From: "Paul E. McKenney" <paulmck@kernel.org>
To: "Joel Fernandes (Google)" <joel@joelfernandes.org>
Cc: linux-kernel@vger.kernel.org,
Frederic Weisbecker <frederic@kernel.org>,
Neeraj Upadhyay <quic_neeraju@quicinc.com>,
Josh Triplett <josh@joshtriplett.org>,
Boqun Feng <boqun.feng@gmail.com>,
Steven Rostedt <rostedt@goodmis.org>,
Mathieu Desnoyers <mathieu.desnoyers@efficios.com>,
Lai Jiangshan <jiangshanlai@gmail.com>,
Zqiang <qiang.zhang1211@gmail.com>,
Catalin Marinas <catalin.marinas@arm.com>,
Christoph Paasch <cpaasch@apple.com>,
stable@vger.kernel.org, rcu@vger.kernel.org
Subject: Re: [PATCH] rcu: kmemleak: Ignore kmemleak false positives when RCU-freeing objects
Date: Mon, 2 Oct 2023 13:11:31 -0700 [thread overview]
Message-ID: <e715c26a-61b9-4815-8cb6-d18839cd98f5@paulmck-laptop> (raw)
In-Reply-To: <20230930174657.800551-1-joel@joelfernandes.org>
On Sat, Sep 30, 2023 at 05:46:56PM +0000, Joel Fernandes (Google) wrote:
> 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>
> Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Reviewed-by: Paul E. McKenney <paulmck@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 cb1caefa8bd0..24423877962c 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>
> @@ -3388,6 +3389,14 @@ 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);
> --
> 2.42.0.582.g8ccd20d70d-goog
>
prev parent reply other threads:[~2023-10-02 20:11 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-09-30 17:46 [PATCH] rcu: kmemleak: Ignore kmemleak false positives when RCU-freeing objects Joel Fernandes (Google)
2023-10-02 20:11 ` Paul E. McKenney [this message]
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