sctp: Add RCU protection to assoc->transport_addr_list

peer.transport_addr_list is currently only protected by sk_sock
which is inpractical to acquire for procfs dumping purposes.

This patch adds RCU protection allowing for the procfs readers to
enter RCU read-side critical sections.

Modification of the list continues to be serialized via sk_lock.

V2: Use list_del_rcu() in sctp_association_free() to be safe
    Skip transports marked dead when dumping for procfs

Cc: Vlad Yasevich <vyasevich@gmail.com>
Cc: Neil Horman <nhorman@tuxdriver.com>
Signed-off-by: Thomas Graf <tgraf@suug.ch>
Acked-by: Vlad Yasevich <vyasevich@gmail.com>
Acked-by: Neil Horman <nhorman@tuxdriver.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 12 insertions, 2 deletions

diff --git a/net/sctp/proc.c b/net/sctp/proc.c
index 06b05ee17d8d..8c19e97262ca 100644
--- a/net/sctp/proc.c
+++ b/net/sctp/proc.c
@@ -162,15 +162,20 @@ static void sctp_seq_dump_remote_addrs(struct seq_file *seq, struct sctp_associa
         struct sctp_af *af;
 
         primary = &assoc->peer.primary_addr;
-        list_for_each_entry(transport, &assoc->peer.transport_addr_list,
+        rcu_read_lock();
+        list_for_each_entry_rcu(transport, &assoc->peer.transport_addr_list,
                         transports) {
                 addr = &transport->ipaddr;
+                if (transport->dead)
+                        continue;
+
                 af = sctp_get_af_specific(addr->sa.sa_family);
                 if (af->cmp_addr(addr, primary)) {
                         seq_printf(seq, "*");
                 }
                 af->seq_dump_addr(seq, addr);
         }
+        rcu_read_unlock();
 }
 
 static void * sctp_eps_seq_start(struct seq_file *seq, loff_t *pos)
@@ -441,12 +446,16 @@ static int sctp_remaddr_seq_show(struct seq_file *seq, void *v)
         head = &sctp_assoc_hashtable[hash];
         sctp_local_bh_disable();
         read_lock(&head->lock);
+        rcu_read_lock();
         sctp_for_each_hentry(epb, node, &head->chain) {
                 if (!net_eq(sock_net(epb->sk), seq_file_net(seq)))
                         continue;
                 assoc = sctp_assoc(epb);
-                list_for_each_entry(tsp, &assoc->peer.transport_addr_list,
+                list_for_each_entry_rcu(tsp, &assoc->peer.transport_addr_list,
                                         transports) {
+                        if (tsp->dead)
+                                continue;
+
                         /*
                          * The remote address (ADDR)
                          */
@@ -492,6 +501,7 @@ static int sctp_remaddr_seq_show(struct seq_file *seq, void *v)
                 }
         }
 
+        rcu_read_unlock();
         read_unlock(&head->lock);
         sctp_local_bh_enable();