bcache: don't attach backing with duplicate UUID

commit 86755b7a96faed57f910f9e6b8061e019ac1ec08 upstream.

This can happen e.g. during disk cloning.

This is an incomplete fix: it does not catch duplicate UUIDs earlier
when things are still unattached.  It does not unregister the device.
Further changes to cope better with this are planned but conflict with
Coly's ongoing improvements to handling device errors.  In the meantime,
one can manually stop the device after this has happened.

Attempts to attach a duplicate device result in:

[  136.372404] loop: module loaded
[  136.424461] bcache: register_bdev() registered backing device loop0
[  136.424464] bcache: bch_cached_dev_attach() Tried to attach loop0 but duplicate UUID already attached

My test procedure is:

  dd if=/dev/sdb1 of=imgfile bs=1024 count=262144
  losetup -f imgfile

Signed-off-by: Michael Lyle <mlyle@lyle.org>
Reviewed-by: Tang Junhui <tang.junhui@zte.com.cn>
Cc: <stable@vger.kernel.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/md/bcache/super.c b/drivers/md/bcache/super.c
index 1c5e46abc839e715423485241478d26860a135ab..9417170f180a9ff09f3e48d0a99057bd2754e316 100644 (file)
--- a/drivers/md/bcache/super.c
+++ b/drivers/md/bcache/super.c
@@ -938,6 +938,7 @@ int bch_cached_dev_attach(struct cached_dev *dc, struct cache_set *c)
        uint32_t rtime = cpu_to_le32(get_seconds());
        struct uuid_entry *u;
        char buf[BDEVNAME_SIZE];
+       struct cached_dev *exist_dc, *t;
 
        bdevname(dc->bdev, buf);
 
@@ -961,6 +962,16 @@ int bch_cached_dev_attach(struct cached_dev *dc, struct cache_set *c)
                return -EINVAL;
        }
 
+       /* Check whether already attached */
+       list_for_each_entry_safe(exist_dc, t, &c->cached_devs, list) {
+               if (!memcmp(dc->sb.uuid, exist_dc->sb.uuid, 16)) {
+                       pr_err("Tried to attach %s but duplicate UUID already attached",
+                               buf);
+
+                       return -EINVAL;
+               }
+       }
+
        u = uuid_find(c, dc->sb.uuid);
 
        if (u &&