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

[tip-bot2 for Will Deacon]

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@xxxxxxxxxx>
AuthorDate:    Mon, 11 May 2020 21:41:39 +01:00
Committer:     Thomas Gleixner <tglx@xxxxxxxxxxxxx>
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 âtls_build_protoâ:
  | ./include/linux/compiler.h:229:30: warning: assignment discards âconstâ qualifier from pointer target type [-Wdiscarded-qualifiers]
  | net/tls/tls_main.c:640:4: note: in expansion of macro âsmp_store_releaseâ
  |   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@xxxxxxxxxx>
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Acked-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Cc: Boris Pismenny <borisp@xxxxxxxxxxxx>
Cc: Aviad Yehezkel <aviadye@xxxxxxxxxxxx>
Cc: John Fastabend <john.fastabend@xxxxxxxxx>
Cc: Daniel Borkmann <daniel@xxxxxxxxxxxxx>
Link: https://lkml.kernel.org/r/20200511204150.27858-8-will@xxxxxxxxxx

---
 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 &&