From: Matthew Wilcox <willy@linux.intel.com>
Date: Wed, 3 Feb 2016 00:57:55 +0000 (-0800)
Subject: drivers/hwspinlock: fix race between radix tree insertion and lookup
X-Git-Url: https://git.karo-electronics.de/?a=commitdiff_plain;h=c6400ba7e13a41539342f1b6e1f9e78419cb0148;p=linux-beck.git

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

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>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---

diff --git a/drivers/hwspinlock/hwspinlock_core.c b/drivers/hwspinlock/hwspinlock_core.c
index 52f708bcf77f..d50c701b19d6 100644
--- a/drivers/hwspinlock/hwspinlock_core.c
+++ b/drivers/hwspinlock/hwspinlock_core.c
@@ -313,6 +313,10 @@ int of_hwspin_lock_get_id(struct device_node *np, int index)
 		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;