linux-kernel - [PATCH] signal.c: Fix sparse warnings

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Date:   Wed,  5 Feb 2020 22:54:37 +0530
From:   madhuparnabhowmik10@...il.com
To:     ebiederm@...ssion.com, oleg@...hat.com,
        christian.brauner@...ntu.com, guro@...com, tj@...nel.org
Cc:     linux-kernel@...r.kernel.org, paulmck@...nel.org,
        joel@...lfernandes.org,
        linux-kernel-mentees@...ts.linuxfoundation.org,
        frextrite@...il.com,
        Madhuparna Bhowmik <madhuparnabhowmik10@...il.com>
Subject: [PATCH] signal.c: Fix sparse warnings

From: Madhuparna Bhowmik <madhuparnabhowmik10@...il.com>

This patch fixes the following two sparse warnings caused due to
accessing RCU protected pointer tsk->parent without rcu primitives.

kernel/signal.c:1948:65: warning: incorrect type in argument 1 (different address spaces)
kernel/signal.c:1948:65:    expected struct task_struct *tsk
kernel/signal.c:1948:65:    got struct task_struct [noderef] <asn:4> *parent
kernel/signal.c:1949:40: warning: incorrect type in argument 1 (different address spaces)
kernel/signal.c:1949:40:    expected void const volatile *p
kernel/signal.c:1949:40:    got struct cred const [noderef] <asn:4> *[noderef] <asn:4> *
kernel/signal.c:1949:40: warning: incorrect type in argument 1 (different address spaces)
kernel/signal.c:1949:40:    expected void const volatile *p
kernel/signal.c:1949:40:    got struct cred const [noderef] <asn:4> *[noderef] <asn:4> *

Signed-off-by: Madhuparna Bhowmik <madhuparnabhowmik10@...il.com>
---
 kernel/signal.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/kernel/signal.c b/kernel/signal.c
index 9ad8dea93dbb..8227058ea8c4 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -1945,8 +1945,8 @@ bool do_notify_parent(struct task_struct *tsk, int sig)
 	 * correct to rely on this
 	 */
 	rcu_read_lock();
-	info.si_pid = task_pid_nr_ns(tsk, task_active_pid_ns(tsk->parent));
-	info.si_uid = from_kuid_munged(task_cred_xxx(tsk->parent, user_ns),
+	info.si_pid = task_pid_nr_ns(tsk, task_active_pid_ns(rcu_dereference(tsk->parent)));
+	info.si_uid = from_kuid_munged(task_cred_xxx(rcu_dereference(tsk->parent), user_ns),
 				       task_uid(tsk));
 	rcu_read_unlock();
 
-- 
2.17.1