linux-kernel - [PATCH] cred: Use RCU primitives to access RCU pointers

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Message-Id: <20200128072740.21272-1-frextrite@gmail.com>
Date:   Tue, 28 Jan 2020 12:57:41 +0530
From:   Amol Grover <frextrite@...il.com>
To:     David Howells <dhowells@...hat.com>,
        Shakeel Butt <shakeelb@...gle.com>,
        James Morris <jamorris@...ux.microsoft.com>,
        Oleg Nesterov <oleg@...hat.com>,
        Kees Cook <keescook@...omium.org>,
        Amol Grover <frextrite@...il.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Jann Horn <jannh@...gle.com>
Cc:     linux-kernel@...r.kernel.org,
        linux-kernel-mentees@...ts.linuxfoundation.org,
        Joel Fernandes <joel@...lfernandes.org>,
        Madhuparna Bhowmik <madhuparnabhowmik04@...il.com>,
        "Paul E . McKenney" <paulmck@...nel.org>
Subject: [PATCH] cred: Use RCU primitives to access RCU pointers

task_struct.cred and task_struct.real_cred are annotated by __rcu,
hence use rcu_access_pointer to access them.

Fixes the following sparse errors:
kernel/cred.c:144:9: error: incompatible types in comparison expression
(different address spaces):
kernel/cred.c:144:9:    struct cred *
kernel/cred.c:144:9:    struct cred const [noderef] <asn:4> *
kernel/cred.c:145:9: error: incompatible types in comparison expression
(different address spaces):
kernel/cred.c:145:9:    struct cred *
kernel/cred.c:145:9:    struct cred const [noderef] <asn:4> *

Signed-off-by: Amol Grover <frextrite@...il.com>
---
 kernel/cred.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/kernel/cred.c b/kernel/cred.c
index 809a985b1793..3043c8e1544d 100644
--- a/kernel/cred.c
+++ b/kernel/cred.c
@@ -141,8 +141,8 @@ void __put_cred(struct cred *cred)
 	cred->magic = CRED_MAGIC_DEAD;
 	cred->put_addr = __builtin_return_address(0);
 #endif
-	BUG_ON(cred == current->cred);
-	BUG_ON(cred == current->real_cred);
+	BUG_ON(cred == rcu_access_pointer(current->cred));
+	BUG_ON(cred == rcu_access_pointer(current->real_cred));
 
 	if (cred->non_rcu)
 		put_cred_rcu(&cred->rcu);
-- 
2.24.1