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Subject[PATCH 4.2 24/61] tcp: fix potential huge kmalloc() calls in TCP_REPAIR
Date
4.2-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Eric Dumazet <edumazet@google.com>

[ Upstream commit 5d4c9bfbabdb1d497f21afd81501e5c54b0c85d9 ]

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
net/ipv4/tcp_input.c | 22 +++++++++++++++++++---
1 file changed, 19 insertions(+), 3 deletions(-)

--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -4434,19 +4434,34 @@ static int __must_check tcp_queue_rcv(st
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;
@@ -4462,7 +4477,8 @@ int tcp_send_rcvq(struct sock *sk, struc
err_free:
kfree_skb(skb);
err:
- return -ENOMEM;
+ return err;
+
}

static void tcp_data_queue(struct sock *sk, struct sk_buff *skb)



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