linux-kernel - [RFC PATCH 12/21] list: Poison ->next pointer for non-RCU deletion of 'hlist_nulls

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Message-Id: <20200324153643.15527-13-will@kernel.org>
Date:   Tue, 24 Mar 2020 15:36:34 +0000
From:   Will Deacon <will@...nel.org>
To:     linux-kernel@...r.kernel.org
Cc:     Will Deacon <will@...nel.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>,
        "Paul E . McKenney" <paulmck@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Thomas Gleixner <tglx@...utronix.de>, kernel-team@...roid.com,
        kernel-hardening@...ts.openwall.com
Subject: [RFC PATCH 12/21] list: Poison ->next pointer for non-RCU deletion of 'hlist_nulls_node'

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>
---
 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