icmp: Fix a data-race around sysctl_icmp_echo_ignore_all.

While reading sysctl_icmp_echo_ignore_all, it can be changed concurrently.
Thus, we need to add READ_ONCE() to its reader.

Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/ipv4/icmp.c b/net/ipv4/icmp.c
index 0f9e61d..1df4aae 100644 (file)
--- a/net/ipv4/icmp.c
+++ b/net/ipv4/icmp.c
@@ -993,7 +993,7 @@ static enum skb_drop_reason icmp_echo(struct sk_buff *skb)
 
        net = dev_net(skb_dst(skb)->dev);
        /* should there be an ICMP stat for ignored echos? */
-       if (net->ipv4.sysctl_icmp_echo_ignore_all)
+       if (READ_ONCE(net->ipv4.sysctl_icmp_echo_ignore_all))
                return SKB_NOT_DROPPED_YET;
 
        icmp_param.data.icmph      = *icmp_hdr(skb);

diff --git a/net/ipv4/sysctl_net_ipv4.c b/net/ipv4/sysctl_net_ipv4.c
index cd448cd..64682a0 100644 (file)
--- a/net/ipv4/sysctl_net_ipv4.c
+++ b/net/ipv4/sysctl_net_ipv4.c
@@ -599,6 +599,8 @@ static struct ctl_table ipv4_net_table[] = {
                .maxlen         = sizeof(u8),
                .mode           = 0644,
                .proc_handler   = proc_dou8vec_minmax,
+               .extra1         = SYSCTL_ZERO,
+               .extra2         = SYSCTL_ONE
        },
        {
                .procname       = "icmp_echo_enable_probe",