[PATCH 2/3] btrfs: restore active device pointers after failed sprout

[Guanghui Yang]

btrfs_init_new_device() switches latest_dev and possibly s_bdev from the
seed device to the new sprout device before creating the first writable
chunks.

If chunk creation or the subsequent sprout setup fails, the error path
releases the new device without switching those pointers back.
btrfs_show_devname() can then dereference the freed latest_dev and crash.

Restore the active device pointers to the latest seed device before
removing and releasing the failed sprout device.

Fixes: b7cb29e666fe ("btrfs: update latest_dev when we create a sprout device")
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Guanghui Yang <3497809730@xxxxxx>
---
 fs/btrfs/volumes.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index 556d8a60a5ec..a14f186f5b07 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -3070,6 +3070,9 @@ int btrfs_init_new_device(struct btrfs_fs_info *fs_info, const char *device_path
 error_sysfs:
 	btrfs_sysfs_remove_device(device);
 	mutex_lock(&fs_info->fs_devices->device_list_mutex);
+	if (seeding_dev)
+		btrfs_assign_next_active_device(device,
+						seed_devices->latest_dev);
 	mutex_lock(&fs_info->chunk_mutex);
 	if (!list_empty(&device->post_commit_list))
 		list_del_init(&device->post_commit_list);
-- 
2.52.0.windows.1