netdev - [PATCH 2/2] SUNRPC: Fix infinite looping in rpc_clnt_iterate_for_each

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Date:   Sat,  4 Jun 2022 11:28:10 +0800
From:   Xiaohui Zhang <ruc_zhangxiaohui@....com>
To:     Xiaohui Zhang <ruc_zhangxiaohui@....com>,
        Trond Myklebust <trond.myklebust@...merspace.com>,
        Anna Schumaker <anna@...nel.org>,
        "David S . Miller" <davem@...emloft.net>,
        linux-nfs@...r.kernel.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Cc:     hifoolno <553441439@...com>
Subject: [PATCH 2/2] SUNRPC: Fix infinite looping in rpc_clnt_iterate_for_each_xprt

From: hifoolno <553441439@...com>

If there were less than 2 entries in the multipath list, then
xprt_iter_current_entry() would never advance beyond the
first entry, which is correct for round robin behaviour, but not
for the list iteration.

The end result would be infinite looping in rpc_clnt_iterate_for_each_xprt()
as we would never see the xprt == NULL condition fulfilled.

Signed-off-by: hifoolno <553441439@...com>
---
 net/sunrpc/xprtmultipath.c | 8 +++-----
 1 file changed, 3 insertions(+), 5 deletions(-)

diff --git a/net/sunrpc/xprtmultipath.c b/net/sunrpc/xprtmultipath.c
index 1693f81aae37..23c3aae1bb5b 100644
--- a/net/sunrpc/xprtmultipath.c
+++ b/net/sunrpc/xprtmultipath.c
@@ -278,14 +278,12 @@ static
 struct rpc_xprt *xprt_iter_current_entry(struct rpc_xprt_iter *xpi)
 {
 	struct rpc_xprt_switch *xps = rcu_dereference(xpi->xpi_xpswitch);
-	struct list_head *head;
 
 	if (xps == NULL)
 		return NULL;
-	head = &xps->xps_xprt_list;
-	if (xpi->xpi_cursor == NULL || xps->xps_nxprts < 2)
-		return xprt_switch_find_first_entry(head);
-	return xprt_switch_find_current_entry(head, xpi->xpi_cursor);
+	return xprt_switch_set_next_cursor(&xps->xps_xprt_list,
+		&xpi->xpi_cursor,
+		find_next);
 }
 
 bool rpc_xprt_switch_has_addr(struct rpc_xprt_switch *xps,
-- 
2.17.1