linux-kernel - [PATCH 4.18 118/150] tipc: fix unsafe rcu locking when accessing publication list

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Date:   Fri,  2 Nov 2018 19:34:40 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Tung Nguyen <tung.q.nguyen@...tech.com.au>,
        Jon Maloy <jon.maloy@...csson.com>,
        "David S. Miller" <davem@...emloft.net>
Subject: [PATCH 4.18 118/150] tipc: fix unsafe rcu locking when accessing publication list

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

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

From: Tung Nguyen <tung.q.nguyen@...tech.com.au>

[ Upstream commit d3092b2efca1cd1d492d0b08499a2066c5ca8cec ]

The binding table's 'cluster_scope' list is rcu protected to handle
races between threads changing the list and those traversing the list at
the same moment. We have now found that the function named_distribute()
uses the regular list_for_each() macro to traverse the said list.
Likewise, the function tipc_named_withdraw() is removing items from the
same list using the regular list_del() call. When these two functions
execute in parallel we see occasional crashes.

This commit fixes this by adding the missing _rcu() suffixes.

Signed-off-by: Tung Nguyen <tung.q.nguyen@...tech.com.au>
Signed-off-by: Jon Maloy <jon.maloy@...csson.com>
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 net/tipc/name_distr.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- a/net/tipc/name_distr.c
+++ b/net/tipc/name_distr.c
@@ -115,7 +115,7 @@ struct sk_buff *tipc_named_withdraw(stru
 	struct sk_buff *buf;
 	struct distr_item *item;
 
-	list_del(&publ->binding_node);
+	list_del_rcu(&publ->binding_node);
 
 	if (publ->scope == TIPC_NODE_SCOPE)
 		return NULL;
@@ -147,7 +147,7 @@ static void named_distribute(struct net
 			ITEM_SIZE) * ITEM_SIZE;
 	u32 msg_rem = msg_dsz;
 
-	list_for_each_entry(publ, pls, binding_node) {
+	list_for_each_entry_rcu(publ, pls, binding_node) {
 		/* Prepare next buffer: */
 		if (!skb) {
 			skb = named_prepare_buf(net, PUBLICATION, msg_rem,