[patch net-next] devlink: don't take instance lock for nested handle put

Jiri Pirko
2023-10-03T07:43:56Z

From: Jiri Pirko <jiri@nvidia.com>

Lockdep reports following issue:

WARNING: possible circular locking dependency detected
------------------------------------------------------
devlink/8191 is trying to acquire lock:
ffff88813f32c250 (&devlink->lock_key#14){+.+.}-{3:3}, at: devlink_rel_devlink_handle_put+0x11e/0x2d0

but task is already holding lock:
ffffffff8511eca8 (rtnl_mutex){+.+.}-{3:3}, at: unregister_netdev+0xe/0x20

which lock already depends on the new lock.

the existing dependency chain (in reverse order) is:

-> #3 (rtnl_mutex){+.+.}-{3:3}:
lock_acquire+0x1c3/0x500
__mutex_lock+0x14c/0x1b20
register_netdevice_notifier_net+0x13/0x30
mlx5_lag_add_mdev+0x51c/0xa00 [mlx5_core]
mlx5_load+0x222/0xc70 [mlx5_core]
mlx5_init_one_devl_locked+0x4a0/0x1310 [mlx5_core]
mlx5_init_one+0x3b/0x60 [mlx5_core]
probe_one+0x786/0xd00 [mlx5_core]
local_pci_probe+0xd7/0x180
pci_device_probe+0x231/0x720
really_probe+0x1e4/0xb60
__driver_probe_device+0x261/0x470
driver_probe_device+0x49/0x130
__driver_attach+0x215/0x4c0
bus_for_each_dev+0xf0/0x170
bus_add_driver+0x21d/0x590
driver_register+0x133/0x460
vdpa_match_remove+0x89/0xc0 [vdpa]
do_one_initcall+0xc4/0x360
do_init_module+0x22d/0x760
load_module+0x51d7/0x6750
init_module_from_file+0xd2/0x130
idempotent_init_module+0x326/0x5a0
__x64_sys_finit_module+0xc1/0x130
do_syscall_64+0x3d/0x90
entry_SYSCALL_64_after_hwframe+0x46/0xb0

-> #2 (mlx5_intf_mutex){+.+.}-{3:3}:
lock_acquire+0x1c3/0x500
__mutex_lock+0x14c/0x1b20
mlx5_register_device+0x3e/0xd0 [mlx5_core]
mlx5_init_one_devl_locked+0x8fa/0x1310 [mlx5_core]
mlx5_devlink_reload_up+0x147/0x170 [mlx5_core]
devlink_reload+0x203/0x380
devlink_nl_cmd_reload+0xb84/0x10e0
genl_family_rcv_msg_doit+0x1cc/0x2a0
genl_rcv_msg+0x3c9/0x670
netlink_rcv_skb+0x12c/0x360
genl_rcv+0x24/0x40
netlink_unicast+0x435/0x6f0
netlink_sendmsg+0x7a0/0xc70
sock_sendmsg+0xc5/0x190
__sys_sendto+0x1c8/0x290
__x64_sys_sendto+0xdc/0x1b0
do_syscall_64+0x3d/0x90
entry_SYSCALL_64_after_hwframe+0x46/0xb0

-> #1 (&dev->lock_key#8){+.+.}-{3:3}:
lock_acquire+0x1c3/0x500
__mutex_lock+0x14c/0x1b20
mlx5_init_one_devl_locked+0x45/0x1310 [mlx5_core]
mlx5_devlink_reload_up+0x147/0x170 [mlx5_core]
devlink_reload+0x203/0x380
devlink_nl_cmd_reload+0xb84/0x10e0
genl_family_rcv_msg_doit+0x1cc/0x2a0
genl_rcv_msg+0x3c9/0x670
netlink_rcv_skb+0x12c/0x360
genl_rcv+0x24/0x40
netlink_unicast+0x435/0x6f0
netlink_sendmsg+0x7a0/0xc70
sock_sendmsg+0xc5/0x190
__sys_sendto+0x1c8/0x290
__x64_sys_sendto+0xdc/0x1b0
do_syscall_64+0x3d/0x90
entry_SYSCALL_64_after_hwframe+0x46/0xb0

-> #0 (&devlink->lock_key#14){+.+.}-{3:3}:
check_prev_add+0x1af/0x2300
__lock_acquire+0x31d7/0x4eb0
lock_acquire+0x1c3/0x500
__mutex_lock+0x14c/0x1b20
devlink_rel_devlink_handle_put+0x11e/0x2d0
devlink_nl_port_fill+0xddf/0x1b00
devlink_port_notify+0xb5/0x220
__devlink_port_type_set+0x151/0x510
devlink_port_netdevice_event+0x17c/0x220
notifier_call_chain+0x97/0x240
unregister_netdevice_many_notify+0x876/0x1790
unregister_netdevice_queue+0x274/0x350
unregister_netdev+0x18/0x20
mlx5e_vport_rep_unload+0xc5/0x1c0 [mlx5_core]
__esw_offloads_unload_rep+0xd8/0x130 [mlx5_core]
mlx5_esw_offloads_rep_unload+0x52/0x70 [mlx5_core]
mlx5_esw_offloads_unload_rep+0x85/0xc0 [mlx5_core]
mlx5_eswitch_unload_sf_vport+0x41/0x90 [mlx5_core]
mlx5_devlink_sf_port_del+0x120/0x280 [mlx5_core]
genl_family_rcv_msg_doit+0x1cc/0x2a0
genl_rcv_msg+0x3c9/0x670
netlink_rcv_skb+0x12c/0x360
genl_rcv+0x24/0x40
netlink_unicast+0x435/0x6f0
netlink_sendmsg+0x7a0/0xc70
sock_sendmsg+0xc5/0x190
__sys_sendto+0x1c8/0x290
__x64_sys_sendto+0xdc/0x1b0
do_syscall_64+0x3d/0x90
entry_SYSCALL_64_after_hwframe+0x46/0xb0

other info that might help us debug this:

Chain exists of:
&devlink->lock_key#14 --> mlx5_intf_mutex --> rtnl_mutex

Possible unsafe locking scenario:

CPU0 CPU1
---- ----
lock(rtnl_mutex);
lock(mlx5_intf_mutex);
lock(rtnl_mutex);
lock(&devlink->lock_key#14);

Problem is taking the devlink instance lock of nested instance when RTNL
is already held.

To fix this, don't take the devlink instance lock when putting nested
handle. Instead, rely on devlink reference to access relevant pointers
within devlink structure. Also, make sure that the device does
not disappear by taking a reference in devlink_alloc_ns().

Fixes: c137743bce02 ("devlink: introduce object and nested devlink relationship infra")
Signed-off-by: Jiri Pirko <jiri@nvidia.com>
---
net/devlink/core.c | 20 +++++---------------
net/devlink/netlink.c | 6 +++---
2 files changed, 8 insertions(+), 18 deletions(-)

diff --git a/net/devlink/core.c b/net/devlink/core.c
index bcbbb952569f..655903ddbdfd 100644
--- a/net/devlink/core.c
+++ b/net/devlink/core.c
@@ -183,9 +183,8 @@ static struct devlink_rel *devlink_rel_find(unsigned long rel_index)
DEVLINK_REL_IN_USE);
}

-static struct devlink *devlink_rel_devlink_get_lock(u32 rel_index)
+static struct devlink *devlink_rel_devlink_get(u32 rel_index)
{
- struct devlink *devlink;
struct devlink_rel *rel;
u32 devlink_index;

@@ -198,16 +197,7 @@ static struct devlink *devlink_rel_devlink_get_lock(u32 rel_index)
xa_unlock(&devlink_rels);
if (!rel)
return NULL;
- devlink = devlinks_xa_get(devlink_index);
- if (!devlink)
- return NULL;
- devl_lock(devlink);
- if (!devl_is_registered(devlink)) {
- devl_unlock(devlink);
- devlink_put(devlink);
- return NULL;
- }
- return devlink;
+ return devlinks_xa_get(devlink_index);
}

int devlink_rel_devlink_handle_put(struct sk_buff *msg, struct devlink *devlink,
@@ -218,11 +208,10 @@ int devlink_rel_devlink_handle_put(struct sk_buff *msg, struct devlink *devlink,
struct devlink *rel_devlink;
int err;

- rel_devlink = devlink_rel_devlink_get_lock(rel_index);
+ rel_devlink = devlink_rel_devlink_get(rel_index);
if (!rel_devlink)
return 0;
err = devlink_nl_put_nested_handle(msg, net, rel_devlink, attrtype);
- devl_unlock(rel_devlink);
devlink_put(rel_devlink);
if (!err && msg_updated)
*msg_updated = true;
@@ -310,6 +299,7 @@ static void devlink_release(struct work_struct *work)

mutex_destroy(&devlink->lock);
lockdep_unregister_key(&devlink->lock_key);
+ put_device(devlink->dev);
kfree(devlink);
}

@@ -425,7 +415,7 @@ struct devlink *devlink_alloc_ns(const struct devlink_ops *ops,
if (ret < 0)
goto err_xa_alloc;

- devlink->dev = dev;
+ devlink->dev = get_device(dev);
devlink->ops = ops;
xa_init_flags(&devlink->ports, XA_FLAGS_ALLOC);
xa_init_flags(&devlink->params, XA_FLAGS_ALLOC);
diff --git a/net/devlink/netlink.c b/net/devlink/netlink.c
index 499304d9de49..2685c8fcf124 100644
--- a/net/devlink/netlink.c
+++ b/net/devlink/netlink.c
@@ -85,6 +85,7 @@ static const struct nla_policy devlink_nl_policy[DEVLINK_ATTR_MAX + 1] = {
int devlink_nl_put_nested_handle(struct sk_buff *msg, struct net *net,
struct devlink *devlink, int attrtype)
{
+ struct net *devl_net = devlink_net(devlink);
struct nlattr *nested_attr;

nested_attr = nla_nest_start(msg, attrtype);
@@ -92,9 +93,8 @@ int devlink_nl_put_nested_handle(struct sk_buff *msg, struct net *net,
return -EMSGSIZE;
if (devlink_nl_put_handle(msg, devlink))
goto nla_put_failure;
- if (!net_eq(net, devlink_net(devlink))) {
- int id = peernet2id_alloc(net, devlink_net(devlink),
- GFP_KERNEL);
+ if (!net_eq(net, devl_net)) {
+ int id = peernet2id_alloc(net, devl_net, GFP_KERNEL);

if (nla_put_s32(msg, DEVLINK_ATTR_NETNS_ID, id))
return -EMSGSIZE;
--
2.41.0