[NET]: Fix sk->sk_filter field access

Function sk_filter() is called from tcp_v{4,6}_rcv() functions with arg
needlock = 0, while socket is not locked at that moment. In order to avoid
this and similar issues in the future, use rcu for sk->sk_filter field read
protection.

Signed-off-by: Dmitry Mishin <dim@openvz.org>
Signed-off-by: Alexey Kuznetsov <kuznet@ms2.inr.ac.ru>
Signed-off-by: Kirill Korotaev <dev@openvz.org>

1 files changed, 7 insertions, 6 deletions

diff --git a/include/linux/filter.h b/include/linux/filter.h
index c6cb8f095088..91b2e3b9251e 100644
--- a/include/linux/filter.h
+++ b/include/linux/filter.h
@@ -25,10 +25,10 @@
  
 struct sock_filter      /* Filter block */
 {
-        __u16   code;   /* Actual filter code */
-        __u8    jt;     /* Jump true */
-        __u8    jf;     /* Jump false */
-        __u32   k;      /* Generic multiuse field */
+        __u16   code;   /* Actual filter code */
+        __u8    jt;     /* Jump true */
+        __u8    jf;     /* Jump false */
+        __u32   k;      /* Generic multiuse field */
 };
 
 struct sock_fprog       /* Required for SO_ATTACH_FILTER. */
@@ -41,8 +41,9 @@ struct sock_fprog	/* Required for SO_ATTACH_FILTER. */
 struct sk_filter
 {
         atomic_t                refcnt;
-        unsigned int            len;    /* Number of filter blocks */
-        struct sock_filter      insns[0];
+        unsigned int            len;    /* Number of filter blocks */
+        struct rcu_head         rcu;
+        struct sock_filter      insns[0];
 };
 
 static inline unsigned int sk_filter_len(struct sk_filter *fp)