ip: Fix data-races around sysctl_ip_fwd_update_priority.

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

Fixes: 432e05d32892 ("net: ipv4: Control SKB reprioritization after forwarding")
Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/drivers/net/ethernet/mellanox/mlxsw/spectrum_router.c b/drivers/net/ethernet/mellanox/mlxsw/spectrum_router.c
index 0d8a006..868d28f 100644 (file)
--- a/drivers/net/ethernet/mellanox/mlxsw/spectrum_router.c
+++ b/drivers/net/ethernet/mellanox/mlxsw/spectrum_router.c
@@ -10523,13 +10523,14 @@ static int mlxsw_sp_dscp_init(struct mlxsw_sp *mlxsw_sp)
 static int __mlxsw_sp_router_init(struct mlxsw_sp *mlxsw_sp)
 {
        struct net *net = mlxsw_sp_net(mlxsw_sp);
-       bool usp = net->ipv4.sysctl_ip_fwd_update_priority;
        char rgcr_pl[MLXSW_REG_RGCR_LEN];
        u64 max_rifs;
+       bool usp;
 
        if (!MLXSW_CORE_RES_VALID(mlxsw_sp->core, MAX_RIFS))
                return -EIO;
        max_rifs = MLXSW_CORE_RES_GET(mlxsw_sp->core, MAX_RIFS);
+       usp = READ_ONCE(net->ipv4.sysctl_ip_fwd_update_priority);
 
        mlxsw_reg_rgcr_pack(rgcr_pl, true, true);
        mlxsw_reg_rgcr_max_router_interfaces_set(rgcr_pl, max_rifs);

diff --git a/net/ipv4/ip_forward.c b/net/ipv4/ip_forward.c
index e3aa436..e18931a 100644 (file)
--- a/net/ipv4/ip_forward.c
+++ b/net/ipv4/ip_forward.c
@@ -157,7 +157,7 @@ int ip_forward(struct sk_buff *skb)
            !skb_sec_path(skb))
                ip_rt_send_redirect(skb);
 
-       if (net->ipv4.sysctl_ip_fwd_update_priority)
+       if (READ_ONCE(net->ipv4.sysctl_ip_fwd_update_priority))
                skb->priority = rt_tos2priority(iph->tos);
 
        return NF_HOOK(NFPROTO_IPV4, NF_INET_FORWARD,