[PATCH 5.10 030/105] ip: Fix data-races around sysctl_ip_fwd_update_priority.

Greg Kroah-Hartman
2022-07-27T16:50:45Z

From: Kuniyuki Iwashima <kuniyu@amazon.com>

[ Upstream commit 7bf9e18d9a5e99e3c83482973557e9f047b051e7 ]

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>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/net/ethernet/mellanox/mlxsw/spectrum_router.c | 3 ++-
net/ipv4/ip_forward.c | 2 +-
2 files changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/net/ethernet/mellanox/mlxsw/spectrum_router.c b/drivers/net/ethernet/mellanox/mlxsw/spectrum_router.c
index 5f143ca16c01..d2887ae508bb 100644
--- a/drivers/net/ethernet/mellanox/mlxsw/spectrum_router.c
+++ b/drivers/net/ethernet/mellanox/mlxsw/spectrum_router.c
@@ -8038,13 +8038,14 @@ 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 00ec819f949b..29730edda220 100644
--- a/net/ipv4/ip_forward.c
+++ b/net/ipv4/ip_forward.c
@@ -151,7 +151,7 @@ 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,
--
2.35.1