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>

1 files changed, 19 insertions, 3 deletions

diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index fdd88c3803a6..a4a0b6b3bcf2 100644
--- 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)