From patchwork Fri Jul 24 02:00:25 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Qu Wenruo X-Patchwork-Id: 11681893 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 61FD313B1 for ; Fri, 24 Jul 2020 02:00:35 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 433DC2068F for ; Fri, 24 Jul 2020 02:00:35 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726559AbgGXCAe (ORCPT ); Thu, 23 Jul 2020 22:00:34 -0400 Received: from mx2.suse.de ([195.135.220.15]:46882 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726381AbgGXCAe (ORCPT ); Thu, 23 Jul 2020 22:00:34 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id 27CBAAE7A; Fri, 24 Jul 2020 02:00:40 +0000 (UTC) From: Qu Wenruo To: linux-btrfs@vger.kernel.org Cc: stable@vger.kernel.org, Johannes Thumshirn , David Sterba Subject: [PATCH 1/2] btrfs: reloc: fix reloc root leak and NULL pointer dereference Date: Fri, 24 Jul 2020 10:00:25 +0800 Message-Id: <20200724020027.31751-1-wqu@suse.com> X-Mailer: git-send-email 2.27.0 MIME-Version: 1.0 Sender: linux-btrfs-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-btrfs@vger.kernel.org commit 51415b6c1b117e223bc083e30af675cb5c5498f3 upstream. [BUG] When balance is canceled, there is a pretty high chance that unmounting the fs can lead to lead the NULL pointer dereference: BTRFS warning (device dm-3): page private not zero on page 223158272 ... BTRFS warning (device dm-3): page private not zero on page 223162368 BTRFS error (device dm-3): leaked root 18446744073709551608-304 refcount 1 BUG: kernel NULL pointer dereference, address: 0000000000000168 #PF: supervisor read access in kernel mode #PF: error_code(0x0000) - not-present page PGD 0 P4D 0 Oops: 0000 [#1] PREEMPT SMP NOPTI CPU: 2 PID: 5793 Comm: umount Tainted: G O 5.7.0-rc5-custom+ #53 Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 0.0.0 02/06/2015 RIP: 0010:__lock_acquire+0x5dc/0x24c0 Call Trace: lock_acquire+0xab/0x390 _raw_spin_lock+0x39/0x80 btrfs_release_extent_buffer_pages+0xd7/0x200 [btrfs] release_extent_buffer+0xb2/0x170 [btrfs] free_extent_buffer+0x66/0xb0 [btrfs] btrfs_put_root+0x8e/0x130 [btrfs] btrfs_check_leaked_roots.cold+0x5/0x5d [btrfs] btrfs_free_fs_info+0xe5/0x120 [btrfs] btrfs_kill_super+0x1f/0x30 [btrfs] deactivate_locked_super+0x3b/0x80 deactivate_super+0x3e/0x50 cleanup_mnt+0x109/0x160 __cleanup_mnt+0x12/0x20 task_work_run+0x67/0xa0 exit_to_usermode_loop+0xc5/0xd0 syscall_return_slowpath+0x205/0x360 do_syscall_64+0x6e/0xb0 entry_SYSCALL_64_after_hwframe+0x49/0xb3 RIP: 0033:0x7fd028ef740b [CAUSE] When balance is canceled, all reloc roots are marked as orphan, and orphan reloc roots are going to be cleaned up. However for orphan reloc roots and merged reloc roots, their lifespan are quite different: Merged reloc roots | Orphan reloc roots by cancel -------------------------------------------------------------------- create_reloc_root() | create_reloc_root() |- refs == 1 | |- refs == 1 | btrfs_grab_root(reloc_root); | btrfs_grab_root(reloc_root); |- refs == 2 | |- refs == 2 | root->reloc_root = reloc_root; | root->reloc_root = reloc_root; >>> No difference so far <<< | prepare_to_merge() | prepare_to_merge() |- btrfs_set_root_refs(item, 1);| |- if (!err) (err == -EINTR) | merge_reloc_roots() | merge_reloc_roots() |- merge_reloc_root() | |- Doing nothing to put reloc root |- insert_dirty_subvol() | |- refs == 2 |- __del_reloc_root() | |- btrfs_put_root() | |- refs == 1 | >>> Now orphan reloc roots still have refs 2 <<< | clean_dirty_subvols() | clean_dirty_subvols() |- btrfs_drop_snapshot() | |- btrfS_drop_snapshot() |- reloc_root get freed | |- reloc_root still has refs 2 | related ebs get freed, but | reloc_root still recorded in | allocated_roots btrfs_check_leaked_roots() | btrfs_check_leaked_roots() |- No leaked roots | |- Leaked reloc_roots detected | |- btrfs_put_root() | |- free_extent_buffer(root->node); | |- eb already freed, caused NULL | pointer dereference [FIX] The fix is to clear fs_root->reloc_root and put it at merge_reloc_roots() time, so that we won't leak reloc roots. Fixes: d2311e698578 ("btrfs: relocation: Delay reloc tree deletion after merge_reloc_roots") CC: stable@vger.kernel.org # 5.4.x Tested-by: Johannes Thumshirn Signed-off-by: Qu Wenruo [Manually solve the conflicts due to no btrfs root refs rework] Signed-off-by: David Sterba --- fs/btrfs/relocation.c | 9 ++++++--- 1 file changed, 6 insertions(+), 3 deletions(-) diff --git a/fs/btrfs/relocation.c b/fs/btrfs/relocation.c index e890f09e2073..3f8c706d75ee 100644 --- a/fs/btrfs/relocation.c +++ b/fs/btrfs/relocation.c @@ -2525,12 +2525,10 @@ void merge_reloc_roots(struct reloc_control *rc) reloc_root = list_entry(reloc_roots.next, struct btrfs_root, root_list); + root = read_fs_root(fs_info, reloc_root->root_key.offset); if (btrfs_root_refs(&reloc_root->root_item) > 0) { - root = read_fs_root(fs_info, - reloc_root->root_key.offset); BUG_ON(IS_ERR(root)); BUG_ON(root->reloc_root != reloc_root); - ret = merge_reloc_root(rc, root); if (ret) { if (list_empty(&reloc_root->root_list)) @@ -2539,6 +2537,11 @@ void merge_reloc_roots(struct reloc_control *rc) goto out; } } else { + if (!IS_ERR(root)) { + if (root->reloc_root == reloc_root) + root->reloc_root = NULL; + } + list_del_init(&reloc_root->root_list); /* Don't forget to queue this reloc root for cleanup */ list_add_tail(&reloc_root->reloc_dirty_list, From patchwork Fri Jul 24 02:00:26 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Qu Wenruo X-Patchwork-Id: 11681895 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 0911513B4 for ; Fri, 24 Jul 2020 02:00:38 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id E582D20792 for ; Fri, 24 Jul 2020 02:00:37 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726737AbgGXCAh (ORCPT ); Thu, 23 Jul 2020 22:00:37 -0400 Received: from mx2.suse.de ([195.135.220.15]:46896 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726381AbgGXCAh (ORCPT ); Thu, 23 Jul 2020 22:00:37 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id CB33BB130; Fri, 24 Jul 2020 02:00:43 +0000 (UTC) From: Qu Wenruo To: linux-btrfs@vger.kernel.org Cc: stable@vger.kernel.org, David Sterba Subject: [PATCH 2/2] btrfs: reloc: clear DEAD_RELOC_TREE bit for orphan roots to prevent runaway balance Date: Fri, 24 Jul 2020 10:00:26 +0800 Message-Id: <20200724020027.31751-2-wqu@suse.com> X-Mailer: git-send-email 2.27.0 In-Reply-To: <20200724020027.31751-1-wqu@suse.com> References: <20200724020027.31751-1-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 commit 1dae7e0e58b484eaa43d530f211098fdeeb0f404 upstream. [BUG] There are several reported runaway balance, that balance is flooding the log with "found X extents" where the X never changes. [CAUSE] Commit d2311e698578 ("btrfs: relocation: Delay reloc tree deletion after merge_reloc_roots") introduced BTRFS_ROOT_DEAD_RELOC_TREE bit to indicate that one subvolume has finished its tree blocks swap with its reloc tree. However if balance is canceled or hits ENOSPC halfway, we didn't clear the BTRFS_ROOT_DEAD_RELOC_TREE bit, leaving that bit hanging forever until unmount. Any subvolume root with that bit, would cause backref cache to skip this tree block, as it has finished its tree block swap. This would cause all tree blocks of that root be ignored by balance, leading to runaway balance. [FIX] Fix the problem by also clearing the BTRFS_ROOT_DEAD_RELOC_TREE bit for the original subvolume of orphan reloc root. Add an umount check for the stale bit still set. Fixes: d2311e698578 ("btrfs: relocation: Delay reloc tree deletion after merge_reloc_roots") Cc: # 5.4.x Signed-off-by: Qu Wenruo [Manually solve the conflicts due to no btrfs root refs rework] Signed-off-by: David Sterba --- fs/btrfs/relocation.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/fs/btrfs/relocation.c b/fs/btrfs/relocation.c index 3f8c706d75ee..1b087ee338cc 100644 --- a/fs/btrfs/relocation.c +++ b/fs/btrfs/relocation.c @@ -2540,6 +2540,8 @@ void merge_reloc_roots(struct reloc_control *rc) if (!IS_ERR(root)) { if (root->reloc_root == reloc_root) root->reloc_root = NULL; + clear_bit(BTRFS_ROOT_DEAD_RELOC_TREE, + &root->state); } list_del_init(&reloc_root->root_list);