[SCTP]: Add RCU synchronization around sctp_localaddr_list

sctp_localaddr_list is modified dynamically via NETDEV_UP
and NETDEV_DOWN events, but there is not synchronization
between writer (even handler) and readers.  As a result,
the readers can access an entry that has been freed and
crash the sytem.

Signed-off-by: Vlad Yasevich <vladislav.yasevich@hp.com>
Acked-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Acked-by: Sridhar Samdurala <sri@us.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

2 files changed, 7 insertions, 0 deletions

diff --git a/include/net/sctp/sctp.h b/include/net/sctp/sctp.h
index d529045c1679..c9cc00c85782 100644
--- a/include/net/sctp/sctp.h
+++ b/include/net/sctp/sctp.h
@@ -123,6 +123,7 @@
  * sctp/protocol.c
  */
 extern struct sock *sctp_get_ctl_sock(void);
+extern void sctp_local_addr_free(struct rcu_head *head);
 extern int sctp_copy_local_addr_list(struct sctp_bind_addr *,
                                      sctp_scope_t, gfp_t gfp,
                                      int flags);
diff --git a/include/net/sctp/structs.h b/include/net/sctp/structs.h
index c0d5848c33dc..a89e36197afb 100644
--- a/include/net/sctp/structs.h
+++ b/include/net/sctp/structs.h
@@ -207,6 +207,9 @@ extern struct sctp_globals {
          * It is a list of sctp_sockaddr_entry.
          */
         struct list_head local_addr_list;
+
+        /* Lock that protects the local_addr_list writers */
+        spinlock_t addr_list_lock;
         
         /* Flag to indicate if addip is enabled. */
         int addip_enable;
@@ -242,6 +245,7 @@ extern struct sctp_globals {
 #define sctp_port_alloc_lock            (sctp_globals.port_alloc_lock)
 #define sctp_port_hashtable             (sctp_globals.port_hashtable)
 #define sctp_local_addr_list            (sctp_globals.local_addr_list)
+#define sctp_local_addr_lock            (sctp_globals.addr_list_lock)
 #define sctp_addip_enable               (sctp_globals.addip_enable)
 #define sctp_prsctp_enable              (sctp_globals.prsctp_enable)
 
@@ -737,8 +741,10 @@ const union sctp_addr *sctp_source(const struct sctp_chunk *chunk);
 /* This is a structure for holding either an IPv6 or an IPv4 address.  */
 struct sctp_sockaddr_entry {
         struct list_head list;
+        struct rcu_head rcu;
         union sctp_addr a;
         __u8 use_as_src;
+        __u8 valid;
 };
 
 typedef struct sctp_chunk *(sctp_packet_phandler_t)(struct sctp_association *);