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 X-Spam-Level: X-Spam-Status: No, score=-19.1 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_GIT autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 586AFC433F5 for ; Mon, 13 Sep 2021 14:24:13 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 4014360EC0 for ; Mon, 13 Sep 2021 14:24:13 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1343929AbhIMOZY (ORCPT ); Mon, 13 Sep 2021 10:25:24 -0400 Received: from mail.kernel.org ([198.145.29.99]:40122 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1345926AbhIMOU1 (ORCPT ); Mon, 13 Sep 2021 10:20:27 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 8450260555; Mon, 13 Sep 2021 13:46:34 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1631540795; bh=62YYar+mdw0Dk2wJcjESavjQkmC+SW+ycjRjxCHh2Rw=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=tyqjDZlKN6tzPxAaCPlLhH30XRhfZyQemSSjVhWdKclOcoT4T9Hd2sAxrKFZ3Sbwq lzSM5kpJnTiBxwb+7jAA513N2Oc6eDiJyY3br6bEtuRJLeWdGErUPE0XmJcI0ITrCG bb29lgojJ56EgK4/+c8KI2zOwVK3V3JTlkYhXLkY= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Desmond Cheong Zhi Xi , Jeff Layton , Sasha Levin , syzbot+e6d5398a02c516ce5e70@syzkaller.appspotmail.com Subject: [PATCH 5.14 038/334] fcntl: fix potential deadlocks for &fown_struct.lock Date: Mon, 13 Sep 2021 15:11:32 +0200 Message-Id: <20210913131114.720248866@linuxfoundation.org> X-Mailer: git-send-email 2.33.0 In-Reply-To: <20210913131113.390368911@linuxfoundation.org> References: <20210913131113.390368911@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: linux-kernel@vger.kernel.org From: Desmond Cheong Zhi Xi [ Upstream commit f671a691e299f58835d4660d642582bf0e8f6fda ] Syzbot reports a potential deadlock in do_fcntl: ======================================================== WARNING: possible irq lock inversion dependency detected 5.12.0-syzkaller #0 Not tainted -------------------------------------------------------- syz-executor132/8391 just changed the state of lock: ffff888015967bf8 (&f->f_owner.lock){.+..}-{2:2}, at: f_getown_ex fs/fcntl.c:211 [inline] ffff888015967bf8 (&f->f_owner.lock){.+..}-{2:2}, at: do_fcntl+0x8b4/0x1200 fs/fcntl.c:395 but this lock was taken by another, HARDIRQ-safe lock in the past: (&dev->event_lock){-...}-{2:2} and interrupts could create inverse lock ordering between them. other info that might help us debug this: Chain exists of: &dev->event_lock --> &new->fa_lock --> &f->f_owner.lock Possible interrupt unsafe locking scenario: CPU0 CPU1 ---- ---- lock(&f->f_owner.lock); local_irq_disable(); lock(&dev->event_lock); lock(&new->fa_lock); lock(&dev->event_lock); *** DEADLOCK *** This happens because there is a lock hierarchy of &dev->event_lock --> &new->fa_lock --> &f->f_owner.lock from the following call chain: input_inject_event(): spin_lock_irqsave(&dev->event_lock,...); input_handle_event(): input_pass_values(): input_to_handler(): evdev_events(): evdev_pass_values(): spin_lock(&client->buffer_lock); __pass_event(): kill_fasync(): kill_fasync_rcu(): read_lock(&fa->fa_lock); send_sigio(): read_lock_irqsave(&fown->lock,...); However, since &dev->event_lock is HARDIRQ-safe, interrupts have to be disabled while grabbing &f->f_owner.lock, otherwise we invert the lock hierarchy. Hence, we replace calls to read_lock/read_unlock on &f->f_owner.lock, with read_lock_irq/read_unlock_irq. Reported-and-tested-by: syzbot+e6d5398a02c516ce5e70@syzkaller.appspotmail.com Signed-off-by: Desmond Cheong Zhi Xi Signed-off-by: Jeff Layton Signed-off-by: Sasha Levin --- fs/fcntl.c | 13 +++++++------ 1 file changed, 7 insertions(+), 6 deletions(-) diff --git a/fs/fcntl.c b/fs/fcntl.c index f946bec8f1f1..932ec1e9f5bf 100644 --- a/fs/fcntl.c +++ b/fs/fcntl.c @@ -150,7 +150,8 @@ void f_delown(struct file *filp) pid_t f_getown(struct file *filp) { pid_t pid = 0; - read_lock(&filp->f_owner.lock); + + read_lock_irq(&filp->f_owner.lock); rcu_read_lock(); if (pid_task(filp->f_owner.pid, filp->f_owner.pid_type)) { pid = pid_vnr(filp->f_owner.pid); @@ -158,7 +159,7 @@ pid_t f_getown(struct file *filp) pid = -pid; } rcu_read_unlock(); - read_unlock(&filp->f_owner.lock); + read_unlock_irq(&filp->f_owner.lock); return pid; } @@ -208,7 +209,7 @@ static int f_getown_ex(struct file *filp, unsigned long arg) struct f_owner_ex owner = {}; int ret = 0; - read_lock(&filp->f_owner.lock); + read_lock_irq(&filp->f_owner.lock); rcu_read_lock(); if (pid_task(filp->f_owner.pid, filp->f_owner.pid_type)) owner.pid = pid_vnr(filp->f_owner.pid); @@ -231,7 +232,7 @@ static int f_getown_ex(struct file *filp, unsigned long arg) ret = -EINVAL; break; } - read_unlock(&filp->f_owner.lock); + read_unlock_irq(&filp->f_owner.lock); if (!ret) { ret = copy_to_user(owner_p, &owner, sizeof(owner)); @@ -249,10 +250,10 @@ static int f_getowner_uids(struct file *filp, unsigned long arg) uid_t src[2]; int err; - read_lock(&filp->f_owner.lock); + read_lock_irq(&filp->f_owner.lock); src[0] = from_kuid(user_ns, filp->f_owner.uid); src[1] = from_kuid(user_ns, filp->f_owner.euid); - read_unlock(&filp->f_owner.lock); + read_unlock_irq(&filp->f_owner.lock); err = put_user(src[0], &dst[0]); err |= put_user(src[1], &dst[1]); -- 2.30.2