[PATCH] Ensure to use icmpv6_socket in non-preemptive context.

[YOSHIFUJI Hideaki / 吉藤英明 <yoshfuji@xxxxxxxxxxxxxx>]

Hello.

[IPV6] Make sure to use icmpv6_socket in non-preemptive context.

We saw following trace several times:

|BUG: using smp_processor_id() in preemptible [00000001] code: httpd/30137
|caller is icmpv6_send+0x23/0x540
| [<c01ad63b>] smp_processor_id+0x9b/0xb8
| [<c02993e7>] icmpv6_send+0x23/0x540

This is because of icmpv6_socket, which is the only one user of
smp_processor_id() in icmpv6_send(), AFAIK.

Since it should be used in non-preemptive context,
let's defer the dereference after disabling preemption
(by icmpv6_xmit_lock()).

Signed-off-by: YOSHIFUJI Hideaki <yoshfuji@xxxxxxxxxxxxxx>

diff --git a/net/ipv6/icmp.c b/net/ipv6/icmp.c
--- a/net/ipv6/icmp.c
+++ b/net/ipv6/icmp.c
@@ -277,8 +277,8 @@ void icmpv6_send(struct sk_buff *skb, in
 {
        struct inet6_dev *idev = NULL;
        struct ipv6hdr *hdr = skb->nh.ipv6h;
-       struct sock *sk = icmpv6_socket->sk;
-       struct ipv6_pinfo *np = inet6_sk(sk);
+       struct sock *sk;
+       struct ipv6_pinfo *np;
        struct in6_addr *saddr = NULL;
        struct dst_entry *dst;
        struct icmp6hdr tmp_hdr;
@@ -358,6 +358,9 @@ void icmpv6_send(struct sk_buff *skb, in
        if (icmpv6_xmit_lock())
                return;
 
+       sk = icmpv6_socket->sk;
+       np = inet6_sk(sk);
+
        if (!icmpv6_xrlim_allow(sk, type, &fl))
                goto out;
 
@@ -423,9 +426,9 @@ out:
 
 static void icmpv6_echo_reply(struct sk_buff *skb)
 {
-       struct sock *sk = icmpv6_socket->sk;
+       struct sock *sk;
        struct inet6_dev *idev;
-       struct ipv6_pinfo *np = inet6_sk(sk);
+       struct ipv6_pinfo *np;
        struct in6_addr *saddr = NULL;
        struct icmp6hdr *icmph = (struct icmp6hdr *) skb->h.raw;
        struct icmp6hdr tmp_hdr;
@@ -454,6 +457,9 @@ static void icmpv6_echo_reply(struct sk_
        if (icmpv6_xmit_lock())
                return;
 
+       sk = icmpv6_socket->sk;
+       np = inet6_sk(sk);
+
        if (!fl.oif && ipv6_addr_is_multicast(&fl.fl6_dst))
                fl.oif = np->mcast_oif;
 

-- 
YOSHIFUJI Hideaki @ USAGI Project  <yoshfuji@xxxxxxxxxxxxxx>
GPG-FP  : 9022 65EB 1ECF 3AD1 0BDF  80D8 4807 F894 E062 0EEA