From patchwork Wed Dec 11 05:00:04 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Qu Wenruo X-Patchwork-Id: 11284265 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 1426C13B6 for ; Wed, 11 Dec 2019 05:00:18 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id F08B420836 for ; Wed, 11 Dec 2019 05:00:17 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726524AbfLKFAQ (ORCPT ); Wed, 11 Dec 2019 00:00:16 -0500 Received: from mx2.suse.de ([195.135.220.15]:45532 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726487AbfLKFAQ (ORCPT ); Wed, 11 Dec 2019 00:00:16 -0500 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 D4F3BAE07; Wed, 11 Dec 2019 05:00:14 +0000 (UTC) From: Qu Wenruo To: linux-btrfs@vger.kernel.org Cc: Zygo Blaxell Subject: [PATCH 3/3] btrfs: relocation: Fix a KASAN report on btrfs_reloc_pre_snapshot() due to extended reloc root lifespan Date: Wed, 11 Dec 2019 13:00:04 +0800 Message-Id: <20191211050004.18414-4-wqu@suse.com> X-Mailer: git-send-email 2.24.0 In-Reply-To: <20191211050004.18414-1-wqu@suse.com> References: <20191211050004.18414-1-wqu@suse.com> MIME-Version: 1.0 Sender: linux-btrfs-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-btrfs@vger.kernel.org [BUG] When running workload with balance start/cancel, snapshot creation/deletion and fsstress, we can hit the following KASAN report: ================================================================== BUG: KASAN: use-after-free in btrfs_reloc_pre_snapshot+0x85/0xc0 [btrfs] Read of size 4 at addr ffff888157140100 by task btrfs/1822 CPU: 2 PID: 1822 Comm: btrfs Tainted: G O 5.5.0-rc1-custom+ #40 Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 0.0.0 02/06/2015 Call Trace: dump_stack+0xc2/0x11a print_address_description.constprop.0+0x20/0x210 __kasan_report.cold+0x1b/0x41 kasan_report+0x12/0x20 check_memory_region+0x13c/0x1b0 __asan_loadN+0xf/0x20 btrfs_reloc_pre_snapshot+0x85/0xc0 [btrfs] create_pending_snapshot+0x209/0x15f0 [btrfs] create_pending_snapshots+0x111/0x140 [btrfs] btrfs_commit_transaction+0x7a6/0x1360 [btrfs] btrfs_mksubvol+0x915/0x960 [btrfs] btrfs_ioctl_snap_create_transid+0x1d5/0x1e0 [btrfs] btrfs_ioctl_snap_create_v2+0x1d3/0x270 [btrfs] btrfs_ioctl+0x241b/0x3e60 [btrfs] do_vfs_ioctl+0x831/0xb10 ksys_ioctl+0x67/0x90 __x64_sys_ioctl+0x43/0x50 do_syscall_64+0x79/0xe0 entry_SYSCALL_64_after_hwframe+0x49/0xbe [CAUSE] Again, we try to access root->reloc_root without verify if that reloc root is already dead (being freed). [FIX] Check if the root has dead reloc root before accessing it. Reported-by: Zygo Blaxell Fixes: d2311e698578 ("btrfs: relocation: Delay reloc tree deletion after merge_reloc_roots") Signed-off-by: Qu Wenruo Reviewed-by: Josef Bacik --- fs/btrfs/relocation.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/fs/btrfs/relocation.c b/fs/btrfs/relocation.c index 619ccb183515..2d2cd1596ec9 100644 --- a/fs/btrfs/relocation.c +++ b/fs/btrfs/relocation.c @@ -4721,7 +4721,8 @@ void btrfs_reloc_pre_snapshot(struct btrfs_pending_snapshot *pending, struct btrfs_root *root = pending->root; struct reloc_control *rc = root->fs_info->reloc_ctl; - if (!root->reloc_root || !rc) + if (!root->reloc_root || !rc || test_bit(BTRFS_ROOT_DEAD_RELOC_TREE, + &root->state)) return; if (!rc->merge_reloc_tree)