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Subject[PATCH 4.7 143/143] SUNRPC: Fix infinite looping in rpc_clnt_iterate_for_each_xprt
Date
4.7-stable review patch.  If anyone has any objections, please let me know.

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

From: Trond Myklebust <trond.myklebust@primarydata.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@linuxhacker.ru>
Fixes: 80b14d5e61ca ("SUNRPC: Add a structure to track multiple transports")
Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
Cc: Jason L Tibbitts III <tibbs@math.uh.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.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

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