[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>

diff --git a/include/linux/filter.h b/include/linux/filter.h
index c6cb8f0..91b2e3b 100644 (file)
--- 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)

diff --git a/include/net/sock.h b/include/net/sock.h
index 337ebec..edd4d73 100644 (file)
--- a/include/net/sock.h
+++ b/include/net/sock.h
@@ -862,30 +862,24 @@ extern void sock_init_data(struct socket *sock, struct sock *sk);
  *
  */
 
-static inline int sk_filter(struct sock *sk, struct sk_buff *skb, int needlock)
+static inline int sk_filter(struct sock *sk, struct sk_buff *skb)
 {
        int err;
+       struct sk_filter *filter;
        
        err = security_sock_rcv_skb(sk, skb);
        if (err)
                return err;
        
-       if (sk->sk_filter) {
-               struct sk_filter *filter;
-               
-               if (needlock)
-                       bh_lock_sock(sk);
-               
-               filter = sk->sk_filter;
-               if (filter) {
-                       unsigned int pkt_len = sk_run_filter(skb, filter->insns,
-                                                            filter->len);
-                       err = pkt_len ? pskb_trim(skb, pkt_len) : -EPERM;
-               }
-
-               if (needlock)
-                       bh_unlock_sock(sk);
+       rcu_read_lock_bh();
+       filter = sk->sk_filter;
+       if (filter) {
+               unsigned int pkt_len = sk_run_filter(skb, filter->insns,
+                               filter->len);
+               err = pkt_len ? pskb_trim(skb, pkt_len) : -EPERM;
        }
+       rcu_read_unlock_bh();
+
        return err;
 }
 
@@ -897,6 +891,12 @@ static inline int sk_filter(struct sock *sk, struct sk_buff *skb, int needlock)
  *     Remove a filter from a socket and release its resources.
  */
  
+static inline void sk_filter_rcu_free(struct rcu_head *rcu)
+{
+       struct sk_filter *fp = container_of(rcu, struct sk_filter, rcu);
+       kfree(fp);
+}
+
 static inline void sk_filter_release(struct sock *sk, struct sk_filter *fp)
 {
        unsigned int size = sk_filter_len(fp);
@@ -904,7 +904,7 @@ static inline void sk_filter_release(struct sock *sk, struct sk_filter *fp)
        atomic_sub(size, &sk->sk_omem_alloc);
 
        if (atomic_dec_and_test(&fp->refcnt))
-               kfree(fp);
+               call_rcu_bh(&fp->rcu, sk_filter_rcu_free);
 }
 
 static inline void sk_filter_charge(struct sock *sk, struct sk_filter *fp)

diff --git a/net/core/filter.c b/net/core/filter.c
index 5b4486a..6732782 100644 (file)
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -422,10 +422,10 @@ int sk_attach_filter(struct sock_fprog *fprog, struct sock *sk)
        if (!err) {
                struct sk_filter *old_fp;
 
-               spin_lock_bh(&sk->sk_lock.slock);
-               old_fp = sk->sk_filter;
-               sk->sk_filter = fp;
-               spin_unlock_bh(&sk->sk_lock.slock);
+               rcu_read_lock_bh();
+               old_fp = rcu_dereference(sk->sk_filter);
+               rcu_assign_pointer(sk->sk_filter, fp);
+               rcu_read_unlock_bh();
                fp = old_fp;
        }
 

diff --git a/net/core/sock.c b/net/core/sock.c
index cfaf090..b77e155 100644 (file)
--- a/net/core/sock.c
+++ b/net/core/sock.c
@@ -247,11 +247,7 @@ int sock_queue_rcv_skb(struct sock *sk, struct sk_buff *skb)
                goto out;
        }
 
-       /* It would be deadlock, if sock_queue_rcv_skb is used
-          with socket lock! We assume that users of this
-          function are lock free.
-       */
-       err = sk_filter(sk, skb, 1);
+       err = sk_filter(sk, skb);
        if (err)
                goto out;
 
@@ -278,7 +274,7 @@ int sk_receive_skb(struct sock *sk, struct sk_buff *skb)
 {
        int rc = NET_RX_SUCCESS;
 
-       if (sk_filter(sk, skb, 0))
+       if (sk_filter(sk, skb))
                goto discard_and_relse;
 
        skb->dev = NULL;
@@ -606,15 +602,15 @@ set_rcvbuf:
                        break;
 
                case SO_DETACH_FILTER:
-                       spin_lock_bh(&sk->sk_lock.slock);
-                       filter = sk->sk_filter;
+                       rcu_read_lock_bh();
+                       filter = rcu_dereference(sk->sk_filter);
                         if (filter) {
-                               sk->sk_filter = NULL;
-                               spin_unlock_bh(&sk->sk_lock.slock);
+                               rcu_assign_pointer(sk->sk_filter, NULL);
                                sk_filter_release(sk, filter);
+                               rcu_read_unlock_bh();
                                break;
                        }
-                       spin_unlock_bh(&sk->sk_lock.slock);
+                       rcu_read_unlock_bh();
                        ret = -ENONET;
                        break;
 
@@ -884,10 +880,10 @@ void sk_free(struct sock *sk)
        if (sk->sk_destruct)
                sk->sk_destruct(sk);
 
-       filter = sk->sk_filter;
+       filter = rcu_dereference(sk->sk_filter);
        if (filter) {
                sk_filter_release(sk, filter);
-               sk->sk_filter = NULL;
+               rcu_assign_pointer(sk->sk_filter, NULL);
        }
 
        sock_disable_timestamp(sk);

diff --git a/net/dccp/ipv6.c b/net/dccp/ipv6.c
index f9c5e12..7a47399 100644 (file)
--- a/net/dccp/ipv6.c
+++ b/net/dccp/ipv6.c
@@ -970,7 +970,7 @@ static int dccp_v6_do_rcv(struct sock *sk, struct sk_buff *skb)
        if (skb->protocol == htons(ETH_P_IP))
                return dccp_v4_do_rcv(sk, skb);
 
-       if (sk_filter(sk, skb, 0))
+       if (sk_filter(sk, skb))
                goto discard;
 
        /*

diff --git a/net/decnet/dn_nsp_in.c b/net/decnet/dn_nsp_in.c
index 86f7f3b..72ecc6e 100644 (file)
--- a/net/decnet/dn_nsp_in.c
+++ b/net/decnet/dn_nsp_in.c
@@ -586,7 +586,7 @@ static __inline__ int dn_queue_skb(struct sock *sk, struct sk_buff *skb, int sig
                goto out;
         }
 
-       err = sk_filter(sk, skb, 0);
+       err = sk_filter(sk, skb);
        if (err)
                goto out;
 

diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
index 23b46e3..39b1798 100644 (file)
--- a/net/ipv4/tcp_ipv4.c
+++ b/net/ipv4/tcp_ipv4.c
@@ -1104,7 +1104,7 @@ process:
                goto discard_and_relse;
        nf_reset(skb);
 
-       if (sk_filter(sk, skb, 0))
+       if (sk_filter(sk, skb))
                goto discard_and_relse;
 
        skb->dev = NULL;

diff --git a/net/ipv6/tcp_ipv6.c b/net/ipv6/tcp_ipv6.c
index 2b18918..2546fc9 100644 (file)
--- a/net/ipv6/tcp_ipv6.c
+++ b/net/ipv6/tcp_ipv6.c
@@ -1075,7 +1075,7 @@ static int tcp_v6_do_rcv(struct sock *sk, struct sk_buff *skb)
        if (skb->protocol == htons(ETH_P_IP))
                return tcp_v4_do_rcv(sk, skb);
 
-       if (sk_filter(sk, skb, 0))
+       if (sk_filter(sk, skb))
                goto discard;
 
        /*
@@ -1232,7 +1232,7 @@ process:
        if (!xfrm6_policy_check(sk, XFRM_POLICY_IN, skb))
                goto discard_and_relse;
 
-       if (sk_filter(sk, skb, 0))
+       if (sk_filter(sk, skb))
                goto discard_and_relse;
 
        skb->dev = NULL;

diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c
index 300215b..f4ccb90 100644 (file)
--- a/net/packet/af_packet.c
+++ b/net/packet/af_packet.c
@@ -427,21 +427,24 @@ out_unlock:
 }
 #endif
 
-static inline unsigned run_filter(struct sk_buff *skb, struct sock *sk, unsigned res)
+static inline int run_filter(struct sk_buff *skb, struct sock *sk,
+                                                       unsigned *snaplen)
 {
        struct sk_filter *filter;
+       int err = 0;
 
-       bh_lock_sock(sk);
-       filter = sk->sk_filter;
-       /*
-        * Our caller already checked that filter != NULL but we need to
-        * verify that under bh_lock_sock() to be safe
-        */
-       if (likely(filter != NULL))
-               res = sk_run_filter(skb, filter->insns, filter->len);
-       bh_unlock_sock(sk);
+       rcu_read_lock_bh();
+       filter = rcu_dereference(sk->sk_filter);
+       if (filter != NULL) {
+               err = sk_run_filter(skb, filter->insns, filter->len);
+               if (!err)
+                       err = -EPERM;
+               else if (*snaplen > err)
+                       *snaplen = err;
+       }
+       rcu_read_unlock_bh();
 
-       return res;
+       return err;
 }
 
 /*
@@ -491,13 +494,8 @@ static int packet_rcv(struct sk_buff *skb, struct net_device *dev, struct packet
 
        snaplen = skb->len;
 
-       if (sk->sk_filter) {
-               unsigned res = run_filter(skb, sk, snaplen);
-               if (res == 0)
-                       goto drop_n_restore;
-               if (snaplen > res)
-                       snaplen = res;
-       }
+       if (run_filter(skb, sk, &snaplen) < 0)
+               goto drop_n_restore;
 
        if (atomic_read(&sk->sk_rmem_alloc) + skb->truesize >=
            (unsigned)sk->sk_rcvbuf)
@@ -593,13 +591,8 @@ static int tpacket_rcv(struct sk_buff *skb, struct net_device *dev, struct packe
 
        snaplen = skb->len;
 
-       if (sk->sk_filter) {
-               unsigned res = run_filter(skb, sk, snaplen);
-               if (res == 0)
-                       goto drop_n_restore;
-               if (snaplen > res)
-                       snaplen = res;
-       }
+       if (run_filter(skb, sk, &snaplen) < 0)
+               goto drop_n_restore;
 
        if (sk->sk_type == SOCK_DGRAM) {
                macoff = netoff = TPACKET_ALIGN(TPACKET_HDRLEN) + 16;

diff --git a/net/sctp/input.c b/net/sctp/input.c
index 8a34d95..03f65de 100644 (file)
--- a/net/sctp/input.c
+++ b/net/sctp/input.c
@@ -228,7 +228,7 @@ int sctp_rcv(struct sk_buff *skb)
                goto discard_release;
        nf_reset(skb);
 
-       if (sk_filter(sk, skb, 1))
+       if (sk_filter(sk, skb))
                 goto discard_release;
 
        /* Create an SCTP packet structure. */