2 files changed, 18 insertions, 3 deletions

diff --git a/drivers/block/drbd/drbd_nl.c b/drivers/block/drbd/drbd_nl.c
index 39e9a91a8f31..9e3f441e7e84 100644
--- a/drivers/block/drbd/drbd_nl.c
+++ b/drivers/block/drbd/drbd_nl.c
@@ -1381,6 +1381,12 @@ int drbd_adm_attach(struct sk_buff *skb, struct genl_info *info)
                 goto fail;
         }
 
+        write_lock_irq(&global_state_lock);
+        retcode = drbd_resync_after_valid(mdev, new_disk_conf->resync_after);
+        write_unlock_irq(&global_state_lock);
+        if (retcode != NO_ERROR)
+                goto fail;
+
         rcu_read_lock();
         nc = rcu_dereference(mdev->tconn->net_conf);
         if (nc) {
diff --git a/drivers/block/drbd/drbd_worker.c b/drivers/block/drbd/drbd_worker.c
index 7f51f88b0a80..891c0ecaa292 100644
--- a/drivers/block/drbd/drbd_worker.c
+++ b/drivers/block/drbd/drbd_worker.c
@@ -1426,7 +1426,7 @@ static int _drbd_may_sync_now(struct drbd_conf *mdev)
         int resync_after;
 
         while (1) {
-                if (!odev->ldev)
+                if (!odev->ldev || odev->state.disk == D_DISKLESS)
                         return 1;
                 rcu_read_lock();
                 resync_after = rcu_dereference(odev->ldev->disk_conf)->resync_after;
@@ -1434,7 +1434,7 @@ static int _drbd_may_sync_now(struct drbd_conf *mdev)
                 if (resync_after == -1)
                         return 1;
                 odev = minor_to_mdev(resync_after);
-                if (!expect(odev))
+                if (!odev)
                         return 1;
                 if ((odev->state.conn >= C_SYNC_SOURCE &&
                      odev->state.conn <= C_PAUSED_SYNC_T) ||
@@ -1516,7 +1516,7 @@ enum drbd_ret_code drbd_resync_after_valid(struct drbd_conf *mdev, int o_minor)
 
         if (o_minor == -1)
                 return NO_ERROR;
-        if (o_minor < -1 || minor_to_mdev(o_minor) == NULL)
+        if (o_minor < -1 || o_minor > MINORMASK)
                 return ERR_RESYNC_AFTER;
 
         /* check for loops */
@@ -1525,6 +1525,15 @@ enum drbd_ret_code drbd_resync_after_valid(struct drbd_conf *mdev, int o_minor)
                 if (odev == mdev)
                         return ERR_RESYNC_AFTER_CYCLE;
 
+                /* You are free to depend on diskless, non-existing,
+                 * or not yet/no longer existing minors.
+                 * We only reject dependency loops.
+                 * We cannot follow the dependency chain beyond a detached or
+                 * missing minor.
+                 */
+                if (!odev || !odev->ldev || odev->state.disk == D_DISKLESS)
+                        return NO_ERROR;
+
                 rcu_read_lock();
                 resync_after = rcu_dereference(odev->ldev->disk_conf)->resync_after;
                 rcu_read_unlock();