From: Anand Jain anand.jain@oracle.com
commit cf89af146b7e62af55470cf5f3ec3c56ec144a5e upstream.
If there is a device BTRFS_DEV_REPLACE_DEVID without the device replace item, then it means the filesystem is inconsistent state. This is either corruption or a crafted image. Fail the mount as this needs a closer look what is actually wrong.
As of now if BTRFS_DEV_REPLACE_DEVID is present without the replace item, in __btrfs_free_extra_devids() we determine that there is an extra device, and free those extra devices but continue to mount the device. However, we were wrong in keeping tack of the rw_devices so the syzbot testcase failed:
WARNING: CPU: 1 PID: 3612 at fs/btrfs/volumes.c:1166 close_fs_devices.part.0+0x607/0x800 fs/btrfs/volumes.c:1166 Kernel panic - not syncing: panic_on_warn set ... CPU: 1 PID: 3612 Comm: syz-executor.2 Not tainted 5.9.0-rc4-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Call Trace: __dump_stack lib/dump_stack.c:77 [inline] dump_stack+0x198/0x1fd lib/dump_stack.c:118 panic+0x347/0x7c0 kernel/panic.c:231 __warn.cold+0x20/0x46 kernel/panic.c:600 report_bug+0x1bd/0x210 lib/bug.c:198 handle_bug+0x38/0x90 arch/x86/kernel/traps.c:234 exc_invalid_op+0x14/0x40 arch/x86/kernel/traps.c:254 asm_exc_invalid_op+0x12/0x20 arch/x86/include/asm/idtentry.h:536 RIP: 0010:close_fs_devices.part.0+0x607/0x800 fs/btrfs/volumes.c:1166 RSP: 0018:ffffc900091777e0 EFLAGS: 00010246 RAX: 0000000000040000 RBX: ffffffffffffffff RCX: ffffc9000c8b7000 RDX: 0000000000040000 RSI: ffffffff83097f47 RDI: 0000000000000007 RBP: dffffc0000000000 R08: 0000000000000001 R09: ffff8880988a187f R10: 0000000000000000 R11: 0000000000000001 R12: ffff88809593a130 R13: ffff88809593a1ec R14: ffff8880988a1908 R15: ffff88809593a050 close_fs_devices fs/btrfs/volumes.c:1193 [inline] btrfs_close_devices+0x95/0x1f0 fs/btrfs/volumes.c:1179 open_ctree+0x4984/0x4a2d fs/btrfs/disk-io.c:3434 btrfs_fill_super fs/btrfs/super.c:1316 [inline] btrfs_mount_root.cold+0x14/0x165 fs/btrfs/super.c:1672
The fix here is, when we determine that there isn't a replace item then fail the mount if there is a replace target device (devid 0).
CC: stable@vger.kernel.org # 4.19+ Reported-by: syzbot+4cfe71a4da060be47502@syzkaller.appspotmail.com Signed-off-by: Anand Jain anand.jain@oracle.com Reviewed-by: David Sterba dsterba@suse.com Signed-off-by: David Sterba dsterba@suse.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- fs/btrfs/dev-replace.c | 26 ++++++++++++++++++++++++-- fs/btrfs/volumes.c | 26 +++++++------------------- 2 files changed, 31 insertions(+), 21 deletions(-)
--- a/fs/btrfs/dev-replace.c +++ b/fs/btrfs/dev-replace.c @@ -95,6 +95,17 @@ int btrfs_init_dev_replace(struct btrfs_ ret = btrfs_search_slot(NULL, dev_root, &key, path, 0, 0); if (ret) { no_valid_dev_replace_entry_found: + /* + * We don't have a replace item or it's corrupted. If there is + * a replace target, fail the mount. + */ + if (btrfs_find_device(fs_info->fs_devices, + BTRFS_DEV_REPLACE_DEVID, NULL, NULL, false)) { + btrfs_err(fs_info, + "found replace target device without a valid replace item"); + ret = -EUCLEAN; + goto out; + } ret = 0; dev_replace->replace_state = BTRFS_IOCTL_DEV_REPLACE_STATE_NEVER_STARTED; @@ -147,8 +158,19 @@ no_valid_dev_replace_entry_found: case BTRFS_IOCTL_DEV_REPLACE_STATE_NEVER_STARTED: case BTRFS_IOCTL_DEV_REPLACE_STATE_FINISHED: case BTRFS_IOCTL_DEV_REPLACE_STATE_CANCELED: - dev_replace->srcdev = NULL; - dev_replace->tgtdev = NULL; + /* + * We don't have an active replace item but if there is a + * replace target, fail the mount. + */ + if (btrfs_find_device(fs_info->fs_devices, + BTRFS_DEV_REPLACE_DEVID, NULL, NULL, false)) { + btrfs_err(fs_info, + "replace devid present without an active replace item"); + ret = -EUCLEAN; + } else { + dev_replace->srcdev = NULL; + dev_replace->tgtdev = NULL; + } break; case BTRFS_IOCTL_DEV_REPLACE_STATE_STARTED: case BTRFS_IOCTL_DEV_REPLACE_STATE_SUSPENDED: --- a/fs/btrfs/volumes.c +++ b/fs/btrfs/volumes.c @@ -1064,22 +1064,13 @@ again: continue; }
- if (device->devid == BTRFS_DEV_REPLACE_DEVID) { - /* - * In the first step, keep the device which has - * the correct fsid and the devid that is used - * for the dev_replace procedure. - * In the second step, the dev_replace state is - * read from the device tree and it is known - * whether the procedure is really active or - * not, which means whether this device is - * used or whether it should be removed. - */ - if (step == 0 || test_bit(BTRFS_DEV_STATE_REPLACE_TGT, - &device->dev_state)) { - continue; - } - } + /* + * We have already validated the presence of BTRFS_DEV_REPLACE_DEVID, + * in btrfs_init_dev_replace() so just continue. + */ + if (device->devid == BTRFS_DEV_REPLACE_DEVID) + continue; + if (device->bdev) { blkdev_put(device->bdev, device->mode); device->bdev = NULL; @@ -1088,9 +1079,6 @@ again: 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); - if (!test_bit(BTRFS_DEV_STATE_REPLACE_TGT, - &device->dev_state)) - fs_devices->rw_devices--; } list_del_init(&device->dev_list); fs_devices->num_devices--;