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Message-ID: <20200330233229.GG19865@paulmck-ThinkPad-P72>
Date: Mon, 30 Mar 2020 16:32:29 -0700
From: "Paul E. McKenney" <paulmck@...nel.org>
To: Will Deacon <will@...nel.org>
Cc: linux-kernel@...r.kernel.org, Eric Dumazet <edumazet@...gle.com>,
Jann Horn <jannh@...gle.com>, Kees Cook <keescook@...omium.org>,
Maddie Stone <maddiestone@...gle.com>,
Marco Elver <elver@...gle.com>,
Peter Zijlstra <peterz@...radead.org>,
Thomas Gleixner <tglx@...utronix.de>, kernel-team@...roid.com,
kernel-hardening@...ts.openwall.com
Subject: Re: [RFC PATCH 12/21] list: Poison ->next pointer for non-RCU
deletion of 'hlist_nulls_node'
On Tue, Mar 24, 2020 at 03:36:34PM +0000, Will Deacon wrote:
> hlist_nulls_del() is used for non-RCU deletion of an 'hlist_nulls_node'
> and so we can safely poison the ->next pointer without having to worry
> about concurrent readers, just like we do for other non-RCU list
> deletion primitives
>
> Cc: Paul E. McKenney <paulmck@...nel.org>
> Cc: Peter Zijlstra <peterz@...radead.org>
> Signed-off-by: Will Deacon <will@...nel.org>
Agreed, any code having difficulty with this change should use instead
hlist_nulls_del_rcu().
Reviewed-by: Paul E. McKenney <paulmck@...nel.org>
> ---
> include/linux/list_nulls.h | 1 +
> 1 file changed, 1 insertion(+)
>
> diff --git a/include/linux/list_nulls.h b/include/linux/list_nulls.h
> index fd154ceb5b0d..48f33ae16381 100644
> --- a/include/linux/list_nulls.h
> +++ b/include/linux/list_nulls.h
> @@ -99,6 +99,7 @@ static inline void __hlist_nulls_del(struct hlist_nulls_node *n)
> static inline void hlist_nulls_del(struct hlist_nulls_node *n)
> {
> __hlist_nulls_del(n);
> + n->next = LIST_POISON1;
> n->pprev = LIST_POISON2;
> }
>
> --
> 2.20.1
>
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