5.4-stable review patch. If anyone has any objections, please let me know.
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From: Uladzislau Rezki (Sony) urezki@gmail.com
[ Upstream commit 33b6a1f155d627f5bd80c7485c598ce45428f74f ]
Currently the call_rcu() API does not check whether a callback pointer is NULL. If NULL is passed, rcu_core() will try to invoke it, resulting in NULL pointer dereference and a kernel crash.
To prevent this and improve debuggability, this patch adds a check for NULL and emits a kernel stack trace to help identify a faulty caller.
Signed-off-by: Uladzislau Rezki (Sony) urezki@gmail.com Reviewed-by: Joel Fernandes joelagnelf@nvidia.com Signed-off-by: Joel Fernandes joelagnelf@nvidia.com Signed-off-by: Sasha Levin sashal@kernel.org --- kernel/rcu/tree.c | 4 ++++ 1 file changed, 4 insertions(+)
diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c index 615283404d9dc..562c1ff452837 100644 --- a/kernel/rcu/tree.c +++ b/kernel/rcu/tree.c @@ -2568,6 +2568,10 @@ __call_rcu(struct rcu_head *head, rcu_callback_t func, bool lazy) /* Misaligned rcu_head! */ WARN_ON_ONCE((unsigned long)head & (sizeof(void *) - 1));
+ /* Avoid NULL dereference if callback is NULL. */ + if (WARN_ON_ONCE(!func)) + return; + if (debug_rcu_head_queue(head)) { /* * Probable double call_rcu(), so leak the callback.