Patch "rbd: don't leak parent_spec in rbd_dev_probe_parent()" has been added to the 4.2-stable tree

Patch "rbd: don't leak parent_spec in rbd_dev_probe_parent()" has been added to the 4.2-stable tree

[gregkh]

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

    rbd: don't leak parent_spec in rbd_dev_probe_parent()

to the 4.2-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:
     rbd-don-t-leak-parent_spec-in-rbd_dev_probe_parent.patch
and it can be found in the queue-4.2 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From 1f2c6651f69c14d0d3a9cfbda44ea101b02160ba Mon Sep 17 00:00:00 2001
From: Ilya Dryomov <idryomov@gmail.com>
Date: Sun, 11 Oct 2015 19:38:00 +0200
Subject: rbd: don't leak parent_spec in rbd_dev_probe_parent()

From: Ilya Dryomov <idryomov@gmail.com>

commit 1f2c6651f69c14d0d3a9cfbda44ea101b02160ba upstream.

Currently we leak parent_spec and trigger a "parent reference
underflow" warning if rbd_dev_create() in rbd_dev_probe_parent() fails.
The problem is we take the !parent out_err branch and that only drops
refcounts; parent_spec that would've been freed had we called
rbd_dev_unparent() remains and triggers rbd_warn() in
rbd_dev_parent_put() - at that point we have parent_spec != NULL and
parent_ref == 0, so counter ends up being -1 after the decrement.

Redo rbd_dev_probe_parent() to fix this.

Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
Reviewed-by: Alex Elder <elder@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 drivers/block/rbd.c |   36 ++++++++++++++++--------------------
 1 file changed, 16 insertions(+), 20 deletions(-)

--- a/drivers/block/rbd.c
+++ b/drivers/block/rbd.c
@@ -5175,41 +5175,37 @@ out_err:
 static int rbd_dev_probe_parent(struct rbd_device *rbd_dev)
 {
 	struct rbd_device *parent = NULL;
-	struct rbd_spec *parent_spec;
-	struct rbd_client *rbdc;
 	int ret;
 
 	if (!rbd_dev->parent_spec)
 		return 0;
-	/*
-	 * We need to pass a reference to the client and the parent
-	 * spec when creating the parent rbd_dev.  Images related by
-	 * parent/child relationships always share both.
-	 */
-	parent_spec = rbd_spec_get(rbd_dev->parent_spec);
-	rbdc = __rbd_get_client(rbd_dev->rbd_client);
 
-	ret = -ENOMEM;
-	parent = rbd_dev_create(rbdc, parent_spec, NULL);
-	if (!parent)
+	parent = rbd_dev_create(rbd_dev->rbd_client, rbd_dev->parent_spec,
+				NULL);
+	if (!parent) {
+		ret = -ENOMEM;
 		goto out_err;
+	}
+
+	/*
+	 * Images related by parent/child relationships always share
+	 * rbd_client and spec/parent_spec, so bump their refcounts.
+	 */
+	__rbd_get_client(rbd_dev->rbd_client);
+	rbd_spec_get(rbd_dev->parent_spec);
 
 	ret = rbd_dev_image_probe(parent, false);
 	if (ret < 0)
 		goto out_err;
+
 	rbd_dev->parent = parent;
 	atomic_set(&rbd_dev->parent_ref, 1);
-
 	return 0;
+
 out_err:
-	if (parent) {
-		rbd_dev_unparent(rbd_dev);
+	rbd_dev_unparent(rbd_dev);
+	if (parent)
 		rbd_dev_destroy(parent);
-	} else {
-		rbd_put_client(rbdc);
-		rbd_spec_put(parent_spec);
-	}
-
 	return ret;
 }
 


Patches currently in stable-queue which might be from idryomov@gmail.com are

queue-4.2/rbd-prevent-kernel-stack-blow-up-on-rbd-map.patch
queue-4.2/rbd-require-stable-pages-if-message-data-crcs-are-enabled.patch
queue-4.2/rbd-don-t-leak-parent_spec-in-rbd_dev_probe_parent.patch