From patchwork Mon Aug 24 08:30:59 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Greg KH X-Patchwork-Id: 265095 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=-13.7 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED, DKIM_VALID, HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH, MAILING_LIST_MULTI, SIGNED_OFF_BY, SPF_HELO_NONE, SPF_PASS, 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 38A56C433E1 for ; Mon, 24 Aug 2020 09:21:40 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 188EB2074D for ; Mon, 24 Aug 2020 09:21:40 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1598260900; bh=yzddTpnn2h210LpLCaM7zxT/uiMjrpvCKxK9gRPQYAE=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=UT07FVK1PzaLQmRAqAsLXD11VDbzFB+NvzSK4vpRbe4vK/0oqowR763A0cBGQkoPU 1x3P64cbi7bs2DvhCgBY4LHrYZ2YJ2HHLWHfO4xtWksjNWAdFnS1sMTFBmR13MJ6ng 6UhZpTcjk2MjY5cbkOwp6AfbJebMQBQgPlztbgdk= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726871AbgHXJVj (ORCPT ); Mon, 24 Aug 2020 05:21:39 -0400 Received: from mail.kernel.org ([198.145.29.99]:38242 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730196AbgHXIzq (ORCPT ); Mon, 24 Aug 2020 04:55:46 -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 BA6D72074D; Mon, 24 Aug 2020 08:55:44 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1598259345; bh=yzddTpnn2h210LpLCaM7zxT/uiMjrpvCKxK9gRPQYAE=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=uHysMcqa+VIXYWCdOYvNY+za9/rKpFZFx0yGnv1/+6LbROIGsleVvFCkLGzU2+lZo lDLvJJXdJaaGWDSyRp8bZPOkvv06M6oePgz8A3zWDVMSMQKXgRPXNtEWcEeieuA+qc o07Aq//5tf5hCwAmc38Am2h+zIwIJEGXhhBp/YNs= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Luciano Chavez , Qu Wenruo , David Sterba , Sasha Levin Subject: [PATCH 4.19 08/71] btrfs: inode: fix NULL pointer dereference if inode doesnt need compression Date: Mon, 24 Aug 2020 10:30:59 +0200 Message-Id: <20200824082356.292830154@linuxfoundation.org> X-Mailer: git-send-email 2.28.0 In-Reply-To: <20200824082355.848475917@linuxfoundation.org> References: <20200824082355.848475917@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: Qu Wenruo [ Upstream commit 1e6e238c3002ea3611465ce5f32777ddd6a40126 ] [BUG] There is a bug report of NULL pointer dereference caused in compress_file_extent(): Oops: Kernel access of bad area, sig: 11 [#1] LE PAGE_SIZE=64K MMU=Hash SMP NR_CPUS=2048 NUMA pSeries Workqueue: btrfs-delalloc btrfs_delalloc_helper [btrfs] NIP [c008000006dd4d34] compress_file_range.constprop.41+0x75c/0x8a0 [btrfs] LR [c008000006dd4d1c] compress_file_range.constprop.41+0x744/0x8a0 [btrfs] Call Trace: [c000000c69093b00] [c008000006dd4d1c] compress_file_range.constprop.41+0x744/0x8a0 [btrfs] (unreliable) [c000000c69093bd0] [c008000006dd4ebc] async_cow_start+0x44/0xa0 [btrfs] [c000000c69093c10] [c008000006e14824] normal_work_helper+0xdc/0x598 [btrfs] [c000000c69093c80] [c0000000001608c0] process_one_work+0x2c0/0x5b0 [c000000c69093d10] [c000000000160c38] worker_thread+0x88/0x660 [c000000c69093db0] [c00000000016b55c] kthread+0x1ac/0x1c0 [c000000c69093e20] [c00000000000b660] ret_from_kernel_thread+0x5c/0x7c ---[ end trace f16954aa20d822f6 ]--- [CAUSE] For the following execution route of compress_file_range(), it's possible to hit NULL pointer dereference: compress_file_extent() |- pages = NULL; |- start = async_chunk->start = 0; |- end = async_chunk = 4095; |- nr_pages = 1; |- inode_need_compress() == false; <<< Possible, see later explanation | Now, we have nr_pages = 1, pages = NULL |- cont: |- ret = cow_file_range_inline(); |- if (ret <= 0) { |- for (i = 0; i < nr_pages; i++) { |- WARN_ON(pages[i]->mapping); <<< Crash To enter above call execution branch, we need the following race: Thread 1 (chattr) | Thread 2 (writeback) --------------------------+------------------------------ | btrfs_run_delalloc_range | |- inode_need_compress = true | |- cow_file_range_async() btrfs_ioctl_set_flag() | |- binode_flags |= | BTRFS_INODE_NOCOMPRESS | | compress_file_range() | |- inode_need_compress = false | |- nr_page = 1 while pages = NULL | | Then hit the crash [FIX] This patch will fix it by checking @pages before doing accessing it. This patch is only designed as a hot fix and easy to backport. More elegant fix may make btrfs only check inode_need_compress() once to avoid such race, but that would be another story. Reported-by: Luciano Chavez Fixes: 4d3a800ebb12 ("btrfs: merge nr_pages input and output parameter in compress_pages") CC: stable@vger.kernel.org # 4.14.x: cecc8d9038d16: btrfs: Move free_pages_out label in inline extent handling branch in compress_file_range CC: stable@vger.kernel.org # 4.14+ Signed-off-by: Qu Wenruo Signed-off-by: David Sterba Signed-off-by: Sasha Levin --- fs/btrfs/inode.c | 15 +++++++++++---- 1 file changed, 11 insertions(+), 4 deletions(-) diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c index 8507192cd6449..bdfe159a60da6 100644 --- a/fs/btrfs/inode.c +++ b/fs/btrfs/inode.c @@ -629,11 +629,18 @@ cont: page_error_op | PAGE_END_WRITEBACK); - for (i = 0; i < nr_pages; i++) { - WARN_ON(pages[i]->mapping); - put_page(pages[i]); + /* + * Ensure we only free the compressed pages if we have + * them allocated, as we can still reach here with + * inode_need_compress() == false. + */ + if (pages) { + for (i = 0; i < nr_pages; i++) { + WARN_ON(pages[i]->mapping); + put_page(pages[i]); + } + kfree(pages); } - kfree(pages); return; }