[PATCH 5.9 190/255] btrfs: dev-replace: fail mount if we dont have replace item with target device

Greg Kroah-Hartman
2020-11-17T13:40:59Z

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--;