aboutsummaryrefslogtreecommitdiff
path: root/net/netlink
diff options
context:
space:
mode:
authorPatrick McHardy <kaber@trash.net>2013-04-17 06:47:03 +0000
committerDavid S. Miller <davem@davemloft.net>2013-04-19 14:57:57 -0400
commit5fd96123ee19b96be7d7b57fd42227e1a146ef05 (patch)
tree291383cb7d7b8b719bb370fe8483c8109a93aaff /net/netlink
parent9652e931e73be7e54a9c40e9bcd4bbdafe92a406 (diff)
downloadlinux-5fd96123ee19b96be7d7b57fd42227e1a146ef05.tar.gz
netlink: implement memory mapped sendmsg()
Add support for mmap'ed sendmsg() to netlink. Since the kernel validates received messages before processing them, the code makes sure userspace can't modify the message contents after invoking sendmsg(). To do that only a single mapping of the TX ring is allowed to exist and the socket must not be shared. If either of these two conditions does not hold, it falls back to copying. Signed-off-by: Patrick McHardy <kaber@trash.net> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/netlink')
-rw-r--r--net/netlink/af_netlink.c135
1 files changed, 129 insertions, 6 deletions
diff --git a/net/netlink/af_netlink.c b/net/netlink/af_netlink.c
index 6560635fd25..90504a0e42a 100644
--- a/net/netlink/af_netlink.c
+++ b/net/netlink/af_netlink.c
@@ -116,6 +116,11 @@ static bool netlink_skb_is_mmaped(const struct sk_buff *skb)
return NETLINK_CB(skb).flags & NETLINK_SKB_MMAPED;
}
+static bool netlink_tx_is_mmaped(struct sock *sk)
+{
+ return nlk_sk(sk)->tx_ring.pg_vec != NULL;
+}
+
static __pure struct page *pgvec_to_page(const void *addr)
{
if (is_vmalloc_addr(addr))
@@ -438,6 +443,9 @@ static unsigned int netlink_poll(struct file *file, struct socket *sock,
struct netlink_sock *nlk = nlk_sk(sk);
unsigned int mask;
+ if (nlk->cb != NULL && nlk->rx_ring.pg_vec != NULL)
+ netlink_dump(sk);
+
mask = datagram_poll(file, sock, wait);
spin_lock_bh(&sk->sk_receive_queue.lock);
@@ -483,10 +491,110 @@ static void netlink_ring_setup_skb(struct sk_buff *skb, struct sock *sk,
NETLINK_CB(skb).flags |= NETLINK_SKB_MMAPED;
NETLINK_CB(skb).sk = sk;
}
+
+static int netlink_mmap_sendmsg(struct sock *sk, struct msghdr *msg,
+ u32 dst_portid, u32 dst_group,
+ struct sock_iocb *siocb)
+{
+ struct netlink_sock *nlk = nlk_sk(sk);
+ struct netlink_ring *ring;
+ 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) > 2 ||
+ 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 {
+ hdr = netlink_current_frame(ring, NL_MMAP_STATUS_VALID);
+ if (hdr == NULL) {
+ if (!(msg->msg_flags & MSG_DONTWAIT) &&
+ atomic_read(&nlk->tx_ring.pending))
+ schedule();
+ continue;
+ }
+ if (hdr->nm_len > maxlen) {
+ err = -EINVAL;
+ goto out;
+ }
+
+ netlink_frame_flush_dcache(hdr);
+
+ 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);
+ }
+
+ netlink_increment_head(ring);
+
+ NETLINK_CB(skb).portid = nlk->portid;
+ NETLINK_CB(skb).dst_group = dst_group;
+ NETLINK_CB(skb).creds = siocb->scm->creds;
+
+ err = security_netlink_send(sk, skb);
+ if (err) {
+ kfree_skb(skb);
+ goto out;
+ }
+
+ if (unlikely(dst_group)) {
+ atomic_inc(&skb->users);
+ netlink_broadcast(sk, skb, dst_portid, dst_group,
+ GFP_KERNEL);
+ }
+ err = netlink_unicast(sk, skb, dst_portid,
+ msg->msg_flags & MSG_DONTWAIT);
+ if (err < 0)
+ goto out;
+ len += err;
+
+ } while (hdr != NULL ||
+ (!(msg->msg_flags & MSG_DONTWAIT) &&
+ atomic_read(&nlk->tx_ring.pending)));
+
+ if (len > 0)
+ err = len;
+out:
+ mutex_unlock(&nlk->pg_vec_lock);
+ return err;
+}
#else /* CONFIG_NETLINK_MMAP */
#define netlink_skb_is_mmaped(skb) false
+#define netlink_tx_is_mmaped(sk) false
#define netlink_mmap sock_no_mmap
#define netlink_poll datagram_poll
+#define netlink_mmap_sendmsg(sk, msg, dst_portid, dst_group, siocb) 0
#endif /* CONFIG_NETLINK_MMAP */
static void netlink_destroy_callback(struct netlink_callback *cb)
@@ -517,11 +625,16 @@ static void netlink_skb_destructor(struct sk_buff *skb)
hdr = netlink_mmap_hdr(skb);
sk = NETLINK_CB(skb).sk;
- if (!(NETLINK_CB(skb).flags & NETLINK_SKB_DELIVERED)) {
- hdr->nm_len = 0;
- netlink_set_status(hdr, NL_MMAP_STATUS_VALID);
+ if (NETLINK_CB(skb).flags & NETLINK_SKB_TX) {
+ netlink_set_status(hdr, NL_MMAP_STATUS_UNUSED);
+ ring = &nlk_sk(sk)->tx_ring;
+ } else {
+ if (!(NETLINK_CB(skb).flags & NETLINK_SKB_DELIVERED)) {
+ hdr->nm_len = 0;
+ netlink_set_status(hdr, NL_MMAP_STATUS_VALID);
+ }
+ ring = &nlk_sk(sk)->rx_ring;
}
- ring = &nlk_sk(sk)->rx_ring;
WARN_ON(atomic_read(&ring->pending) == 0);
atomic_dec(&ring->pending);
@@ -1230,8 +1343,9 @@ int netlink_attachskb(struct sock *sk, struct sk_buff *skb,
nlk = nlk_sk(sk);
- if (atomic_read(&sk->sk_rmem_alloc) > sk->sk_rcvbuf ||
- test_bit(NETLINK_CONGESTED, &nlk->state)) {
+ if ((atomic_read(&sk->sk_rmem_alloc) > sk->sk_rcvbuf ||
+ test_bit(NETLINK_CONGESTED, &nlk->state)) &&
+ !netlink_skb_is_mmaped(skb)) {
DECLARE_WAITQUEUE(wait, current);
if (!*timeo) {
if (!ssk || netlink_is_kernel(ssk))
@@ -1291,6 +1405,8 @@ static struct sk_buff *netlink_trim(struct sk_buff *skb, gfp_t allocation)
int delta;
WARN_ON(skb->sk != NULL);
+ if (netlink_skb_is_mmaped(skb))
+ return skb;
delta = skb->end - skb->tail;
if (delta * 2 < skb->truesize)
@@ -1815,6 +1931,13 @@ static int netlink_sendmsg(struct kiocb *kiocb, struct socket *sock,
goto out;
}
+ if (netlink_tx_is_mmaped(sk) &&
+ msg->msg_iov->iov_base == NULL) {
+ err = netlink_mmap_sendmsg(sk, msg, dst_portid, dst_group,
+ siocb);
+ goto out;
+ }
+
err = -EMSGSIZE;
if (len > sk->sk_sndbuf - 32)
goto out;