Linux Ethernet Bridging - Sep 2021 - [Bridge] [PATCH net] net: bridge: mcast: fix vlan port router deadlock

From: Nikolay Aleksandrov <nikolay at nvidia.com>

Before vlan/port mcast router support was added
br_multicast_set_port_router was used only with bh already disabled due
to the bridge port lock, but that is no longer the case and when it is
called to configure a vlan/port mcast router we can deadlock with the
timer, so always disable bh to make sure it can be called from contexts
with both enabled and disabled bh.

Fixes: 2796d846d74a ("net: bridge: vlan: convert mcast router global option
to per-vlan entry")
Signed-off-by: Nikolay Aleksandrov <nikolay at nvidia.com>
---
 net/bridge/br_multicast.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/net/bridge/br_multicast.c b/net/bridge/br_multicast.c
index 9231617a16e4..3523c8c7068f 100644
--- a/net/bridge/br_multicast.c
+++ b/net/bridge/br_multicast.c
@@ -4255,7 +4255,7 @@ int br_multicast_set_port_router(struct
net_bridge_mcast_port *pmctx,
 	bool del = false;
 
 	brmctx = br_multicast_port_ctx_get_global(pmctx);
-	spin_lock(&brmctx->br->multicast_lock);
+	spin_lock_bh(&brmctx->br->multicast_lock);
 	if (pmctx->multicast_router == val) {
 		/* Refresh the temp router port timer */
 		if (pmctx->multicast_router == MDB_RTR_TYPE_TEMP) {
@@ -4305,7 +4305,7 @@ int br_multicast_set_port_router(struct
net_bridge_mcast_port *pmctx,
 	}
 	err = 0;
 unlock:
-	spin_unlock(&brmctx->br->multicast_lock);
+	spin_unlock_bh(&brmctx->br->multicast_lock);
 
 	return err;
 }
-- 
2.31.1

Hello:

This patch was applied to netdev/net.git (refs/heads/master):

On Fri,  3 Sep 2021 12:34:15 +0300 you wrote:
> From: Nikolay Aleksandrov <nikolay at nvidia.com>
> 
> Before vlan/port mcast router support was added
> br_multicast_set_port_router was used only with bh already disabled due
> to the bridge port lock, but that is no longer the case and when it is
> called to configure a vlan/port mcast router we can deadlock with the
> timer, so always disable bh to make sure it can be called from contexts
> with both enabled and disabled bh.
> 
> [...]
Here is the summary with links:
  - [net] net: bridge: mcast: fix vlan port router deadlock
    https://git.kernel.org/netdev/net/c/ddd0d5293810

You are awesome, thank you!
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