[PATCH 2/8] xprtrdma: Initialize re_id before removal registration

From: Chris Mason <[email protected]>

rpcrdma_create_id() registers ep->re_rn with the rpcrdma ib_client
before returning the new rdma_cm_id to rpcrdma_ep_create(). However
rpcrdma_ep_create() currently stores that pointer in ep->re_id only
after rpcrdma_create_id() returns.

A local administrator can race an NFS/RDMA mount against RDMA device
removal. If rpcrdma_remove_one() observes the just-registered
notification before rpcrdma_ep_create() assigns ep->re_id,
rpcrdma_ep_removal_done() calls trace_xprtrdma_device_removal(NULL).
The tracepoint dereferences id->device->name and copies
id->route.addr.dst_addr, so the callback can crash the kernel with a
NULL pointer dereference.

Store the rdma_cm_id in ep->re_id immediately before publishing
ep->re_rn. The existing error path still destroys the id directly if
registration fails; ep is then freed by the caller without using
ep->re_id. Remove the later duplicate assignment in rpcrdma_ep_create().

Fixes: 3f4eb9ff9234 ("xprtrdma: Handle device removal outside of the CM event handler")
Assisted-by: kres:openai-gpt-5
Signed-off-by: Chris Mason <[email protected]>
Signed-off-by: Chuck Lever <[email protected]>
---
 net/sunrpc/xprtrdma/verbs.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/sunrpc/xprtrdma/verbs.c b/net/sunrpc/xprtrdma/verbs.c
index 354d5c0eb04f..ea78f82ec4d3 100644
--- a/net/sunrpc/xprtrdma/verbs.c
+++ b/net/sunrpc/xprtrdma/verbs.c
@@ -334,6 +334,7 @@ static struct rdma_cm_id *rpcrdma_create_id(struct rpcrdma_xprt *r_xprt,
 	if (rc)
 		goto out;
 
+	ep->re_id = id;
 	rc = rpcrdma_rn_register(id->device, &ep->re_rn, rpcrdma_ep_removal_done);
 	if (rc)
 		goto out;
@@ -406,7 +407,6 @@ static int rpcrdma_ep_create(struct rpcrdma_xprt *r_xprt)
 	}
 	__module_get(THIS_MODULE);
 	device = id->device;
-	ep->re_id = id;
 	reinit_completion(&ep->re_done);
 
 	ep->re_max_requests = r_xprt->rx_xprt.max_reqs;

-- 
2.54.0