[PATCH 5.18 019/158] ip: Fix data-races around sysctl_ip_default_ttl.

Greg Kroah-Hartman
2022-07-27T17:31:33Z

From: Kuniyuki Iwashima <kuniyu@amazon.com>

commit 8281b7ec5c56b71cb2cc5a1728b41607be66959c upstream.

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

Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/net/ethernet/netronome/nfp/flower/action.c | 2 +-
include/net/route.h | 2 +-
net/ipv4/ip_sockglue.c | 2 +-
net/ipv4/netfilter/nf_reject_ipv4.c | 4 ++--
net/ipv4/proc.c | 2 +-
net/netfilter/nf_synproxy_core.c | 2 +-
6 files changed, 7 insertions(+), 7 deletions(-)

--- a/drivers/net/ethernet/netronome/nfp/flower/action.c
+++ b/drivers/net/ethernet/netronome/nfp/flower/action.c
@@ -473,7 +473,7 @@ nfp_fl_set_tun(struct nfp_app *app, stru
set_tun->ttl = ip4_dst_hoplimit(&rt->dst);
ip_rt_put(rt);
} else {
- set_tun->ttl = net->ipv4.sysctl_ip_default_ttl;
+ set_tun->ttl = READ_ONCE(net->ipv4.sysctl_ip_default_ttl);
}
}

--- a/include/net/route.h
+++ b/include/net/route.h
@@ -361,7 +361,7 @@ static inline int ip4_dst_hoplimit(const
struct net *net = dev_net(dst->dev);

if (hoplimit == 0)
- hoplimit = net->ipv4.sysctl_ip_default_ttl;
+ hoplimit = READ_ONCE(net->ipv4.sysctl_ip_default_ttl);
return hoplimit;
}

--- a/net/ipv4/ip_sockglue.c
+++ b/net/ipv4/ip_sockglue.c
@@ -1606,7 +1606,7 @@ static int do_ip_getsockopt(struct sock
{
struct net *net = sock_net(sk);
val = (inet->uc_ttl == -1 ?
- net->ipv4.sysctl_ip_default_ttl :
+ READ_ONCE(net->ipv4.sysctl_ip_default_ttl) :
inet->uc_ttl);
break;
}
--- a/net/ipv4/netfilter/nf_reject_ipv4.c
+++ b/net/ipv4/netfilter/nf_reject_ipv4.c
@@ -62,7 +62,7 @@ struct sk_buff *nf_reject_skb_v4_tcp_res

skb_reserve(nskb, LL_MAX_HEADER);
niph = nf_reject_iphdr_put(nskb, oldskb, IPPROTO_TCP,
- net->ipv4.sysctl_ip_default_ttl);
+ READ_ONCE(net->ipv4.sysctl_ip_default_ttl));
nf_reject_ip_tcphdr_put(nskb, oldskb, oth);
niph->tot_len = htons(nskb->len);
ip_send_check(niph);
@@ -115,7 +115,7 @@ struct sk_buff *nf_reject_skb_v4_unreach

skb_reserve(nskb, LL_MAX_HEADER);
niph = nf_reject_iphdr_put(nskb, oldskb, IPPROTO_ICMP,
- net->ipv4.sysctl_ip_default_ttl);
+ READ_ONCE(net->ipv4.sysctl_ip_default_ttl));

skb_reset_transport_header(nskb);
icmph = skb_put_zero(nskb, sizeof(struct icmphdr));
--- a/net/ipv4/proc.c
+++ b/net/ipv4/proc.c
@@ -387,7 +387,7 @@ static int snmp_seq_show_ipstats(struct

seq_printf(seq, "\nIp: %d %d",
IPV4_DEVCONF_ALL(net, FORWARDING) ? 1 : 2,
- net->ipv4.sysctl_ip_default_ttl);
+ READ_ONCE(net->ipv4.sysctl_ip_default_ttl));

BUILD_BUG_ON(offsetof(struct ipstats_mib, mibs) != 0);
snmp_get_cpu_field64_batch(buff64, snmp4_ipstats_list,
--- a/net/netfilter/nf_synproxy_core.c
+++ b/net/netfilter/nf_synproxy_core.c
@@ -405,7 +405,7 @@ synproxy_build_ip(struct net *net, struc
iph->tos = 0;
iph->id = 0;
iph->frag_off = htons(IP_DF);
- iph->ttl = net->ipv4.sysctl_ip_default_ttl;
+ iph->ttl = READ_ONCE(net->ipv4.sysctl_ip_default_ttl);
iph->protocol = IPPROTO_TCP;
iph->check = 0;
iph->saddr = saddr;