linux-kernel - [tip: locking/kcsan] net: tls: Avoid assigning 'const' pointer to non-const pointer

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Message-ID: <158929421795.390.9166692393121757241.tip-bot2@tip-bot2>
Date:   Tue, 12 May 2020 14:36:57 -0000
From:   "tip-bot2 for Will Deacon" <tip-bot2@...utronix.de>
To:     linux-tip-commits@...r.kernel.org
Cc:     Will Deacon <will@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        "Peter Zijlstra (Intel)" <peterz@...radead.org>,
        Boris Pismenny <borisp@...lanox.com>,
        Aviad Yehezkel <aviadye@...lanox.com>,
        John Fastabend <john.fastabend@...il.com>,
        Daniel Borkmann <daniel@...earbox.net>, x86 <x86@...nel.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: [tip: locking/kcsan] net: tls: Avoid assigning 'const' pointer to
 non-const pointer

The following commit has been merged into the locking/kcsan branch of tip:

Commit-ID:     268c779f206f105c12fa82499fbbf960b256750f
Gitweb:        https://git.kernel.org/tip/268c779f206f105c12fa82499fbbf960b256750f
Author:        Will Deacon <will@...nel.org>
AuthorDate:    Mon, 11 May 2020 21:41:39 +01:00
Committer:     Thomas Gleixner <tglx@...utronix.de>
CommitterDate: Tue, 12 May 2020 11:04:12 +02:00

net: tls: Avoid assigning 'const' pointer to non-const pointer

tls_build_proto() uses WRITE_ONCE() to assign a 'const' pointer to a
'non-const' pointer. Cleanups to the implementation of WRITE_ONCE() mean
that this will give rise to a compiler warning, just like a plain old
assignment would do:

  | net/tls/tls_main.c: In function ‘tls_build_proto’:
  | ./include/linux/compiler.h:229:30: warning: assignment discards ‘const’ qualifier from pointer target type [-Wdiscarded-qualifiers]
  | net/tls/tls_main.c:640:4: note: in expansion of macro ‘smp_store_release’
  |   640 |    smp_store_release(&saved_tcpv6_prot, prot);
  |       |    ^~~~~~~~~~~~~~~~~

Drop the const qualifier from the local 'prot' variable, as it isn't
needed.

Signed-off-by: Will Deacon <will@...nel.org>
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
Acked-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Cc: Boris Pismenny <borisp@...lanox.com>
Cc: Aviad Yehezkel <aviadye@...lanox.com>
Cc: John Fastabend <john.fastabend@...il.com>
Cc: Daniel Borkmann <daniel@...earbox.net>
Link: https://lkml.kernel.org/r/20200511204150.27858-8-will@kernel.org

---
 net/tls/tls_main.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/tls/tls_main.c b/net/tls/tls_main.c
index 156efce..b33e11c 100644
--- a/net/tls/tls_main.c
+++ b/net/tls/tls_main.c
@@ -629,7 +629,7 @@ struct tls_context *tls_ctx_create(struct sock *sk)
 static void tls_build_proto(struct sock *sk)
 {
 	int ip_ver = sk->sk_family == AF_INET6 ? TLSV6 : TLSV4;
-	const struct proto *prot = READ_ONCE(sk->sk_prot);
+	struct proto *prot = READ_ONCE(sk->sk_prot);
 
 	/* Build IPv6 TLS whenever the address of tcpv6 _prot changes */
 	if (ip_ver == TLSV6 &&