[4.2.y-ckt stable] Patch "drivers/hwspinlock: fix race between radix tree insertion and lookup" has been added to the 4.2.y-ckt tree
Kamal Mostafa
kamal at canonical.com
Mon Mar 7 22:32:18 UTC 2016
This is a note to let you know that I have just added a patch titled
drivers/hwspinlock: fix race between radix tree insertion and lookup
to the linux-4.2.y-queue branch of the 4.2.y-ckt extended stable tree
which can be found at:
http://kernel.ubuntu.com/git/ubuntu/linux.git/log/?h=linux-4.2.y-queue
This patch is scheduled to be released in version 4.2.8-ckt5.
If you, or anyone else, feels it should not be added to this tree, please
reply to this email.
For more information about the 4.2.y-ckt tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable
Thanks.
-Kamal
---8<------------------------------------------------------------
>From 25de31dfccb0a50c4593d51dab4776cf392f1af1 Mon Sep 17 00:00:00 2001
From: Matthew Wilcox <willy at linux.intel.com>
Date: Tue, 2 Feb 2016 16:57:55 -0800
Subject: drivers/hwspinlock: fix race between radix tree insertion and lookup
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 at linux.intel.com>
Cc: Hugh Dickins <hughd at google.com>
Cc: Ohad Ben-Cohen <ohad at wizery.com>
Cc: Konstantin Khlebnikov <khlebnikov at openvz.org>
Signed-off-by: Andrew Morton <akpm at linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds at linux-foundation.org>
Signed-off-by: Kamal Mostafa <kamal at canonical.com>
---
drivers/hwspinlock/hwspinlock_core.c | 4 ++++
1 file changed, 4 insertions(+)
diff --git a/drivers/hwspinlock/hwspinlock_core.c b/drivers/hwspinlock/hwspinlock_core.c
index 52f708b..d50c701 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;
--
2.7.0
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