From patchwork Thu Aug 20 09:19:53 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Greg KH X-Patchwork-Id: 265401 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 AB716C433DF for ; Thu, 20 Aug 2020 12:45:39 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 88C2F2086A for ; Thu, 20 Aug 2020 12:45:39 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1597927539; bh=RaKFugCKuZ3leuKfF6Xlf6z2dztIZXYGEQs17Aqa4uA=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=p2SPlpYB5854CxTPPYNhdBaE/2cwxZtGudyS0w721gvWkLnWcon6zeCTJbLcvc9K+ Is6MJqyWxOj2H/HTlYf+W3jq+aShXMG2IdKJI8X0wGAUF57jNypj+CyM8X6kwyEasd GurPn6v7IvnI0jWO58AZH3LSoUqvyU7RT1Pza30U= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729339AbgHTMpQ (ORCPT ); Thu, 20 Aug 2020 08:45:16 -0400 Received: from mail.kernel.org ([198.145.29.99]:45788 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729068AbgHTJpm (ORCPT ); Thu, 20 Aug 2020 05:45:42 -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 D9C7A22CF6; Thu, 20 Aug 2020 09:45:28 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1597916729; bh=RaKFugCKuZ3leuKfF6Xlf6z2dztIZXYGEQs17Aqa4uA=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=v+mopblLt6FAm8ds8m+JV/YYZpZatPP2JFV6AMhhqAyUIuAsaSbnBJwQVCNMqQQkk MWYLa/OyUB62+R8xslWiBhqgvRyNMdF2xIwlBvfCHn9CCuWWu10mpjEpHDGrpOC1tw PN5/me1uCPXLHaCfAYyGzsXP0wGs3Q31ZnBH4ZU4= 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 5.4 026/152] btrfs: inode: fix NULL pointer dereference if inode doesnt need compression Date: Thu, 20 Aug 2020 11:19:53 +0200 Message-Id: <20200820091555.001479760@linuxfoundation.org> X-Mailer: git-send-email 2.28.0 In-Reply-To: <20200820091553.615456912@linuxfoundation.org> References: <20200820091553.615456912@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 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 @@ -641,12 +641,18 @@ 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; } }