[PATCH 4.9 49/75] net/mlx5e: Fix possible deadlock of VXLAN lock

Greg Kroah-Hartman
2018-01-01T14:35:46Z

From: Gal Pressman <galp@mellanox.com>

[ Upstream commit 6323514116404cc651df1b7fffa1311ddf8ce647 ]

mlx5e_vxlan_lookup_port is called both from mlx5e_add_vxlan_port (user
context) and mlx5e_features_check (softirq), but the lock acquired does
not disable bottom half and might result in deadlock. Fix it by simply
replacing spin_lock() with spin_lock_bh().
While at it, replace all unnecessary spin_lock_irq() to spin_lock_bh().

lockdep's WARNING: inconsistent lock state
[ 654.028136] inconsistent {SOFTIRQ-ON-W} -> {IN-SOFTIRQ-W} usage.
[ 654.028229] swapper/5/0 [HC0[0]:SC1[9]:HE1:SE0] takes:
[ 654.028321] (&(&vxlan_db->lock)->rlock){+.?.}, at: [<ffffffffa06e7f0e>] mlx5e_vxlan_lookup_port+0x1e/0x50 [mlx5_core]
[ 654.028528] {SOFTIRQ-ON-W} state was registered at:
[ 654.028607] _raw_spin_lock+0x3c/0x70
[ 654.028689] mlx5e_vxlan_lookup_port+0x1e/0x50 [mlx5_core]
[ 654.028794] mlx5e_vxlan_add_port+0x2e/0x120 [mlx5_core]
[ 654.028878] process_one_work+0x1e9/0x640
[ 654.028942] worker_thread+0x4a/0x3f0
[ 654.029002] kthread+0x141/0x180
[ 654.029056] ret_from_fork+0x24/0x30
[ 654.029114] irq event stamp: 579088
[ 654.029174] hardirqs last enabled at (579088): [<ffffffff818f475a>] ip6_finish_output2+0x49a/0x8c0
[ 654.029309] hardirqs last disabled at (579087): [<ffffffff818f470e>] ip6_finish_output2+0x44e/0x8c0
[ 654.029446] softirqs last enabled at (579030): [<ffffffff810b3b3d>] irq_enter+0x6d/0x80
[ 654.029567] softirqs last disabled at (579031): [<ffffffff810b3c05>] irq_exit+0xb5/0xc0
[ 654.029684] other info that might help us debug this:
[ 654.029781] Possible unsafe locking scenario:

[ 654.029868] CPU0
[ 654.029908] ----
[ 654.029947] lock(&(&vxlan_db->lock)->rlock);
[ 654.030045] <Interrupt>
[ 654.030090] lock(&(&vxlan_db->lock)->rlock);
[ 654.030162]
*** DEADLOCK ***

Fixes: b3f63c3d5e2c ("net/mlx5e: Add netdev support for VXLAN tunneling")
Signed-off-by: Gal Pressman <galp@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/net/ethernet/mellanox/mlx5/core/vxlan.c | 20 ++++++++++----------
1 file changed, 10 insertions(+), 10 deletions(-)

--- a/drivers/net/ethernet/mellanox/mlx5/core/vxlan.c
+++ b/drivers/net/ethernet/mellanox/mlx5/core/vxlan.c
@@ -71,9 +71,9 @@ struct mlx5e_vxlan *mlx5e_vxlan_lookup_p
struct mlx5e_vxlan_db *vxlan_db = &priv->vxlan;
struct mlx5e_vxlan *vxlan;

- spin_lock(&vxlan_db->lock);
+ spin_lock_bh(&vxlan_db->lock);
vxlan = radix_tree_lookup(&vxlan_db->tree, port);
- spin_unlock(&vxlan_db->lock);
+ spin_unlock_bh(&vxlan_db->lock);

return vxlan;
}
@@ -100,9 +100,9 @@ static void mlx5e_vxlan_add_port(struct

vxlan->udp_port = port;

- spin_lock_irq(&vxlan_db->lock);
+ spin_lock_bh(&vxlan_db->lock);
err = radix_tree_insert(&vxlan_db->tree, vxlan->udp_port, vxlan);
- spin_unlock_irq(&vxlan_db->lock);
+ spin_unlock_bh(&vxlan_db->lock);
if (err)
goto err_free;

@@ -121,9 +121,9 @@ static void __mlx5e_vxlan_core_del_port(
struct mlx5e_vxlan_db *vxlan_db = &priv->vxlan;
struct mlx5e_vxlan *vxlan;

- spin_lock_irq(&vxlan_db->lock);
+ spin_lock_bh(&vxlan_db->lock);
vxlan = radix_tree_delete(&vxlan_db->tree, port);
- spin_unlock_irq(&vxlan_db->lock);
+ spin_unlock_bh(&vxlan_db->lock);

if (!vxlan)
return;
@@ -171,12 +171,12 @@ void mlx5e_vxlan_cleanup(struct mlx5e_pr
struct mlx5e_vxlan *vxlan;
unsigned int port = 0;

- spin_lock_irq(&vxlan_db->lock);
+ spin_lock_bh(&vxlan_db->lock);
while (radix_tree_gang_lookup(&vxlan_db->tree, (void **)&vxlan, port, 1)) {
port = vxlan->udp_port;
- spin_unlock_irq(&vxlan_db->lock);
+ spin_unlock_bh(&vxlan_db->lock);
__mlx5e_vxlan_core_del_port(priv, (u16)port);
- spin_lock_irq(&vxlan_db->lock);
+ spin_lock_bh(&vxlan_db->lock);
}
- spin_unlock_irq(&vxlan_db->lock);
+ spin_unlock_bh(&vxlan_db->lock);
}