tcp: fix potential huge kmalloc() calls in TCP_REPAIR

tcp_send_rcvq() is used for re-injecting data into tcp receive queue.

Problems :

- No check against size is performed, allowed user to fool kernel in
  attempting very large memory allocations, eventually triggering
  OOM when memory is fragmented.

- In case of fault during the copy we do not return correct errno.

Lets use alloc_skb_with_frags() to cook optimal skbs.

Fixes: 292e8d8c8538 ("tcp: Move rcvq sending to tcp_input.c")
Fixes: c0e88ff0f256 ("tcp: Repair socket queues")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Pavel Emelyanov <xemul@parallels.com>
Acked-by: Pavel Emelyanov <xemul@parallels.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index fdd88c3..a4a0b6b 100644 (file)
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -4481,19 +4481,34 @@ static int __must_check tcp_queue_rcv(struct sock *sk, struct sk_buff *skb, int
 int tcp_send_rcvq(struct sock *sk, struct msghdr *msg, size_t size)
 {
        struct sk_buff *skb;
+       int err = -ENOMEM;
+       int data_len = 0;
        bool fragstolen;
 
        if (size == 0)
                return 0;
 
-       skb = alloc_skb(size, sk->sk_allocation);
+       if (size > PAGE_SIZE) {
+               int npages = min_t(size_t, size >> PAGE_SHIFT, MAX_SKB_FRAGS);
+
+               data_len = npages << PAGE_SHIFT;
+               size = data_len + (size & ~PAGE_MASK);
+       }
+       skb = alloc_skb_with_frags(size - data_len, data_len,
+                                  PAGE_ALLOC_COSTLY_ORDER,
+                                  &err, sk->sk_allocation);
        if (!skb)
                goto err;
 
+       skb_put(skb, size - data_len);
+       skb->data_len = data_len;
+       skb->len = size;
+
        if (tcp_try_rmem_schedule(sk, skb, skb->truesize))
                goto err_free;
 
-       if (memcpy_from_msg(skb_put(skb, size), msg, size))
+       err = skb_copy_datagram_from_iter(skb, 0, &msg->msg_iter, size);
+       if (err)
                goto err_free;
 
        TCP_SKB_CB(skb)->seq = tcp_sk(sk)->rcv_nxt;
@@ -4509,7 +4524,8 @@ int tcp_send_rcvq(struct sock *sk, struct msghdr *msg, size_t size)
 err_free:
        kfree_skb(skb);
 err:
-       return -ENOMEM;
+       return err;
+
 }
 
 static void tcp_data_queue(struct sock *sk, struct sk_buff *skb)