Patch "drivers/hwspinlock: fix race between radix tree insertion and lookup" has been added to the 4.4-stable tree

[<gregkh@linuxfoundation.org>]

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

    drivers/hwspinlock: fix race between radix tree insertion and lookup

to the 4.4-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:
     drivers-hwspinlock-fix-race-between-radix-tree-insertion-and-lookup.patch
and it can be found in the queue-4.4 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 c6400ba7e13a41539342f1b6e1f9e78419cb0148 Mon Sep 17 00:00:00 2001
From: Matthew Wilcox <willy@linux.intel.com>
Date: Tue, 2 Feb 2016 16:57:55 -0800
Subject: drivers/hwspinlock: fix race between radix tree insertion and lookup

From: Matthew Wilcox <willy@linux.intel.com>

commit c6400ba7e13a41539342f1b6e1f9e78419cb0148 upstream.

of_hwspin_lock_get_id() is protected by the RCU lock, which means that
insertions can occur simultaneously with the lookup.  If the radix tree
transitions from a height of 0, we can see a slot with the indirect_ptr
bit set, which will cause us to at least read random memory, and could
cause other havoc.

Fix this by using the newly introduced radix_tree_iter_retry().

Signed-off-by: Matthew Wilcox <willy@linux.intel.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Ohad Ben-Cohen <ohad@wizery.com>
Cc: Konstantin Khlebnikov <khlebnikov@openvz.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 drivers/hwspinlock/hwspinlock_core.c |    4 ++++
 1 file changed, 4 insertions(+)

--- a/drivers/hwspinlock/hwspinlock_core.c
+++ b/drivers/hwspinlock/hwspinlock_core.c
@@ -313,6 +313,10 @@ int of_hwspin_lock_get_id(struct device_
 		hwlock = radix_tree_deref_slot(slot);
 		if (unlikely(!hwlock))
 			continue;
+		if (radix_tree_is_indirect_ptr(hwlock)) {
+			slot = radix_tree_iter_retry(&iter);
+			continue;
+		}
 
 		if (hwlock->bank->dev->of_node == args.np) {
 			ret = 0;


Patches currently in stable-queue which might be from willy@linux.intel.com are

queue-4.4/radix-tree-fix-oops-after-radix_tree_iter_retry.patch
queue-4.4/drivers-hwspinlock-fix-race-between-radix-tree-insertion-and-lookup.patch
queue-4.4/radix-tree-fix-race-in-gang-lookup.patch
queue-4.4/devm_memremap_release-fix-memremap-d-addr-handling.patch