5.15-stable review patch. If anyone has any objections, please let me know.
------------------
From: Paolo Abeni pabeni@redhat.com
[ Upstream commit eb02688c5c45c3e7af7e71f036a7144f5639cbfe ]
The CI is hitting some aperiodic hangup at device removal time in the pmtu.sh self-test:
unregister_netdevice: waiting for veth_A-R1 to become free. Usage count = 6 ref_tracker: veth_A-R1@ffff888013df15d8 has 1/5 users at dst_init+0x84/0x4a0 dst_alloc+0x97/0x150 ip6_dst_alloc+0x23/0x90 ip6_rt_pcpu_alloc+0x1e6/0x520 ip6_pol_route+0x56f/0x840 fib6_rule_lookup+0x334/0x630 ip6_route_output_flags+0x259/0x480 ip6_dst_lookup_tail.constprop.0+0x5c2/0x940 ip6_dst_lookup_flow+0x88/0x190 udp_tunnel6_dst_lookup+0x2a7/0x4c0 vxlan_xmit_one+0xbde/0x4a50 [vxlan] vxlan_xmit+0x9ad/0xf20 [vxlan] dev_hard_start_xmit+0x10e/0x360 __dev_queue_xmit+0xf95/0x18c0 arp_solicit+0x4a2/0xe00 neigh_probe+0xaa/0xf0
While the first suspect is the dst_cache, explicitly tracking the dst owing the last device reference via probes proved such dst is held by the nexthop in the originating fib6_info.
Similar to commit f5b51fe804ec ("ipv6: route: purge exception on removal"), we need to explicitly release the originating fib info when disconnecting a to-be-removed device from a live ipv6 dst: move the fib6_info cleanup into ip6_dst_ifdown().
Tested running:
./pmtu.sh cleanup_ipv6_exception
in a tight loop for more than 400 iterations with no spat, running an unpatched kernel I observed a splat every ~10 iterations.
Fixes: f88d8ea67fbd ("ipv6: Plumb support for nexthop object in a fib6_info") Signed-off-by: Paolo Abeni pabeni@redhat.com Reviewed-by: Eric Dumazet edumazet@google.com Reviewed-by: David Ahern dsahern@kernel.org Link: https://patch.msgid.link/604c45c188c609b732286b47ac2a451a40f6cf6d.1730828007... Signed-off-by: Jakub Kicinski kuba@kernel.org (cherry picked from commit eb02688c5c45c3e7af7e71f036a7144f5639cbfe) [Harshit: Resolved conflict due to missing commit: e5f80fcf869a ("ipv6: give an IPv6 dev to blackhole_netdev") and commit: b4cb4a1391dc ("net: use unrcu_pointer() helper") in linux-5.15.y] Signed-off-by: Harshit Mogalapalli harshit.m.mogalapalli@oracle.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- net/ipv6/route.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-)
--- a/net/ipv6/route.c +++ b/net/ipv6/route.c @@ -377,6 +377,7 @@ static void ip6_dst_ifdown(struct dst_en struct inet6_dev *idev = rt->rt6i_idev; struct net_device *loopback_dev = dev_net(dev)->loopback_dev; + struct fib6_info *from;
if (idev && idev->dev != loopback_dev) { struct inet6_dev *loopback_idev = in6_dev_get(loopback_dev); @@ -385,6 +386,8 @@ static void ip6_dst_ifdown(struct dst_en in6_dev_put(idev); } } + from = xchg((__force struct fib6_info **)&rt->from, NULL); + fib6_info_release(from); }
static bool __rt6_check_expired(const struct rt6_info *rt) @@ -1443,7 +1446,6 @@ static DEFINE_SPINLOCK(rt6_exception_loc static void rt6_remove_exception(struct rt6_exception_bucket *bucket, struct rt6_exception *rt6_ex) { - struct fib6_info *from; struct net *net;
if (!bucket || !rt6_ex) @@ -1455,8 +1457,6 @@ static void rt6_remove_exception(struct /* purge completely the exception to allow releasing the held resources: * some [sk] cache may keep the dst around for unlimited time */ - from = xchg((__force struct fib6_info **)&rt6_ex->rt6i->from, NULL); - fib6_info_release(from); dst_dev_put(&rt6_ex->rt6i->dst);
hlist_del_rcu(&rt6_ex->hlist);