Patch "rds: tcp: atomically purge entries from rds_tcp_conn_list during netns delete" has been added to the 4.9-stable tree

[<gregkh@linuxfoundation.org>]

This is a note to let you know that I've just added the patch titled

    rds: tcp: atomically purge entries from rds_tcp_conn_list during netns delete

to the 4.9-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     rds-tcp-atomically-purge-entries-from-rds_tcp_conn_list-during-netns-delete.patch
and it can be found in the queue-4.9 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From f10b4cff98c6977668434fbf5dd58695eeca2897 Mon Sep 17 00:00:00 2001
From: Sowmini Varadhan <sowmini.varadhan@oracle.com>
Date: Thu, 30 Nov 2017 11:11:29 -0800
Subject: rds: tcp: atomically purge entries from rds_tcp_conn_list during netns delete

From: Sowmini Varadhan <sowmini.varadhan@oracle.com>

commit f10b4cff98c6977668434fbf5dd58695eeca2897 upstream.

The rds_tcp_kill_sock() function parses the rds_tcp_conn_list
to find the rds_connection entries marked for deletion as part
of the netns deletion under the protection of the rds_tcp_conn_lock.
Since the rds_tcp_conn_list tracks rds_tcp_connections (which
have a 1:1 mapping with rds_conn_path), multiple tc entries in
the rds_tcp_conn_list will map to a single rds_connection, and will
be deleted as part of the rds_conn_destroy() operation that is
done outside the rds_tcp_conn_lock.

The rds_tcp_conn_list traversal done under the protection of
rds_tcp_conn_lock should not leave any doomed tc entries in
the list after the rds_tcp_conn_lock is released, else another
concurrently executiong netns delete (for a differnt netns) thread
may trip on these entries.

Reported-by: syzbot <syzkaller@googlegroups.com>
Signed-off-by: Sowmini Varadhan <sowmini.varadhan@oracle.com>
Acked-by: Santosh Shilimkar <santosh.shilimkar@oracle.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 net/rds/tcp.c |    9 +++++++--
 net/rds/tcp.h |    1 +
 2 files changed, 8 insertions(+), 2 deletions(-)

--- a/net/rds/tcp.c
+++ b/net/rds/tcp.c
@@ -303,7 +303,8 @@ static void rds_tcp_conn_free(void *arg)
 	rdsdebug("freeing tc %p\n", tc);
 
 	spin_lock_irqsave(&rds_tcp_conn_lock, flags);
-	list_del(&tc->t_tcp_node);
+	if (!tc->t_tcp_node_detached)
+		list_del(&tc->t_tcp_node);
 	spin_unlock_irqrestore(&rds_tcp_conn_lock, flags);
 
 	kmem_cache_free(rds_tcp_conn_slab, tc);
@@ -528,8 +529,12 @@ static void rds_tcp_kill_sock(struct net
 
 		if (net != c_net || !tc->t_sock)
 			continue;
-		if (!list_has_conn(&tmp_list, tc->t_cpath->cp_conn))
+		if (!list_has_conn(&tmp_list, tc->t_cpath->cp_conn)) {
 			list_move_tail(&tc->t_tcp_node, &tmp_list);
+		} else {
+			list_del(&tc->t_tcp_node);
+			tc->t_tcp_node_detached = true;
+		}
 	}
 	spin_unlock_irq(&rds_tcp_conn_lock);
 	list_for_each_entry_safe(tc, _tc, &tmp_list, t_tcp_node) {
--- a/net/rds/tcp.h
+++ b/net/rds/tcp.h
@@ -11,6 +11,7 @@ struct rds_tcp_incoming {
 struct rds_tcp_connection {
 
 	struct list_head	t_tcp_node;
+	bool			t_tcp_node_detached;
 	struct rds_conn_path	*t_cpath;
 	/* t_conn_path_lock synchronizes the connection establishment between
 	 * rds_tcp_accept_one and rds_tcp_conn_path_connect


Patches currently in stable-queue which might be from sowmini.varadhan@oracle.com are

queue-4.9/rds-tcp-atomically-purge-entries-from-rds_tcp_conn_list-during-netns-delete.patch