netdev - [net 1/7] net/mlx5: Fix sleep while atomic in mlx5_eswitch_get

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Date:   Wed, 19 Feb 2020 03:06:23 +0000
From:   Saeed Mahameed <saeedm@...lanox.com>
To:     "David S. Miller" <davem@...emloft.net>,
        "kuba@...nel.org" <kuba@...nel.org>
CC:     "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        Huy Nguyen <huyn@...lanox.com>,
        Mark Bloch <markb@...lanox.com>,
        Saeed Mahameed <saeedm@...lanox.com>
Subject: [net 1/7] net/mlx5: Fix sleep while atomic in mlx5_eswitch_get_vepa

From: Huy Nguyen <huyn@...lanox.com>

rtnl_bridge_getlink is protected by rcu lock, so mlx5_eswitch_get_vepa
cannot take mutex lock. Two possible issues can happen:
1. User at the same time change vepa mode via RTM_SETLINK command.
2. User at the same time change the switchdev mode via devlink netlink
interface.

Case 1 cannot happen because rtnl executes one message in order.
Case 2 can happen but we do not expect user to change the switchdev mode
when changing vepa. Even if a user does it, so he will read a value
which is no longer valid.

Fixes: 8da202b24913 ("net/mlx5: E-Switch, Add support for VEPA in legacy mode.")
Signed-off-by: Huy Nguyen <huyn@...lanox.com>
Reviewed-by: Mark Bloch <markb@...lanox.com>
Signed-off-by: Saeed Mahameed <saeedm@...lanox.com>
---
 drivers/net/ethernet/mellanox/mlx5/core/eswitch.c | 14 +++-----------
 1 file changed, 3 insertions(+), 11 deletions(-)

diff --git a/drivers/net/ethernet/mellanox/mlx5/core/eswitch.c b/drivers/net/ethernet/mellanox/mlx5/core/eswitch.c
index 5acf60b1bbfe..564d42605892 100644
--- a/drivers/net/ethernet/mellanox/mlx5/core/eswitch.c
+++ b/drivers/net/ethernet/mellanox/mlx5/core/eswitch.c
@@ -2452,25 +2452,17 @@ int mlx5_eswitch_set_vepa(struct mlx5_eswitch *esw, u8 setting)
 
 int mlx5_eswitch_get_vepa(struct mlx5_eswitch *esw, u8 *setting)
 {
-	int err = 0;
-
 	if (!esw)
 		return -EOPNOTSUPP;
 
 	if (!ESW_ALLOWED(esw))
 		return -EPERM;
 
-	mutex_lock(&esw->state_lock);
-	if (esw->mode != MLX5_ESWITCH_LEGACY) {
-		err = -EOPNOTSUPP;
-		goto out;
-	}
+	if (esw->mode != MLX5_ESWITCH_LEGACY)
+		return -EOPNOTSUPP;
 
 	*setting = esw->fdb_table.legacy.vepa_uplink_rule ? 1 : 0;
-
-out:
-	mutex_unlock(&esw->state_lock);
-	return err;
+	return 0;
 }
 
 int mlx5_eswitch_set_vport_trust(struct mlx5_eswitch *esw,
-- 
2.24.1