| From b2a616676839e2a6b02c8e40be7f886f882ed194 Mon Sep 17 00:00:00 2001 |
| From: Desmond Cheong Zhi Xi <desmondcheongzx@gmail.com> |
| Date: Tue, 27 Jul 2021 15:13:03 +0800 |
| Subject: btrfs: fix rw device counting in __btrfs_free_extra_devids |
| |
| From: Desmond Cheong Zhi Xi <desmondcheongzx@gmail.com> |
| |
| commit b2a616676839e2a6b02c8e40be7f886f882ed194 upstream. |
| |
| When removing a writeable device in __btrfs_free_extra_devids, the rw |
| device count should be decremented. |
| |
| This error was caught by Syzbot which reported a warning in |
| close_fs_devices: |
| |
| WARNING: CPU: 1 PID: 9355 at fs/btrfs/volumes.c:1168 close_fs_devices+0x763/0x880 fs/btrfs/volumes.c:1168 |
| Modules linked in: |
| CPU: 0 PID: 9355 Comm: syz-executor552 Not tainted 5.13.0-rc1-syzkaller #0 |
| Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 |
| RIP: 0010:close_fs_devices+0x763/0x880 fs/btrfs/volumes.c:1168 |
| RSP: 0018:ffffc9000333f2f0 EFLAGS: 00010293 |
| RAX: ffffffff8365f5c3 RBX: 0000000000000001 RCX: ffff888029afd4c0 |
| RDX: 0000000000000000 RSI: 0000000000000001 RDI: 0000000000000000 |
| RBP: ffff88802846f508 R08: ffffffff8365f525 R09: ffffed100337d128 |
| R10: ffffed100337d128 R11: 0000000000000000 R12: dffffc0000000000 |
| R13: ffff888019be8868 R14: 1ffff1100337d10d R15: 1ffff1100337d10a |
| FS: 00007f6f53828700(0000) GS:ffff8880b9a00000(0000) knlGS:0000000000000000 |
| CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 |
| CR2: 000000000047c410 CR3: 00000000302a6000 CR4: 00000000001506f0 |
| DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 |
| DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 |
| Call Trace: |
| btrfs_close_devices+0xc9/0x450 fs/btrfs/volumes.c:1180 |
| open_ctree+0x8e1/0x3968 fs/btrfs/disk-io.c:3693 |
| btrfs_fill_super fs/btrfs/super.c:1382 [inline] |
| btrfs_mount_root+0xac5/0xc60 fs/btrfs/super.c:1749 |
| legacy_get_tree+0xea/0x180 fs/fs_context.c:592 |
| vfs_get_tree+0x86/0x270 fs/super.c:1498 |
| fc_mount fs/namespace.c:993 [inline] |
| vfs_kern_mount+0xc9/0x160 fs/namespace.c:1023 |
| btrfs_mount+0x3d3/0xb50 fs/btrfs/super.c:1809 |
| legacy_get_tree+0xea/0x180 fs/fs_context.c:592 |
| vfs_get_tree+0x86/0x270 fs/super.c:1498 |
| do_new_mount fs/namespace.c:2905 [inline] |
| path_mount+0x196f/0x2be0 fs/namespace.c:3235 |
| do_mount fs/namespace.c:3248 [inline] |
| __do_sys_mount fs/namespace.c:3456 [inline] |
| __se_sys_mount+0x2f9/0x3b0 fs/namespace.c:3433 |
| do_syscall_64+0x3f/0xb0 arch/x86/entry/common.c:47 |
| entry_SYSCALL_64_after_hwframe+0x44/0xae |
| |
| Because fs_devices->rw_devices was not 0 after |
| closing all devices. Here is the call trace that was observed: |
| |
| btrfs_mount_root(): |
| btrfs_scan_one_device(): |
| device_list_add(); <---------------- device added |
| btrfs_open_devices(): |
| open_fs_devices(): |
| btrfs_open_one_device(); <-------- writable device opened, |
| rw device count ++ |
| btrfs_fill_super(): |
| open_ctree(): |
| btrfs_free_extra_devids(): |
| __btrfs_free_extra_devids(); <--- writable device removed, |
| rw device count not decremented |
| fail_tree_roots: |
| btrfs_close_devices(): |
| close_fs_devices(); <------- rw device count off by 1 |
| |
| As a note, prior to commit cf89af146b7e ("btrfs: dev-replace: fail |
| mount if we don't have replace item with target device"), rw_devices |
| was decremented on removing a writable device in |
| __btrfs_free_extra_devids only if the BTRFS_DEV_STATE_REPLACE_TGT bit |
| was not set for the device. However, this check does not need to be |
| reinstated as it is now redundant and incorrect. |
| |
| In __btrfs_free_extra_devids, we skip removing the device if it is the |
| target for replacement. This is done by checking whether device->devid |
| == BTRFS_DEV_REPLACE_DEVID. Since BTRFS_DEV_STATE_REPLACE_TGT is set |
| only on the device with devid BTRFS_DEV_REPLACE_DEVID, no devices |
| should have the BTRFS_DEV_STATE_REPLACE_TGT bit set after the check, |
| and so it's redundant to test for that bit. |
| |
| Additionally, following commit 82372bc816d7 ("Btrfs: make |
| the logic of source device removing more clear"), rw_devices is |
| incremented whenever a writeable device is added to the alloc |
| list (including the target device in btrfs_dev_replace_finishing), so |
| all removals of writable devices from the alloc list should also be |
| accompanied by a decrement to rw_devices. |
| |
| Reported-by: syzbot+a70e2ad0879f160b9217@syzkaller.appspotmail.com |
| Fixes: cf89af146b7e ("btrfs: dev-replace: fail mount if we don't have replace item with target device") |
| CC: stable@vger.kernel.org # 5.10+ |
| Tested-by: syzbot+a70e2ad0879f160b9217@syzkaller.appspotmail.com |
| Reviewed-by: Anand Jain <anand.jain@oracle.com> |
| Signed-off-by: Desmond Cheong Zhi Xi <desmondcheongzx@gmail.com> |
| Signed-off-by: David Sterba <dsterba@suse.com> |
| Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
| --- |
| fs/btrfs/volumes.c | 1 + |
| 1 file changed, 1 insertion(+) |
| |
| --- a/fs/btrfs/volumes.c |
| +++ b/fs/btrfs/volumes.c |
| @@ -1077,6 +1077,7 @@ static void __btrfs_free_extra_devids(st |
| if (test_bit(BTRFS_DEV_STATE_WRITEABLE, &device->dev_state)) { |
| list_del_init(&device->dev_alloc_list); |
| clear_bit(BTRFS_DEV_STATE_WRITEABLE, &device->dev_state); |
| + fs_devices->rw_devices--; |
| } |
| list_del_init(&device->dev_list); |
| fs_devices->num_devices--; |