20220801114138.914986548@linuxfoundation.org> X-Mailer: git-send-email 2.37.1 In-Reply-To: <20220801114138.041018499@linuxfoundation.org> References: <20220801114138.041018499@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: keyrings@vger.kernel.org From: Linus Torvalds commit e64ab2dbd882933b65cd82ff6235d705ad65dbb6 upstream. If a watch is being added to a queue, it needs to guard against interference from addition of a new watch, manual removal of a watch and removal of a watch due to some other queue being destroyed. KEYCTL_WATCH_KEY guards against this for the same {key,queue} pair by holding the key->sem writelocked and by holding refs on both the key and the queue - but that doesn't prevent interaction from other {key,queue} pairs. While add_watch_to_object() does take the spinlock on the event queue, it doesn't take the lock on the source's watch list. The assumption was that the caller would prevent that (say by taking key->sem) - but that doesn't prevent interference from the destruction of another queue. Fix this by locking the watcher list in add_watch_to_object(). Fixes: c73be61cede5 ("pipe: Add general notification queue support") Reported-by: syzbot+03d7b43290037d1f87ca@syzkaller.appspotmail.com Signed-off-by: David Howells cc: keyrings@vger.kernel.org Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman --- kernel/watch_queue.c | 58 +++++++++++++++++++++++++++++++-------------------- 1 file changed, 36 insertions(+), 22 deletions(-) --- a/kernel/watch_queue.c +++ b/kernel/watch_queue.c @@ -454,6 +454,33 @@ void init_watch(struct watch *watch, str rcu_assign_pointer(watch->queue, wqueue); } +static int add_one_watch(struct watch *watch, struct watch_list *wlist, struct watch_queue *wqueue) +{ + const struct cred *cred; + struct watch *w; + + hlist_for_each_entry(w, &wlist->watchers, list_node) { + struct watch_queue *wq = rcu_access_pointer(w->queue); + if (wqueue == wq && watch->id == w->id) + return -EBUSY; + } + + cred = current_cred(); + if (atomic_inc_return(&cred->user->nr_watches) > task_rlimit(current, RLIMIT_NOFILE)) { + atomic_dec(&cred->user->nr_watches); + return -EAGAIN; + } + + watch->cred = get_cred(cred); + rcu_assign_pointer(watch->watch_list, wlist); + + kref_get(&wqueue->usage); + kref_get(&watch->usage); + hlist_add_head(&watch->queue_node, &wqueue->watches); + hlist_add_head_rcu(&watch->list_node, &wlist->watchers); + return 0; +} + /** * add_watch_to_object - Add a watch on an object to a watch list * @watch: The watch to add @@ -468,34 +495,21 @@ void init_watch(struct watch *watch, str */ int add_watch_to_object(struct watch *watch, struct watch_list *wlist) { - struct watch_queue *wqueue = rcu_access_pointer(watch->queue); - struct watch *w; + struct watch_queue *wqueue; + int ret = -ENOENT; - hlist_for_each_entry(w, &wlist->watchers, list_node) { - struct watch_queue *wq = rcu_access_pointer(w->queue); - if (wqueue == wq && watch->id == w->id) - return -EBUSY; - } - - watch->cred = get_current_cred(); - rcu_assign_pointer(watch->watch_list, wlist); - - if (atomic_inc_return(&watch->cred->user->nr_watches) > - task_rlimit(current, RLIMIT_NOFILE)) { - atomic_dec(&watch->cred->user->nr_watches); - put_cred(watch->cred); - return -EAGAIN; - } + rcu_read_lock(); + wqueue = rcu_access_pointer(watch->queue); if (lock_wqueue(wqueue)) { - kref_get(&wqueue->usage); - kref_get(&watch->usage); - hlist_add_head(&watch->queue_node, &wqueue->watches); + spin_lock(&wlist->lock); + ret = add_one_watch(watch, wlist, wqueue); + spin_unlock(&wlist->lock); unlock_wqueue(wqueue); } - hlist_add_head_rcu(&watch->list_node, &wlist->watchers); - return 0; + rcu_read_unlock(); + return ret; } EXPORT_SYMBOL(add_watch_to_object);