From: Nikolay Aleksandrov <nikolay@xxxxxxxxxx>
When dereferencing the port vlan group we should use the rcu helper
instead of the one relying on rtnl. In br_multicast_pg_to_port_ctx the
entry cannot disappear as we hold the multicast lock and rcu as explained
in the comment above it.
For the same reason we're ok in br_multicast_start_querier.
=============================
WARNING: suspicious RCU usage
5.14.0-rc5+ #429 Tainted: G W
-----------------------------
net/bridge/br_private.h:1478 suspicious rcu_dereference_protected() usage!
other info that might help us debug this:
rcu_scheduler_active = 2, debug_locks = 1
3 locks held by swapper/2/0:
#0: ffff88822be85eb0 ((&p->timer)){+.-.}-{0:0}, at: call_timer_fn+0x5/0x2da
#1: ffff88810b32f260 (&br->multicast_lock){+.-.}-{3:3}, at: br_multicast_port_group_expired+0x28/0x13d [bridge]
#2: ffffffff824f6c80 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire.constprop.0+0x0/0x22 [bridge]
stack backtrace:
CPU: 2 PID: 0 Comm: swapper/2 Kdump: loaded Tainted: G W 5.14.0-rc5+ #429
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.14.0-4.fc34 04/01/2014
Call Trace:
<IRQ>
dump_stack_lvl+0x45/0x59
nbp_vlan_group+0x3e/0x44 [bridge]
br_multicast_pg_to_port_ctx+0xd6/0x10d [bridge]
br_multicast_star_g_handle_mode+0xa1/0x2ce [bridge]
? netlink_broadcast+0xf/0x11
? nlmsg_notify+0x56/0x99
? br_mdb_notify+0x224/0x2e9 [bridge]
? br_multicast_del_pg+0x1dc/0x26d [bridge]
br_multicast_del_pg+0x1dc/0x26d [bridge]
br_multicast_port_group_expired+0xaa/0x13d [bridge]
? __grp_src_delete_marked.isra.0+0x35/0x35 [bridge]
? __grp_src_delete_marked.isra.0+0x35/0x35 [bridge]
call_timer_fn+0x134/0x2da
__run_timers+0x169/0x193
run_timer_softirq+0x19/0x2d
__do_softirq+0x1bc/0x42a
__irq_exit_rcu+0x5c/0xb3
irq_exit_rcu+0xa/0x12
sysvec_apic_timer_interrupt+0x5e/0x75
</IRQ>
asm_sysvec_apic_timer_interrupt+0x12/0x20
RIP: 0010:default_idle+0xc/0xd
Code: e8 14 40 71 ff e8 10 b3 ff ff 4c 89 e2 48 89 ef 31 f6 5d 41 5c e9 a9 e8 c2 ff cc cc cc cc 0f 1f 44 00 00 e8 7f 55 65 ff fb f4 <c3> 0f 1f 44 00 00 55 65 48 8b 2c 25 40 6f 01 00 53 f0 80 4d 02 20
RSP: 0018:ffff88810033bf00 EFLAGS: 00000206
RAX: ffffffff819cf828 RBX: ffff888100328000 RCX: 0000000000000001
RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffffffff819cfa2d
RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000001
R10: ffff8881008302c0 R11: 00000000000006db R12: 0000000000000000
R13: 0000000000000002 R14: 0000000000000000 R15: 0000000000000000
? __sched_text_end+0x4/0x4
? default_idle_call+0x15/0x7b
default_idle_call+0x4d/0x7b
do_idle+0x124/0x2a2
cpu_startup_entry+0x1d/0x1f
secondary_startup_64_no_verify+0xb0/0xbb
Fixes: 74edfd483de8 ("net: bridge: multicast: add helper to get port mcast context from port group")
Signed-off-by: Nikolay Aleksandrov <nikolay@xxxxxxxxxx>
---
net/bridge/br_multicast.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)
diff --git a/net/bridge/br_multicast.c b/net/bridge/br_multicast.c
index e411dd814c58..c9f7f56eaf9b 100644
--- a/net/bridge/br_multicast.c
+++ b/net/bridge/br_multicast.c
@@ -221,7 +221,7 @@ br_multicast_pg_to_port_ctx(const struct net_bridge_port_group *pg)
* can safely be used on return
*/
rcu_read_lock();
- vlan = br_vlan_find(nbp_vlan_group(pg->key.port), pg->key.addr.vid);
+ vlan = br_vlan_find(nbp_vlan_group_rcu(pg->key.port), pg->key.addr.vid);
if (vlan && !br_multicast_port_ctx_vlan_disabled(&vlan->port_mcast_ctx))
pmctx = &vlan->port_mcast_ctx;
else
@@ -4329,7 +4329,8 @@ static void br_multicast_start_querier(struct net_bridge_mcast *brmctx,
if (br_multicast_ctx_is_vlan(brmctx)) {
struct net_bridge_vlan *vlan;
- vlan = br_vlan_find(nbp_vlan_group(port), brmctx->vlan->vid);
+ vlan = br_vlan_find(nbp_vlan_group_rcu(port),
+ brmctx->vlan->vid);
if (!vlan ||
br_multicast_port_ctx_state_stopped(&vlan->port_mcast_ctx))
continue;
--
2.31.1
