[Devel] [PATCH] ms/tcp: fix potential huge kmalloc() calls in TCP_REPAIR

[Andrey Ryabinin]

On 4/9/19 1:19 PM, Andrey Ryabinin wrote:
> 
> 
> On 4/9/19 12:34 PM, Konstantin Khorenko wrote:
>> From: Eric Dumazet <edumazet at google.com>
>>
>> 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 at google.com>
>> Cc: Pavel Emelyanov <xemul at parallels.com>
>> Acked-by: Pavel Emelyanov <xemul at parallels.com>
>> Signed-off-by: David S. Miller <davem at davemloft.net>
>>
>> CRIU often triggers 8 order page allocation while restoring TCP sockets
>> without this patch.
>> https://jira.sw.ru/browse/PSBM-93672
>>
>> (cherry picked from commit 5d4c9bfbabdb1d497f21afd81501e5c54b0c85d9)
>> Signed-off-by: Konstantin Khorenko <khorenko at virtuozzo.com>
>> ---
>>  net/ipv4/tcp_input.c | 22 +++++++++++++++++++---
>>  1 file changed, 19 insertions(+), 3 deletions(-)
>>
>> diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
>> index 015c6fd7ec83..d0a6f767189d 100644
>> --- a/net/ipv4/tcp_input.c
>> +++ b/net/ipv4/tcp_input.c
>> @@ -4470,19 +4470,34 @@ 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);
> 
>              skb_copy_datagram_iovec(skb, 0, msg->msg_iov, size) ?
       
         Correction: skb_copy_datagram_from_iovec(skb, 0, msg->msg_iov, 0, size)
> 
> 
>> +	if (err)
>>  		goto err_free;
>>  
>>  	TCP_SKB_CB(skb)->seq = tcp_sk(sk)->rcv_nxt;
>> @@ -4498,7 +4513,8 @@ 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)
>>