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udp: must lock the socket in udp_disconnect()

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Baozeng Ding reported KASAN traces showing uses after free in
udp_lib_get_port() and other related UDP functions.

A CONFIG_DEBUG_PAGEALLOC=y kernel would eventually crash.

I could write a reproducer with two threads doing :

static int sock_fd;
static void *thr1(void *arg)
{
	for (;;) {
		connect(sock_fd, (const struct sockaddr *)arg,
			sizeof(struct sockaddr_in));
	}
}

static void *thr2(void *arg)
{
	struct sockaddr_in unspec;

	for (;;) {
		memset(&unspec, 0, sizeof(unspec));
	        connect(sock_fd, (const struct sockaddr *)&unspec,
			sizeof(unspec));
        }
}

Problem is that udp_disconnect() could run without holding socket lock,
and this was causing list corruptions.

Signed-off-by: Eric Dumazet <[email protected]>
Reported-by: Baozeng Ding <[email protected]>
Signed-off-by: David S. Miller <[email protected]>
This commit is contained in:
Eric Dumazet 2016-10-20 09:39:40 -07:00 • committed by David S. Miller
commit 286c72deab
8 changed files with 18 additions and 8 deletions
Download patch file Download diff file Expand all files Collapse all files

2
net/ipv4/ping.c
View file

@ -994,7 +994,7 @@ struct proto ping_prot = {
.init = ping_init_sock,
.close = ping_close,
.connect = ip4_datagram_connect,
.disconnect = udp_disconnect,
.disconnect = __udp_disconnect,
.setsockopt = ip_setsockopt,
.getsockopt = ip_getsockopt,
.sendmsg = ping_v4_sendmsg,

2
net/ipv4/raw.c
View file

@ -918,7 +918,7 @@ struct proto raw_prot = {
.close = raw_close,
.destroy = raw_destroy,
.connect = ip4_datagram_connect,
.disconnect = udp_disconnect,
.disconnect = __udp_disconnect,
.ioctl = raw_ioctl,
.init = raw_init,
.setsockopt = raw_setsockopt,

13
net/ipv4/udp.c
View file

@ -1345,7 +1345,7 @@ csum_copy_err:
goto try_again;
}
int udp_disconnect(struct sock *sk, int flags)
int __udp_disconnect(struct sock *sk, int flags)
{
struct inet_sock *inet = inet_sk(sk);
/*
@ -1367,6 +1367,15 @@ int udp_disconnect(struct sock *sk, int flags)
sk_dst_reset(sk);
return 0;
}
EXPORT_SYMBOL(__udp_disconnect);
int udp_disconnect(struct sock *sk, int flags)
{
lock_sock(sk);
__udp_disconnect(sk, flags);
release_sock(sk);
return 0;
}
EXPORT_SYMBOL(udp_disconnect);
void udp_lib_unhash(struct sock *sk)
@ -2193,7 +2202,7 @@ int udp_abort(struct sock *sk, int err)
sk->sk_err = err;
sk->sk_error_report(sk);
udp_disconnect(sk, 0);
__udp_disconnect(sk, 0);
release_sock(sk);