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=-9.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SIGNED_OFF_BY,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 258D9C433DF for ; Thu, 20 Aug 2020 13:55:56 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id EF5F820758 for ; Thu, 20 Aug 2020 13:55:55 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1597931756; bh=gyy4mqRPaLXTrrYs++HIfHK5fw84SdLNy01wdRVzCMo=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=1zOu/lQh/gIXBWSkVEdLXQa8Ip4fS1DLAhJ/zaOE/sof0y8hpAGF0gKN9ijvZBvoD 4pQHiLsn/NsZi3dEVmcgx5ZYAZrlj7k30L00Y/noho+2SPgwSQv+F3/Re7LSjPkMqJ dLrRVtiQ3MiLeTYVuvMR7Ibsq8f4d0bXTP8DuxPc= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729578AbgHTNzt (ORCPT ); Thu, 20 Aug 2020 09:55:49 -0400 Received: from mail.kernel.org ([198.145.29.99]:35480 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727884AbgHTJ01 (ORCPT ); Thu, 20 Aug 2020 05:26:27 -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 F3A912224D; Thu, 20 Aug 2020 09:26:25 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1597915586; bh=gyy4mqRPaLXTrrYs++HIfHK5fw84SdLNy01wdRVzCMo=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=yZX3HePWcgWXz6EFFPp3OXTPqLGLXSFjONGjjPAJMKIDn4ZXH0l1Cs+AiX28QFl0w RpL6gTI2NYHlOYwtXIJYkbUMYSqQlIlr3pAXUWephmj0VcCea8PV9HD9VOCtXFUxXS H2g0CkbfRN26UYZbv/pZbb7mXz8sRBiNZOYkfK+w= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Luciano Chavez , Qu Wenruo , David Sterba Subject: [PATCH 5.8 036/232] btrfs: inode: fix NULL pointer dereference if inode doesnt need compression Date: Thu, 20 Aug 2020 11:18:07 +0200 Message-Id: <20200820091614.520145024@linuxfoundation.org> X-Mailer: git-send-email 2.28.0 In-Reply-To: <20200820091612.692383444@linuxfoundation.org> References: <20200820091612.692383444@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Qu Wenruo commit 1e6e238c3002ea3611465ce5f32777ddd6a40126 upstream. [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: Greg Kroah-Hartman --- fs/btrfs/inode.c | 16 +++++++++++----- 1 file changed, 11 insertions(+), 5 deletions(-) --- a/fs/btrfs/inode.c +++ b/fs/btrfs/inode.c @@ -650,12 +650,18 @@ 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 0; } }