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udp: fix integer overflow while computing available space in sk_rcvbuf 

When the size of the receive buffer for a socket is close to 2^31 when
computing if we have enough space in the buffer to copy a packet from
the queue to the buffer we might hit an integer overflow.

When an user set net.core.rmem_default to a value close to 2^31 UDP
packets are dropped because of this overflow. This can be visible, for
instance, with failure to resolve hostnames.

This can be fixed by casting sk_rcvbuf (which is an int) to unsigned
int, similarly to how it is done in TCP.

Signed-off-by: Antonio Messina <amessina@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
alistair/sunxi64-5.5-dsi
Antonio Messina 2019-12-19 15:08:03 +01:00 committed by David S. Miller
parent c601747175
commit feed8a4fc9
1 changed files with 1 additions and 1 deletions
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2
net/ipv4/udp.c
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@ -1475,7 +1475,7 @@ int __udp_enqueue_schedule_skb(struct sock *sk, struct sk_buff *skb)
* queue contains some other skb
*/
rmem = atomic_add_return(size, &sk->sk_rmem_alloc);
if (rmem > (size + sk->sk_rcvbuf))
if (rmem > (size + (unsigned int)sk->sk_rcvbuf))
goto uncharge_drop;
spin_lock(&list->lock);