[PATCH 6.1 0127/1146] timerqueue: Use rb_entry_safe() in timerqueue_getnext()

Greg Kroah-Hartman
2022-12-28T15:14:37Z

From: Barnabás Pőcze <pobrn@protonmail.com>

[ Upstream commit 2f117484329b233455ee278f2d9b0a4356835060 ]

When `timerqueue_getnext()` is called on an empty timer queue, it will
use `rb_entry()` on a NULL pointer, which is invalid. Fix that by using
`rb_entry_safe()` which handles NULL pointers.

This has not caused any issues so far because the offset of the `rb_node`
member in `timerqueue_node` is 0, so `rb_entry()` is essentially a no-op.

Fixes: 511885d7061e ("lib/timerqueue: Rely on rbtree semantics for next timer")
Signed-off-by: Barnabás Pőcze <pobrn@protonmail.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20221114195421.342929-1-pobrn@protonmail.com
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
include/linux/timerqueue.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/linux/timerqueue.h b/include/linux/timerqueue.h
index 93884086f392..adc80e29168e 100644
--- a/include/linux/timerqueue.h
+++ b/include/linux/timerqueue.h
@@ -35,7 +35,7 @@ struct timerqueue_node *timerqueue_getnext(struct timerqueue_head *head)
{
struct rb_node *leftmost = rb_first_cached(&head->rb_root);

- return rb_entry(leftmost, struct timerqueue_node, node);
+ return rb_entry_safe(leftmost, struct timerqueue_node, node);
}

static inline void timerqueue_init(struct timerqueue_node *node)
--
2.35.1