From patchwork Tue Jan 5 09:29:07 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Greg Kroah-Hartman X-Patchwork-Id: 357433 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=-18.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER, INCLUDES_PATCH, MAILING_LIST_MULTI, SPF_HELO_NONE, SPF_PASS, 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 7717BC433E9 for ; Tue, 5 Jan 2021 09:31:33 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 5487220756 for ; Tue, 5 Jan 2021 09:31:33 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728279AbhAEJ30 (ORCPT ); Tue, 5 Jan 2021 04:29:26 -0500 Received: from mail.kernel.org ([198.145.29.99]:49316 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728286AbhAEJ30 (ORCPT ); Tue, 5 Jan 2021 04:29:26 -0500 Received: by mail.kernel.org (Postfix) with ESMTPSA id 0706F229F0; Tue, 5 Jan 2021 09:28:27 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1609838908; bh=mtQPt8Uzwmc/6ANODzPvsmDmtJPeyUPnzbZaKro9OuM=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=lLLEA1Dp+q0PgzmekcLNVkgzWgWQM2bo0USx6NDUbc4tLNm+pNmEwBIjsxn8wBy20 WdmNVPGT0AFlXZnHWjC6HRw3tXxicT7Hh/40iFHr9VlioU7DLxfnh3DX54WlNitgVM dcu91H8w7UwiqwzR4+xUu9azpimhQbU8iGOSyPBw= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, syzbot+22e87cdf94021b984aa6@syzkaller.appspotmail.com, syzbot+c5e32344981ad9f33750@syzkaller.appspotmail.com, Boqun Feng , Jeff Layton Subject: [PATCH 4.19 21/29] fcntl: Fix potential deadlock in send_sig{io, urg}() Date: Tue, 5 Jan 2021 10:29:07 +0100 Message-Id: <20210105090821.261970196@linuxfoundation.org> X-Mailer: git-send-email 2.30.0 In-Reply-To: <20210105090818.518271884@linuxfoundation.org> References: <20210105090818.518271884@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Boqun Feng commit 8d1ddb5e79374fb277985a6b3faa2ed8631c5b4c upstream. Syzbot reports a potential deadlock found by the newly added recursive read deadlock detection in lockdep: [...] ======================================================== [...] WARNING: possible irq lock inversion dependency detected [...] 5.9.0-rc2-syzkaller #0 Not tainted [...] -------------------------------------------------------- [...] syz-executor.1/10214 just changed the state of lock: [...] ffff88811f506338 (&f->f_owner.lock){.+..}-{2:2}, at: send_sigurg+0x1d/0x200 [...] 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 *** The corresponding deadlock case is as followed: CPU 0 CPU 1 CPU 2 read_lock(&fown->lock); spin_lock_irqsave(&dev->event_lock, ...) write_lock_irq(&filp->f_owner.lock); // wait for the lock read_lock(&fown-lock); // have to wait until the writer release // due to the fairness spin_lock_irqsave(&dev->event_lock); // wait for the lock The lock dependency on CPU 1 happens if there exists a call sequence: input_inject_event(): spin_lock_irqsave(&dev->event_lock,...); input_handle_event(): input_pass_values(): input_to_handler(): handler->event(): // evdev_event() evdev_pass_values(): spin_lock(&client->buffer_lock); __pass_event(): kill_fasync(): kill_fasync_rcu(): read_lock(&fa->fa_lock); send_sigio(): read_lock(&fown->lock); To fix this, make the reader in send_sigurg() and send_sigio() use read_lock_irqsave() and read_lock_irqrestore(). Reported-by: syzbot+22e87cdf94021b984aa6@syzkaller.appspotmail.com Reported-by: syzbot+c5e32344981ad9f33750@syzkaller.appspotmail.com Signed-off-by: Boqun Feng Signed-off-by: Jeff Layton Signed-off-by: Greg Kroah-Hartman --- fs/fcntl.c | 10 ++++++---- 1 file changed, 6 insertions(+), 4 deletions(-) --- a/fs/fcntl.c +++ b/fs/fcntl.c @@ -779,9 +779,10 @@ void send_sigio(struct fown_struct *fown { struct task_struct *p; enum pid_type type; + unsigned long flags; struct pid *pid; - read_lock(&fown->lock); + read_lock_irqsave(&fown->lock, flags); type = fown->pid_type; pid = fown->pid; @@ -802,7 +803,7 @@ void send_sigio(struct fown_struct *fown read_unlock(&tasklist_lock); } out_unlock_fown: - read_unlock(&fown->lock); + read_unlock_irqrestore(&fown->lock, flags); } static void send_sigurg_to_task(struct task_struct *p, @@ -817,9 +818,10 @@ int send_sigurg(struct fown_struct *fown struct task_struct *p; enum pid_type type; struct pid *pid; + unsigned long flags; int ret = 0; - read_lock(&fown->lock); + read_lock_irqsave(&fown->lock, flags); type = fown->pid_type; pid = fown->pid; @@ -842,7 +844,7 @@ int send_sigurg(struct fown_struct *fown read_unlock(&tasklist_lock); } out_unlock_fown: - read_unlock(&fown->lock); + read_unlock_irqrestore(&fown->lock, flags); return ret; }