From f5d547676ca068e10934687f59ac1e798eaae87a Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Mon, 1 Apr 2019 03:09:20 -0700 Subject: tcp: fix tcp_inet6_sk() for 32bit kernels It turns out that struct ipv6_pinfo is not located as we think. inet6_sk_generic() and tcp_inet6_sk() disagree on 32bit kernels by 4-bytes, because struct tcp_sock has 8-bytes alignment, but ipv6_pinfo size is not a multiple of 8. sizeof(struct ipv6_pinfo): 116 (not padded to 8) I actually first coded tcp_inet6_sk() as this patch does, but thought that "container_of(tcp_sk(sk), struct tcp6_sock, tcp)" was cleaner. As Julian told me : Nobody should use tcp6_sock.inet6 directly, it should be accessed via tcp_inet6_sk() or inet6_sk(). This happened when we added the first u64 field in struct tcp_sock. Fixes: 93a77c11ae79 ("tcp: add tcp_inet6_sk() helper") Signed-off-by: Eric Dumazet Bisected-by: Julian Anastasov Signed-off-by: David S. Miller --- net/ipv6/tcp_ipv6.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) (limited to 'net/ipv6/tcp_ipv6.c') diff --git a/net/ipv6/tcp_ipv6.c b/net/ipv6/tcp_ipv6.c index eec814fe53b8..82018bdce863 100644 --- a/net/ipv6/tcp_ipv6.c +++ b/net/ipv6/tcp_ipv6.c @@ -93,12 +93,13 @@ static struct tcp_md5sig_key *tcp_v6_md5_do_lookup(const struct sock *sk, /* Helper returning the inet6 address from a given tcp socket. * It can be used in TCP stack instead of inet6_sk(sk). * This avoids a dereference and allow compiler optimizations. + * It is a specialized version of inet6_sk_generic(). */ static struct ipv6_pinfo *tcp_inet6_sk(const struct sock *sk) { - struct tcp6_sock *tcp6 = container_of(tcp_sk(sk), struct tcp6_sock, tcp); + unsigned int offset = sizeof(struct tcp6_sock) - sizeof(struct ipv6_pinfo); - return &tcp6->inet6; + return (struct ipv6_pinfo *)(((u8 *)sk) + offset); } static void inet6_sk_rx_dst_set(struct sock *sk, const struct sk_buff *skb) -- cgit v1.2.3