Patch "bcache: don't attach backing with duplicate UUID" has been added to the 4.9-stable tree

This is a note to let you know that I've just added the patch titled

bcache: don't attach backing with duplicate UUID

to the 4.9-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
bcache-don-t-attach-backing-with-duplicate-uuid.patch
and it can be found in the queue-4.9 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Michael Lyle <[email protected]>
Date: Mon, 5 Mar 2018 13:41:55 -0800
Subject: bcache: don't attach backing with duplicate UUID

From: Michael Lyle <[email protected]>

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

---
 drivers/md/bcache/super.c |   11 +++++++++++
 1 file changed, 11 insertions(+)

@@ -937,6 +937,7 @@ int bch_cached_dev_attach(struct cached_
 	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);
 

@@ -960,6 +961,16 @@ int bch_cached_dev_attach(struct cached_
 		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 &&

Patches currently in stable-queue which might be from [email protected] are

queue-4.9/bcache-fix-crashes-in-duplicate-cache-device-register.patch queue-4.9/bcache-don-t-attach-backing-with-duplicate-uuid.patch