[PATCH 3/3] RDMA/rtrs-srv: Reject an empty pathname

[Yuqiang Sun <izaiahsun@gmail.com>]

process_info_req() uses the pathname sent by the client as the name of
the session device and rejects names containing '/' or '.', but it
accepts an empty one.  dev_set_name() succeeds for it, and device_add()
then fails in kobject_add_internal(), which warns about the empty name.

Reject an empty pathname together with the other invalid ones.

Build-tested with x86_64 and arm64 allmodconfig (W=1, sparse): no new
warnings.  Run-tested under KVM with KASAN, lockdep and kmemleak, using
a small user-space rtrs client that sends an empty pathname: the server
now rejects it at the check above, nothing is reported, and an ordinary
rnbd map, I/O and unmap afterwards still work.  Not tested on RDMA
hardware.

Fixes: dea7bb3ad3e0 ("RDMA/rtrs: Do not allow sessname to contain special symbols / and .")
Cc: stable@vger.kernel.org
Assisted-by: Claude:claude-opus-5-5 kbound
Signed-off-by: Yuqiang Sun <izaiahsun@gmail.com>
---
 drivers/infiniband/ulp/rtrs/rtrs-srv.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/infiniband/ulp/rtrs/rtrs-srv.c b/drivers/infiniband/ulp/rtrs/rtrs-srv.c
index 56f0ab5a7619..d34a177f7ba2 100644
--- a/drivers/infiniband/ulp/rtrs/rtrs-srv.c
+++ b/drivers/infiniband/ulp/rtrs/rtrs-srv.c
@@ -823,6 +823,10 @@ static int process_info_req(struct rtrs_srv_con *con,
 		return err;
 	}
 
+	if (!msg->pathname[0]) {
+		rtrs_err(s, "pathname cannot be empty\n");
+		return -EINVAL;
+	}
 	if (strchr(msg->pathname, '/') || strchr(msg->pathname, '.')) {
 		rtrs_err(s, "pathname cannot contain / and .\n");
 		return -EINVAL;
-- 
2.53.0