[PATCH 6.18.y 2/2] svcrdma: Clear sc_cm_id when ADDR_CHANGE replacement fails

[Sasha Levin <sashal@kernel.org>]

From: Chuck Lever <chuck.lever@oracle.com>

[ Upstream commit 01500306e1d50de7ca7a2cdcdfa28ac0523eb747 ]

When svc_rdma_listen_handler() handles RDMA_CM_EVENT_ADDR_CHANGE,
it creates a replacement listener cm_id and returns 1, telling
the CM core to destroy the old one. If the replacement allocation
fails, sc_cm_id still points at the old cm_id that the CM core is
about to destroy. Any subsequent dereference of sc_cm_id --
such as svc_rdma_detach()'s rdma_disconnect() call -- is a
use-after-free.

NULL sc_cm_id on the failure path and guard svc_rdma_detach()'s
rdma_disconnect() call against NULL so that the listener can
be torn down safely when the server shuts down.

Fixes: d1b586e75ec6 ("svcrdma: Handle ADDR_CHANGE CM event properly")
Cc: stable@vger.kernel.org
Acked-by: Jeff Layton <jlayton@kernel.org>
Link: https://patch.msgid.link/20260527-rdma-follow-on-v1-5-1b09bd87b6cd@oracle.com
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
[ added the missing sc_cm_id NULL guard to the existing __svc_rdma_free() cleanup worker. ]
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 net/sunrpc/xprtrdma/svc_rdma_transport.c | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/net/sunrpc/xprtrdma/svc_rdma_transport.c b/net/sunrpc/xprtrdma/svc_rdma_transport.c
index c8d994272f6f0..aa02c47ae5734 100644
--- a/net/sunrpc/xprtrdma/svc_rdma_transport.c
+++ b/net/sunrpc/xprtrdma/svc_rdma_transport.c
@@ -311,6 +311,7 @@ static int svc_rdma_listen_handler(struct rdma_cm_id *cma_id,
 		if (IS_ERR(listen_id)) {
 			pr_err("Listener dead, address change failed for device %s\n",
 				cma_id->device->name);
+			cma_xprt->sc_cm_id = NULL;
 		} else
 			cma_xprt->sc_cm_id = listen_id;
 		return 1;
@@ -610,14 +611,20 @@ static void svc_rdma_detach(struct svc_xprt *xprt)
 	struct svcxprt_rdma *rdma =
 		container_of(xprt, struct svcxprt_rdma, sc_xprt);
 
-	rdma_disconnect(rdma->sc_cm_id);
+	if (rdma->sc_cm_id)
+		rdma_disconnect(rdma->sc_cm_id);
 }
 
 static void __svc_rdma_free(struct work_struct *work)
 {
 	struct svcxprt_rdma *rdma =
 		container_of(work, struct svcxprt_rdma, sc_work);
-	struct ib_device *device = rdma->sc_cm_id->device;
+	struct ib_device *device;
+
+	if (!rdma->sc_cm_id)
+		goto out_free;
+
+	device = rdma->sc_cm_id->device;
 
 	/* This blocks until the Completion Queues are empty */
 	if (rdma->sc_qp && !IS_ERR(rdma->sc_qp))
@@ -648,6 +655,7 @@ static void __svc_rdma_free(struct work_struct *work)
 
 	if (!test_bit(XPT_LISTENER, &rdma->sc_xprt.xpt_flags))
 		rpcrdma_rn_unregister(device, &rdma->sc_rn);
+out_free:
 	kfree(rdma);
 }
 
-- 
2.53.0