From: Catalin Marinas catalin.marinas@arm.com

Since the actual slab freeing is deferred when calling kvfree_rcu(), so is the kmemleak_free() callback informing kmemleak of the object deletion. From the perspective of the kvfree_rcu() caller, the object is freed and it may remove any references to it. Since kmemleak does not scan RCU internal data storing the pointer, it will report such objects as leaks during the grace period.

Tell kmemleak to ignore such objects on the kvfree_call_rcu() path. Note that the tiny RCU implementation does not have such issue since the objects can be tracked from the rcu_ctrlblk structure.

Signed-off-by: Catalin Marinas catalin.marinas@arm.com Reported-by: Christoph Paasch cpaasch@apple.com Closes: https://lore.kernel.org/all/F903A825-F05F-4B77-A2B5-7356282FBA2C@apple.com/ Cc: stable@vger.kernel.org Tested-by: Christoph Paasch cpaasch@apple.com Reviewed-by: Paul E. McKenney paulmck@kernel.org Signed-off-by: Joel Fernandes (Google) joel@joelfernandes.org Signed-off-by: Frederic Weisbecker frederic@kernel.org --- kernel/rcu/tree.c | 9 +++++++++ 1 file changed, 9 insertions(+)

diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c index a83ecab77917..4dd7df30df31 100644 --- a/kernel/rcu/tree.c +++ b/kernel/rcu/tree.c @@ -31,6 +31,7 @@ #include <linux/bitops.h> #include <linux/export.h> #include <linux/completion.h> +#include <linux/kmemleak.h> #include <linux/moduleparam.h> #include <linux/panic.h> #include <linux/panic_notifier.h> @@ -3389,6 +3390,14 @@ void kvfree_call_rcu(struct rcu_head *head, void *ptr) success = true; }

+ /* + * The kvfree_rcu() caller considers the pointer freed at this point + * and likely removes any references to it. Since the actual slab + * freeing (and kmemleak_free()) is deferred, tell kmemleak to ignore + * this object (no scanning or false positives reporting). + */ + kmemleak_ignore(ptr); + // Set timer to drain after KFREE_DRAIN_JIFFIES. if (rcu_scheduler_active == RCU_SCHEDULER_RUNNING) schedule_delayed_monitor_work(krcp);