[PATCH 3.16 349/370] tcp: fix tcp_fastopen unaligned access complaints on sparc

Ben Hutchings
2017-03-10T12:16:01Z

From: Shannon Nelson <shannon.nelson@oracle.com>

[ 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 <eric.dumazet@gmail.com>
Signed-off-by: Shannon Nelson <shannon.nelson@oracle.com>
Acked-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
[bwh: Backported to 3.16: adjust context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
include/linux/tcp.h | 7 ++++++-
net/ipv4/tcp_fastopen.c | 2 +-
2 files changed, 7 insertions(+), 2 deletions(-)

--- a/include/linux/tcp.h
+++ b/include/linux/tcp.h
@@ -57,8 +57,13 @@ static inline unsigned int tcp_optlen(co

/* 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];
};

/* This defines a selective acknowledgement block. */
--- a/net/ipv4/tcp_fastopen.c
+++ b/net/ipv4/tcp_fastopen.c
@@ -112,7 +112,7 @@ static bool tcp_fastopen_cookie_gen(stru
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 = 4;

for (i = 0; i < 4; i++)