From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from smtp.codeaurora.org by pdx-caf-mail.web.codeaurora.org (Dovecot) with LMTP id usILGdJJGVteUgAAmS7hNA ; Thu, 07 Jun 2018 15:06:16 +0000 Received: by smtp.codeaurora.org (Postfix, from userid 1000) id 43482608B8; Thu, 7 Jun 2018 15:06:16 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on pdx-caf-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.9 required=2.0 tests=BAYES_00,MAILING_LIST_MULTI autolearn=ham autolearn_force=no version=3.4.0 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by smtp.codeaurora.org (Postfix) with ESMTP id AAD956063F; Thu, 7 Jun 2018 15:06:15 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 smtp.codeaurora.org AAD956063F Authentication-Results: pdx-caf-mail.web.codeaurora.org; dmarc=none (p=none dis=none) header.from=decadent.org.uk Authentication-Results: pdx-caf-mail.web.codeaurora.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S936054AbeFGPFo (ORCPT + 25 others); Thu, 7 Jun 2018 11:05:44 -0400 Received: from shadbolt.e.decadent.org.uk ([88.96.1.126]:41570 "EHLO shadbolt.e.decadent.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933405AbeFGPEH (ORCPT ); Thu, 7 Jun 2018 11:04:07 -0400 Received: from [148.252.241.226] (helo=deadeye) by shadbolt.decadent.org.uk with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.84_2) (envelope-from ) id 1fQvbb-0005hK-Jz; Thu, 07 Jun 2018 15:09:35 +0100 Received: from ben by deadeye with local (Exim 4.91) (envelope-from ) id 1fQvb8-00034a-4e; Thu, 07 Jun 2018 15:09:06 +0100 Content-Type: text/plain; charset="UTF-8" Content-Disposition: inline Content-Transfer-Encoding: 8bit MIME-Version: 1.0 From: Ben Hutchings To: linux-kernel@vger.kernel.org, stable@vger.kernel.org CC: akpm@linux-foundation.org, syzbot+d7a918a7a8e1c952bc36@syzkaller.appspotmail.com, "Yisheng Xie" , "Greg Kroah-Hartman" Date: Thu, 07 Jun 2018 15:05:21 +0100 Message-ID: X-Mailer: LinuxStableQueue (scripts by bwh) Subject: [PATCH 3.16 249/410] staging: android: ashmem: Fix possible deadlock in ashmem_ioctl In-Reply-To: X-SA-Exim-Connect-IP: 148.252.241.226 X-SA-Exim-Mail-From: ben@decadent.org.uk X-SA-Exim-Scanned: No (on shadbolt.decadent.org.uk); SAEximRunCond expanded to false Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.16.57-rc1 review patch. If anyone has any objections, please let me know. ------------------ From: Yisheng Xie commit 740a5759bf222332fbb5eda42f89aa25ba38f9b2 upstream. ashmem_mutex may create a chain of dependencies like: CPU0 CPU1 mmap syscall ioctl syscall -> mmap_sem (acquired) -> ashmem_ioctl -> ashmem_mmap -> ashmem_mutex (acquired) -> ashmem_mutex (try to acquire) -> copy_from_user -> mmap_sem (try to acquire) There is a lock odering problem between mmap_sem and ashmem_mutex causing a lockdep splat[1] during a syzcaller test. This patch fixes the problem by move copy_from_user out of ashmem_mutex. [1] https://www.spinics.net/lists/kernel/msg2733200.html Fixes: ce8a3a9e76d0 (staging: android: ashmem: Fix a race condition in pin ioctls) Reported-by: syzbot+d7a918a7a8e1c952bc36@syzkaller.appspotmail.com Signed-off-by: Yisheng Xie Signed-off-by: Greg Kroah-Hartman Signed-off-by: Ben Hutchings --- drivers/staging/android/ashmem.c | 8 +++----- 1 file changed, 3 insertions(+), 5 deletions(-) --- a/drivers/staging/android/ashmem.c +++ b/drivers/staging/android/ashmem.c @@ -703,16 +703,14 @@ static int ashmem_pin_unpin(struct ashme size_t pgstart, pgend; int ret = -EINVAL; + if (unlikely(copy_from_user(&pin, p, sizeof(pin)))) + return -EFAULT; + mutex_lock(&ashmem_mutex); if (unlikely(!asma->file)) goto out_unlock; - if (unlikely(copy_from_user(&pin, p, sizeof(pin)))) { - ret = -EFAULT; - goto out_unlock; - } - /* per custom, you can pass zero for len to mean "everything onward" */ if (!pin.len) pin.len = PAGE_ALIGN(asma->size) - pin.offset;