# \[PATCH RDMA v2\] RDMA/rxe: add mutual exclusion in rxe\_net\_del()

- From: Edward Adam Davis \<hidden\>
- Date: 2026-05-16 14:00:28 
- List: netdev
- Page: https://ratatoskr.run/netdev/2026/05/9012967
- Thread: https://ratatoskr.run/linux-rdma/2026/05/6364084/t.md

```text
We must serialize calls to rxe_net_del() or risk a crash as syzbot
reported:

KASAN: null-ptr-deref in range [0x0000000000000020-0x0000000000000027]
Call Trace:
 udp_tunnel_sock_release+0x6d/0x80 net/ipv4/udp_tunnel_core.c:197
 rxe_release_udp_tunnel drivers/infiniband/sw/rxe/rxe_net.c:294 [inline]
 rxe_sock_put drivers/infiniband/sw/rxe/rxe_net.c:639 [inline]
 rxe_net_del+0xfb/0x290 drivers/infiniband/sw/rxe/rxe_net.c:660
 rxe_dellink+0x15/0x20 drivers/infiniband/sw/rxe/rxe.c:254

Jason Gunthorpe suggest placing the lock within rxe to protect its racy
implementation of rxe_net_del(), which looks like it is possibly also
triggered by NETDEV_UNREGISTER.

The patch addressing this issue in nldev_dellink() has already been
applied(0b28000b64f4); however, since the fix has now been relocated
to rxe, the corresponding remedial code in nldev has been removed.

Fixes: f1327abd6abe ("RDMA/rxe: Support RDMA link creation and destruction per net namespace")
Fixes: 0b28000b64f4 ("RDMA/nldev: Add mutual exclusion in nldev_dellink()")
Reported-by: <redacted>
Closes: https://syzkaller.appspot.com/bug?extid=d8f76778263ab65c2b21
Signed-off-by: Edward Adam Davis <redacted>
---
v1 -> v2: serialize calls to rxe net del

 drivers/infiniband/core/nldev.c     | 4 ----
 drivers/infiniband/sw/rxe/rxe_net.c | 7 ++++++-
 2 files changed, 6 insertions(+), 5 deletions(-)

diff --git a/drivers/infiniband/core/nldev.c b/drivers/infiniband/core/nldev.c
index 3cb3cb7629fe..96c745d5bac4 100644
--- a/drivers/infiniband/core/nldev.c
+++ b/drivers/infiniband/core/nldev.c
@@ -1816,8 +1816,6 @@ static int nldev_newlink(struct sk_buff *skb, struct nlmsghdr *nlh,
 	return err;
 }
 
-static DEFINE_MUTEX(nldev_dellink_mutex);
-
 static int nldev_dellink(struct sk_buff *skb, struct nlmsghdr *nlh,
 			  struct netlink_ext_ack *extack)
 {
@@ -1848,9 +1846,7 @@ static int nldev_dellink(struct sk_buff *skb, struct nlmsghdr *nlh,
 	 * implicitly scoped to the driver supporting dynamic link deletion like RXE.
 	 */
 	if (device->link_ops && device->link_ops->dellink) {
-		mutex_lock(&nldev_dellink_mutex);
 		err = device->link_ops->dellink(device);
-		mutex_unlock(&nldev_dellink_mutex);
 		if (err)
 			return err;
 	}
diff --git a/drivers/infiniband/sw/rxe/rxe_net.c b/drivers/infiniband/sw/rxe/rxe_net.c
index 50a2cb5405e2..92847e955ca2 100644
--- a/drivers/infiniband/sw/rxe/rxe_net.c
+++ b/drivers/infiniband/sw/rxe/rxe_net.c
@@ -642,6 +642,8 @@ static void rxe_sock_put(struct sock *sk,
 	}
 }
 
+static DEFINE_MUTEX(rxe_net_del_mutex);
+
 void rxe_net_del(struct ib_device *dev)
 {
 	struct rxe_dev *rxe = container_of(dev, struct rxe_dev, ib_dev);
@@ -649,9 +651,10 @@ void rxe_net_del(struct ib_device *dev)
 	struct sock *sk;
 	struct net *net;
 
+	mutex_lock(&rxe_net_del_mutex);
 	ndev = rxe_ib_device_get_netdev(&rxe->ib_dev);
 	if (!ndev)
-		return;
+		goto out;
 
 	net = dev_net(ndev);
 
@@ -664,6 +667,8 @@ void rxe_net_del(struct ib_device *dev)
 		rxe_sock_put(sk, rxe_ns_pernet_set_sk6, net);
 
 	dev_put(ndev);
+out:
+	mutex_unlock(&rxe_net_del_mutex);
 }
 
 static void rxe_port_event(struct rxe_dev *rxe,
-- 
2.43.0

```