From patchwork Tue Mar 10 12:37:38 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Greg KH X-Patchwork-Id: 229761 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=-9.8 required=3.0 tests=DKIMWL_WL_HIGH, DKIM_SIGNED, DKIM_VALID, HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH, MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=ham 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 C510AC18E5A for ; Tue, 10 Mar 2020 12:48:13 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 9B07C2468D for ; Tue, 10 Mar 2020 12:48:13 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1583844493; bh=LPWEOXXHH5EmBECDqoJMdQuy16xACdmF1Y8tC/ZfenU=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=ZFd3vDyeNSZzNoSqzIo/2qFg+gEeB34wibOW7T/9phLrGQfY6Ol4AJslwmc986RBL LQzVvq7QqYwR6p3Yw2/cEchTdzThQvB+1Pkq4E4FvQ2uWXzriDur0guZSMoslYq5P/ gofag7PPDE6ZG32DBuG8xDOvqNQ0g8TpZL2RDkZ8= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728286AbgCJMsM (ORCPT ); Tue, 10 Mar 2020 08:48:12 -0400 Received: from mail.kernel.org ([198.145.29.99]:52196 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727624AbgCJMsM (ORCPT ); Tue, 10 Mar 2020 08:48:12 -0400 Received: from localhost (83-86-89-107.cable.dynamic.v4.ziggo.nl [83.86.89.107]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 268CD2467D; Tue, 10 Mar 2020 12:48:11 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1583844491; bh=LPWEOXXHH5EmBECDqoJMdQuy16xACdmF1Y8tC/ZfenU=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=ISNzU1erqjKptA/FMheDcF6Rswpg186h0RL7qXxxylTz6q6IwPUldff8quAosXRZm XuQOMsymy1NYmsVsqRJUNGX12gC1Apvn1sNbzN/Hi4syaeh7dBqOzPr7Ycd/kRfUCX 1OaGJJPneofpsvCMdwCHUyJLi5JC94L06moqr9To= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Ming Lei , Bob Liu , "Steven Rostedt (VMware)" , Cengiz Can , Jens Axboe , Sasha Levin Subject: [PATCH 5.4 012/168] blktrace: fix dereference after null check Date: Tue, 10 Mar 2020 13:37:38 +0100 Message-Id: <20200310123636.981272933@linuxfoundation.org> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20200310123635.322799692@linuxfoundation.org> References: <20200310123635.322799692@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Sender: stable-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Cengiz Can [ Upstream commit 153031a301bb07194e9c37466cfce8eacb977621 ] There was a recent change in blktrace.c that added a RCU protection to `q->blk_trace` in order to fix a use-after-free issue during access. However the change missed an edge case that can lead to dereferencing of `bt` pointer even when it's NULL: Coverity static analyzer marked this as a FORWARD_NULL issue with CID 1460458. ``` /kernel/trace/blktrace.c: 1904 in sysfs_blk_trace_attr_store() 1898 ret = 0; 1899 if (bt == NULL) 1900 ret = blk_trace_setup_queue(q, bdev); 1901 1902 if (ret == 0) { 1903 if (attr == &dev_attr_act_mask) >>> CID 1460458: Null pointer dereferences (FORWARD_NULL) >>> Dereferencing null pointer "bt". 1904 bt->act_mask = value; 1905 else if (attr == &dev_attr_pid) 1906 bt->pid = value; 1907 else if (attr == &dev_attr_start_lba) 1908 bt->start_lba = value; 1909 else if (attr == &dev_attr_end_lba) ``` Added a reassignment with RCU annotation to fix the issue. Fixes: c780e86dd48 ("blktrace: Protect q->blk_trace with RCU") Cc: stable@vger.kernel.org Reviewed-by: Ming Lei Reviewed-by: Bob Liu Reviewed-by: Steven Rostedt (VMware) Signed-off-by: Cengiz Can Signed-off-by: Jens Axboe Signed-off-by: Sasha Levin --- kernel/trace/blktrace.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) diff --git a/kernel/trace/blktrace.c b/kernel/trace/blktrace.c index 4b2ad374167bc..e7e483cdbea61 100644 --- a/kernel/trace/blktrace.c +++ b/kernel/trace/blktrace.c @@ -1888,8 +1888,11 @@ static ssize_t sysfs_blk_trace_attr_store(struct device *dev, } ret = 0; - if (bt == NULL) + if (bt == NULL) { ret = blk_trace_setup_queue(q, bdev); + bt = rcu_dereference_protected(q->blk_trace, + lockdep_is_held(&q->blk_trace_mutex)); + } if (ret == 0) { if (attr == &dev_attr_act_mask)