linux-kernel - [PATCH 4.7 143/143] SUNRPC: Fix infinite looping in rpc_clnt_iterate_for_each

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Message-Id: <20160905164436.655274523@linuxfoundation.org>
Date:   Mon,  5 Sep 2016 18:45:19 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Oleg Drokin <green@...uxhacker.ru>,
        Trond Myklebust <trond.myklebust@...marydata.com>,
        Jason L Tibbitts III <tibbs@...h.uh.edu>
Subject: [PATCH 4.7 143/143] SUNRPC: Fix infinite looping in rpc_clnt_iterate_for_each_xprt

4.7-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Trond Myklebust <trond.myklebust@...marydata.com>

commit bdc54d8e3cb4a41dddcabfd86d9eb3aa5f622b75 upstream.

If there were less than 2 entries in the multipath list, then
xprt_iter_next_entry_multiple() 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.

Reported-by: Oleg Drokin <green@...uxhacker.ru>
Fixes: 80b14d5e61ca ("SUNRPC: Add a structure to track multiple transports")
Signed-off-by: Trond Myklebust <trond.myklebust@...marydata.com>
Cc: Jason L Tibbitts III <tibbs@...h.uh.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 net/sunrpc/xprtmultipath.c |    8 +++-----
 1 file changed, 3 insertions(+), 5 deletions(-)

--- a/net/sunrpc/xprtmultipath.c
+++ b/net/sunrpc/xprtmultipath.c
@@ -271,14 +271,12 @@ struct rpc_xprt *xprt_iter_next_entry_mu
 		xprt_switch_find_xprt_t find_next)
 {
 	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 (xps->xps_nxprts < 2)
-		return xprt_switch_find_first_entry(head);
-	return xprt_switch_set_next_cursor(head, &xpi->xpi_cursor, find_next);
+	return xprt_switch_set_next_cursor(&xps->xps_xprt_list,
+			&xpi->xpi_cursor,
+			find_next);
 }
 
 static