Subject: [PATCH 08/20] tcp: fix tcp_fastopen unaligned access complaints on sparc

From: Shannon Nelson <[email-masked]>
Date: Thu, 12 Jan 2017 14:24:58 -0800

[ Upstream commit 003c941057eaa868ca6fedd29a274c863167230d ]

Fix up a data alignment issue on sparc by swapping the order
of the cookie byte array field with the length field in
struct tcp_fastopen_cookie, and making it a proper union
to clean up the typecasting.

This addresses log complaints like these:
    log_unaligned: 113 callbacks suppressed
    Kernel unaligned access at TPC[976490] tcp_try_fastopen+0x2d0/0x360
    Kernel unaligned access at TPC[9764ac] tcp_try_fastopen+0x2ec/0x360
    Kernel unaligned access at TPC[9764c8] tcp_try_fastopen+0x308/0x360
    Kernel unaligned access at TPC[9764e4] tcp_try_fastopen+0x324/0x360
    Kernel unaligned access at TPC[976490] tcp_try_fastopen+0x2d0/0x360

Cc: Eric Dumazet <[email-masked]>
Signed-off-by: Shannon Nelson <[email-masked]>
Acked-by: Eric Dumazet <[email-masked]>
Signed-off-by: David S. Miller <[email-masked]>
---
 include/linux/tcp.h     | 7 ++++++-
 net/ipv4/tcp_fastopen.c | 2 +-
 2 files changed, 7 insertions(+), 2 deletions(-)

diff --git a/include/linux/tcp.h b/include/linux/tcp.h
index b386361..318c246 100644
--- a/include/linux/tcp.h
+++ b/include/linux/tcp.h
@@ -56,8 +56,13 @@ static inline unsigned int tcp_optlen(const struct sk_buff *skb)
 
 /* TCP Fast Open Cookie as stored in memory */
 struct tcp_fastopen_cookie {
+	union {
+		u8	val[TCP_FASTOPEN_COOKIE_MAX];
+#if IS_ENABLED(CONFIG_IPV6)
+		struct in6_addr addr;
+#endif
+	};
 	s8	len;
-	u8	val[TCP_FASTOPEN_COOKIE_MAX];
 	bool	exp;	/* In RFC6994 experimental option format */
 };
 
diff --git a/net/ipv4/tcp_fastopen.c b/net/ipv4/tcp_fastopen.c
index 55be6ac..32489e4 100644
--- a/net/ipv4/tcp_fastopen.c
+++ b/net/ipv4/tcp_fastopen.c
@@ -112,7 +112,7 @@ static bool tcp_fastopen_cookie_gen(struct request_sock *req,
 		struct tcp_fastopen_cookie tmp;
 
 		if (__tcp_fastopen_cookie_gen(&ip6h->saddr, &tmp)) {
-			struct in6_addr *buf = (struct in6_addr *) tmp.val;
+			struct in6_addr *buf = &tmp.addr;
 			int i;
 
 			for (i = 0; i < 4; i++)
-- 
2.4.11