| From | Greg Kroah-Hartman <> | Subject | [PATCH 4.4 115/137] drivers/hwspinlock: fix race between radix tree insertion and lookup | Date | Tue, 23 Feb 2016 19:34:06 -0800 |
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4.4-stable review patch. If anyone has any objections, please let me know.
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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;
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