netlink: Always copy on mmap TX.
[ Upstream commit 4682a0358639b29cf69437ed909c6221f8c89847 ]
Checking the file f_count and the nlk->mapped count is not completely
sufficient to prevent the mmap'd area contents from changing from
under us during netlink mmap sendmsg() operations.
Be careful to sample the header's length field only once, because this
could change from under us as well.
Fixes: 5fd96123ee19 ("netlink: implement memory mapped sendmsg()")
Signed-off-by: David S. Miller <davem@davemloft.net>
Acked-by: Daniel Borkmann <dborkman@redhat.com>
Acked-by: Thomas Graf <tgraf@suug.ch>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
diff --git a/net/netlink/af_netlink.c b/net/netlink/af_netlink.c
index b6bf8e8..9222b15 100644
--- a/net/netlink/af_netlink.c
+++ b/net/netlink/af_netlink.c
@@ -526,14 +526,14 @@
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++;
@@ -715,24 +715,16 @@
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) &&
@@ -740,35 +732,23 @@
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);
@@ -814,7 +794,7 @@
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;