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=-9.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,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 89AA0C43381 for ; Mon, 18 Mar 2019 02:48:26 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 62D4B20857 for ; Mon, 18 Mar 2019 02:48:26 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727691AbfCRCsZ (ORCPT ); Sun, 17 Mar 2019 22:48:25 -0400 Received: from mx2.suse.de ([195.135.220.15]:38178 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1727201AbfCRCsZ (ORCPT ); Sun, 17 Mar 2019 22:48:25 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id 03E1CAEFF for ; Mon, 18 Mar 2019 02:48:24 +0000 (UTC) From: Qu Wenruo To: linux-btrfs@vger.kernel.org Subject: [PATCH] btrfs: reloc: Fix NULL pointer dereference due to expanded reloc_root lifespan Date: Mon, 18 Mar 2019 10:48:19 +0800 Message-Id: <20190318024819.18716-1-wqu@suse.com> X-Mailer: git-send-email 2.21.0 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: linux-btrfs-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-btrfs@vger.kernel.org Commit 514e70150b60 ("btrfs: relocation: Delay reloc tree deletion after merge_reloc_roots()") expands the life span of root->reloc_root. This breaks certain check on fs_info->reloc_ctl. Before that commit, if we have a root with valid reloc_root, then it's ensured to have fs_info->reloc_ctl. But now since reloc_root doesn't always mean a valid fs_info->reloc_ctl, such check is unreliable and can cause the following NULL pointer dereference: BUG: unable to handle kernel NULL pointer dereference at 00000000000005c1 IP: btrfs_reloc_pre_snapshot+0x20/0x50 [btrfs] PGD 0 P4D 0 Oops: 0000 [#1] SMP PTI CPU: 0 PID: 10379 Comm: snapperd Not tainted 4.12.14-lp150.12.53-default #1 openSUSE Leap 15.0 Call Trace: create_pending_snapshot+0xd7/0xfc0 [btrfs] create_pending_snapshots+0x8e/0xb0 [btrfs] btrfs_commit_transaction+0x2ac/0x8f0 [btrfs] btrfs_mksubvol+0x561/0x570 [btrfs] btrfs_ioctl_snap_create_transid+0x189/0x190 [btrfs] btrfs_ioctl_snap_create_v2+0x102/0x150 [btrfs] btrfs_ioctl+0x5c9/0x1e60 [btrfs] do_vfs_ioctl+0x90/0x5f0 SyS_ioctl+0x74/0x80 do_syscall_64+0x7b/0x150 entry_SYSCALL_64_after_hwframe+0x3d/0xa2 RIP: 0033:0x7fd7cdab8467 Fix it by explicitly checking fs_info->reloc_ctl other than using the implied root->reloc_root. Fixes: 514e70150b60 ("btrfs: relocation: Delay reloc tree deletion after merge_reloc_roots()") Signed-off-by: Qu Wenruo --- fs/btrfs/relocation.c | 12 +++++------- 1 file changed, 5 insertions(+), 7 deletions(-) diff --git a/fs/btrfs/relocation.c b/fs/btrfs/relocation.c index ddf028509931..351fa506dc9b 100644 --- a/fs/btrfs/relocation.c +++ b/fs/btrfs/relocation.c @@ -4667,14 +4667,12 @@ int btrfs_reloc_cow_block(struct btrfs_trans_handle *trans, void btrfs_reloc_pre_snapshot(struct btrfs_pending_snapshot *pending, u64 *bytes_to_reserve) { - struct btrfs_root *root; - struct reloc_control *rc; + struct btrfs_root *root = pending->root; + struct reloc_control *rc = root->fs_info->reloc_ctl; - root = pending->root; - if (!root->reloc_root) + if (!root->reloc_root || !rc) return; - rc = root->fs_info->reloc_ctl; if (!rc->merge_reloc_tree) return; @@ -4703,10 +4701,10 @@ int btrfs_reloc_post_snapshot(struct btrfs_trans_handle *trans, struct btrfs_root *root = pending->root; struct btrfs_root *reloc_root; struct btrfs_root *new_root; - struct reloc_control *rc; + struct reloc_control *rc = root->fs_info->reloc_ctl; int ret; - if (!root->reloc_root) + if (!root->reloc_root || !rc) return 0; rc = root->fs_info->reloc_ctl; -- 2.21.0