5.4-stable review patch. If anyone has any objections, please let me know.
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From: Xin Long lucien.xin@gmail.com
[ Upstream commit 22600596b6756b166fd052d5facb66287e6f0bad ]
After commit 8d7017fd621d ("blackhole_netdev: use blackhole_netdev to invalidate dst entries"), blackhole_netdev was introduced to invalidate dst cache entries on the TX path whenever the cache times out or is flushed.
When two UDP sockets (sk1 and sk2) send messages to the same destination simultaneously, they are using the same dst cache. If the dst cache is invalidated on one path (sk2) while the other (sk1) is still transmitting, sk1 may try to use the invalid dst entry.
CPU1 CPU2
udp_sendmsg(sk1) udp_sendmsg(sk2) udp_send_skb() ip_output() <--- dst timeout or flushed dst_dev_put() ip_finish_output2() ip_neigh_for_gw()
This results in a scenario where ip_neigh_for_gw() returns -EINVAL because blackhole_dev lacks an in_dev, which is needed to initialize the neigh in arp_constructor(). This error is then propagated back to userspace, breaking the UDP application.
The patch fixes this issue by assigning an in_dev to blackhole_dev for IPv4, similar to what was done for IPv6 in commit e5f80fcf869a ("ipv6: give an IPv6 dev to blackhole_netdev"). This ensures that even when the dst entry is invalidated with blackhole_dev, it will not fail to create the neigh entry.
As devinet_init() is called ealier than blackhole_netdev_init() in system booting, it can not assign the in_dev to blackhole_dev in devinet_init(). As Paolo suggested, add a separate late_initcall() in devinet.c to ensure inet_blackhole_dev_init() is called after blackhole_netdev_init().
Fixes: 8d7017fd621d ("blackhole_netdev: use blackhole_netdev to invalidate dst entries") Signed-off-by: Xin Long lucien.xin@gmail.com Reviewed-by: Eric Dumazet edumazet@google.com Link: https://patch.msgid.link/3000792d45ca44e16c785ebe2b092e610e5b3df1.1728499633... Signed-off-by: Jakub Kicinski kuba@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- net/ipv4/devinet.c | 35 +++++++++++++++++++++++++---------- 1 file changed, 25 insertions(+), 10 deletions(-)
diff --git a/net/ipv4/devinet.c b/net/ipv4/devinet.c index dec884bf73f05..9910844c890ba 100644 --- a/net/ipv4/devinet.c +++ b/net/ipv4/devinet.c @@ -273,17 +273,19 @@ static struct in_device *inetdev_init(struct net_device *dev) /* Account for reference dev->ip_ptr (below) */ refcount_set(&in_dev->refcnt, 1);
- err = devinet_sysctl_register(in_dev); - if (err) { - in_dev->dead = 1; - neigh_parms_release(&arp_tbl, in_dev->arp_parms); - in_dev_put(in_dev); - in_dev = NULL; - goto out; + if (dev != blackhole_netdev) { + err = devinet_sysctl_register(in_dev); + if (err) { + in_dev->dead = 1; + neigh_parms_release(&arp_tbl, in_dev->arp_parms); + in_dev_put(in_dev); + in_dev = NULL; + goto out; + } + ip_mc_init_dev(in_dev); + if (dev->flags & IFF_UP) + ip_mc_up(in_dev); } - ip_mc_init_dev(in_dev); - if (dev->flags & IFF_UP) - ip_mc_up(in_dev);
/* we can receive as soon as ip_ptr is set -- do this last */ rcu_assign_pointer(dev->ip_ptr, in_dev); @@ -328,6 +330,19 @@ static void inetdev_destroy(struct in_device *in_dev) call_rcu(&in_dev->rcu_head, in_dev_rcu_put); }
+static int __init inet_blackhole_dev_init(void) +{ + int err = 0; + + rtnl_lock(); + if (!inetdev_init(blackhole_netdev)) + err = -ENOMEM; + rtnl_unlock(); + + return err; +} +late_initcall(inet_blackhole_dev_init); + int inet_addr_onlink(struct in_device *in_dev, __be32 a, __be32 b) { const struct in_ifaddr *ifa;