netlink: Always copy on mmap TX.

[cascardo/linux.git] / net / netlink / af_netlink.c

diff --git a/net/netlink/af_netlink.c b/net/netlink/af_netlink.c
index ef5f77b..a64680a 100644 (file)
--- a/net/netlink/af_netlink.c
+++ b/net/netlink/af_netlink.c
@@ -525,14 +525,14 @@ out:
        return err;
 }
 
-static void netlink_frame_flush_dcache(const struct nl_mmap_hdr *hdr)
+static void netlink_frame_flush_dcache(const struct nl_mmap_hdr *hdr, unsigned int nm_len)
 {
 #if ARCH_IMPLEMENTS_FLUSH_DCACHE_PAGE == 1
        struct page *p_start, *p_end;
 
        /* First page is flushed through netlink_{get,set}_status */
        p_start = pgvec_to_page(hdr + PAGE_SIZE);
-       p_end   = pgvec_to_page((void *)hdr + NL_MMAP_HDRLEN + hdr->nm_len - 1);
+       p_end   = pgvec_to_page((void *)hdr + NL_MMAP_HDRLEN + nm_len - 1);
        while (p_start <= p_end) {
                flush_dcache_page(p_start);
                p_start++;
@@ -714,24 +714,16 @@ static int netlink_mmap_sendmsg(struct sock *sk, struct msghdr *msg,
        struct nl_mmap_hdr *hdr;
        struct sk_buff *skb;
        unsigned int maxlen;
-       bool excl = true;
        int err = 0, len = 0;
 
-       /* Netlink messages are validated by the receiver before processing.
-        * In order to avoid userspace changing the contents of the message
-        * after validation, the socket and the ring may only be used by a
-        * single process, otherwise we fall back to copying.
-        */
-       if (atomic_long_read(&sk->sk_socket->file->f_count) > 1 ||
-           atomic_read(&nlk->mapped) > 1)
-               excl = false;
-
        mutex_lock(&nlk->pg_vec_lock);
 
        ring   = &nlk->tx_ring;
        maxlen = ring->frame_size - NL_MMAP_HDRLEN;
 
        do {
+               unsigned int nm_len;
+
                hdr = netlink_current_frame(ring, NL_MMAP_STATUS_VALID);
                if (hdr == NULL) {
                        if (!(msg->msg_flags & MSG_DONTWAIT) &&
@@ -739,35 +731,23 @@ static int netlink_mmap_sendmsg(struct sock *sk, struct msghdr *msg,
                                schedule();
                        continue;
                }
-               if (hdr->nm_len > maxlen) {
+
+               nm_len = ACCESS_ONCE(hdr->nm_len);
+               if (nm_len > maxlen) {
                        err = -EINVAL;
                        goto out;
                }
 
-               netlink_frame_flush_dcache(hdr);
+               netlink_frame_flush_dcache(hdr, nm_len);
 
-               if (likely(dst_portid == 0 && dst_group == 0 && excl)) {
-                       skb = alloc_skb_head(GFP_KERNEL);
-                       if (skb == NULL) {
-                               err = -ENOBUFS;
-                               goto out;
-                       }
-                       sock_hold(sk);
-                       netlink_ring_setup_skb(skb, sk, ring, hdr);
-                       NETLINK_CB(skb).flags |= NETLINK_SKB_TX;
-                       __skb_put(skb, hdr->nm_len);
-                       netlink_set_status(hdr, NL_MMAP_STATUS_RESERVED);
-                       atomic_inc(&ring->pending);
-               } else {
-                       skb = alloc_skb(hdr->nm_len, GFP_KERNEL);
-                       if (skb == NULL) {
-                               err = -ENOBUFS;
-                               goto out;
-                       }
-                       __skb_put(skb, hdr->nm_len);
-                       memcpy(skb->data, (void *)hdr + NL_MMAP_HDRLEN, hdr->nm_len);
-                       netlink_set_status(hdr, NL_MMAP_STATUS_UNUSED);
+               skb = alloc_skb(nm_len, GFP_KERNEL);
+               if (skb == NULL) {
+                       err = -ENOBUFS;
+                       goto out;
                }
+               __skb_put(skb, nm_len);
+               memcpy(skb->data, (void *)hdr + NL_MMAP_HDRLEN, nm_len);
+               netlink_set_status(hdr, NL_MMAP_STATUS_UNUSED);
 
                netlink_increment_head(ring);
 
@@ -813,7 +793,7 @@ static void netlink_queue_mmaped_skb(struct sock *sk, struct sk_buff *skb)
        hdr->nm_pid     = NETLINK_CB(skb).creds.pid;
        hdr->nm_uid     = from_kuid(sk_user_ns(sk), NETLINK_CB(skb).creds.uid);
        hdr->nm_gid     = from_kgid(sk_user_ns(sk), NETLINK_CB(skb).creds.gid);
-       netlink_frame_flush_dcache(hdr);
+       netlink_frame_flush_dcache(hdr, hdr->nm_len);
        netlink_set_status(hdr, NL_MMAP_STATUS_VALID);
 
        NETLINK_CB(skb).flags |= NETLINK_SKB_DELIVERED;