Subject: [net 7/7] net/mlx5: Fix bridge mode operations when there are no VFs

From: Saeed Mahameed <[email-masked]>
Date: Mon, 9 Sep 2024 12:45:05 -0700

From: Benjamin Poirier <[email-masked]>

Currently, trying to set the bridge mode attribute when numvfs=0 leads to a
crash:

bridge link set dev eth2 hwmode vepa

[  168.967392] BUG: kernel NULL pointer dereference, address: 0000000000000030
[...]
[  168.969989] RIP: 0010:mlx5_add_flow_rules+0x1f/0x300 [mlx5_core]
[...]
[  168.976037] Call Trace:
[  168.976188]  <TASK>
[  168.978620]  _mlx5_eswitch_set_vepa_locked+0x113/0x230 [mlx5_core]
[  168.979074]  mlx5_eswitch_set_vepa+0x7f/0xa0 [mlx5_core]
[  168.979471]  rtnl_bridge_setlink+0xe9/0x1f0
[  168.979714]  rtnetlink_rcv_msg+0x159/0x400
[  168.980451]  netlink_rcv_skb+0x54/0x100
[  168.980675]  netlink_unicast+0x241/0x360
[  168.980918]  netlink_sendmsg+0x1f6/0x430
[  168.981162]  ____sys_sendmsg+0x3bb/0x3f0
[  168.982155]  ___sys_sendmsg+0x88/0xd0
[  168.985036]  __sys_sendmsg+0x59/0xa0
[  168.985477]  do_syscall_64+0x79/0x150
[  168.987273]  entry_SYSCALL_64_after_hwframe+0x76/0x7e
[  168.987773] RIP: 0033:0x7f8f7950f917

(esw->fdb_table.legacy.vepa_fdb is null)

The bridge mode is only relevant when there are multiple functions per
port. Therefore, prevent setting and getting this setting when there are no
VFs.

Note that after this change, there are no settings to change on the PF
interface using `bridge link` when there are no VFs, so the interface no
longer appears in the `bridge link` output.

Fixes: 4b89251de024 ("net/mlx5: Support ndo bridge_setlink and getlink")
Signed-off-by: Benjamin Poirier <[email-masked]>
Reviewed-by: Cosmin Ratiu <[email-masked]>
Signed-off-by: Saeed Mahameed <[email-masked]>
---
 drivers/net/ethernet/mellanox/mlx5/core/esw/legacy.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/net/ethernet/mellanox/mlx5/core/esw/legacy.c b/drivers/net/ethernet/mellanox/mlx5/core/esw/legacy.c
index 255bc8b749f9..8587cd572da5 100644
--- a/drivers/net/ethernet/mellanox/mlx5/core/esw/legacy.c
+++ b/drivers/net/ethernet/mellanox/mlx5/core/esw/legacy.c
@@ -319,7 +319,7 @@ int mlx5_eswitch_set_vepa(struct mlx5_eswitch *esw, u8 setting)
 		return -EPERM;
 
 	mutex_lock(&esw->state_lock);
-	if (esw->mode != MLX5_ESWITCH_LEGACY) {
+	if (esw->mode != MLX5_ESWITCH_LEGACY || !mlx5_esw_is_fdb_created(esw)) {
 		err = -EOPNOTSUPP;
 		goto out;
 	}
@@ -339,7 +339,7 @@ int mlx5_eswitch_get_vepa(struct mlx5_eswitch *esw, u8 *setting)
 	if (!mlx5_esw_allowed(esw))
 		return -EPERM;
 
-	if (esw->mode != MLX5_ESWITCH_LEGACY)
+	if (esw->mode != MLX5_ESWITCH_LEGACY || !mlx5_esw_is_fdb_created(esw))
 		return -EOPNOTSUPP;
 
 	*setting = esw->fdb_table.legacy.vepa_uplink_rule ? 1 : 0;
-- 
2.46.0