[PATCH 6.1 366/451] RDMA/device: Fix a race between mad_client and cm_client init

Sasha Levin
2024-03-24T23:18:03Z

From: Shifeng Li <lishifeng@sangfor.com.cn>

[ Upstream commit 7a8bccd8b29c321ac181369b42b04fecf05f98e2 ]

The mad_client will be initialized in enable_device_and_get(), while the
devices_rwsem will be downgraded to a read semaphore. There is a window
that leads to the failed initialization for cm_client, since it can not
get matched mad port from ib_mad_port_list, and the matched mad port will
be added to the list after that.

mad_client | cm_client
------------------|--------------------------------------------------------
ib_register_device|
enable_device_and_get
down_write(&devices_rwsem)
xa_set_mark(&devices, DEVICE_REGISTERED)
downgrade_write(&devices_rwsem)
|
|ib_cm_init
|ib_register_client(&cm_client)
|down_read(&devices_rwsem)
|xa_for_each_marked (&devices, DEVICE_REGISTERED)
|add_client_context
|cm_add_one
|ib_register_mad_agent
|ib_get_mad_port
|__ib_get_mad_port
|list_for_each_entry(entry, &ib_mad_port_list, port_list)
|return NULL
|up_read(&devices_rwsem)
|
add_client_context|
ib_mad_init_device|
ib_mad_port_open |
list_add_tail(&port_priv->port_list, &ib_mad_port_list)
up_read(&devices_rwsem)
|

Fix it by using down_write(&devices_rwsem) in ib_register_client().

Fixes: d0899892edd0 ("RDMA/device: Provide APIs from the core code to help unregistration")
Link: https://lore.kernel.org/r/20240203035313.98991-1-lishifeng@sangfor.com.cn
Suggested-by: Jason Gunthorpe <jgg@ziepe.ca>
Signed-off-by: Shifeng Li <lishifeng@sangfor.com.cn>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/infiniband/core/device.c | 37 +++++++++++++++++++-------------
1 file changed, 22 insertions(+), 15 deletions(-)

diff --git a/drivers/infiniband/core/device.c b/drivers/infiniband/core/device.c
index 3a9b9a28d858f..453188db39d83 100644
--- a/drivers/infiniband/core/device.c
+++ b/drivers/infiniband/core/device.c
@@ -1730,7 +1730,7 @@ static int assign_client_id(struct ib_client *client)
{
int ret;

- down_write(&clients_rwsem);
+ lockdep_assert_held(&clients_rwsem);
/*
* The add/remove callbacks must be called in FIFO/LIFO order. To
* achieve this we assign client_ids so they are sorted in
@@ -1739,14 +1739,11 @@ static int assign_client_id(struct ib_client *client)
client->client_id = highest_client_id;
ret = xa_insert(&clients, client->client_id, client, GFP_KERNEL);
if (ret)
- goto out;
+ return ret;

highest_client_id++;
xa_set_mark(&clients, client->client_id, CLIENT_REGISTERED);
-
-out:
- up_write(&clients_rwsem);
- return ret;
+ return 0;
}

static void remove_client_id(struct ib_client *client)
@@ -1776,25 +1773,35 @@ int ib_register_client(struct ib_client *client)
{
struct ib_device *device;
unsigned long index;
+ bool need_unreg = false;
int ret;

refcount_set(&client->uses, 1);
init_completion(&client->uses_zero);
+
+ /*
+ * The devices_rwsem is held in write mode to ensure that a racing
+ * ib_register_device() sees a consisent view of clients and devices.
+ */
+ down_write(&devices_rwsem);
+ down_write(&clients_rwsem);
ret = assign_client_id(client);
if (ret)
- return ret;
+ goto out;

- down_read(&devices_rwsem);
+ need_unreg = true;
xa_for_each_marked (&devices, index, device, DEVICE_REGISTERED) {
ret = add_client_context(device, client);
- if (ret) {
- up_read(&devices_rwsem);
- ib_unregister_client(client);
- return ret;
- }
+ if (ret)
+ goto out;
}
- up_read(&devices_rwsem);
- return 0;
+ ret = 0;
+out:
+ up_write(&clients_rwsem);
+ up_write(&devices_rwsem);
+ if (need_unreg && ret)
+ ib_unregister_client(client);
+ return ret;
}
EXPORT_SYMBOL(ib_register_client);

--
2.43.0