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udp6: fix potential access to stale information

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lena wang reported an issue caused by udpv6_sendmsg()
mangling msg->msg_name and msg->msg_namelen, which
are later read from ____sys_sendmsg() :

	/*
	 * If this is sendmmsg() and sending to current destination address was
	 * successful, remember it.
	 */
	if (used_address && err >= 0) {
		used_address->name_len = msg_sys->msg_namelen;
		if (msg_sys->msg_name)
			memcpy(&used_address->name, msg_sys->msg_name,
			       used_address->name_len);
	}

udpv6_sendmsg() wants to pretend the remote address family
is AF_INET in order to call udp_sendmsg().

A fix would be to modify the address in-place, instead
of using a local variable, but this could have other side effects.

Instead, restore initial values before we return from udpv6_sendmsg().

Fixes: c71d8ebe7a ("net: Fix security_socket_sendmsg() bypass problem.")
Reported-by: lena wang <lena.wang@mediatek.com>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: Maciej Żenczykowski <maze@google.com>
Link: https://lore.kernel.org/r/20230412130308.1202254-1-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Eric Dumazet 2023-04-12 13:03:08 +00:00 committed by Jakub Kicinski
parent 306dc21361
commit 1c5950fc6f
1 changed files with 5 additions and 3 deletions
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8
net/ipv6/udp.c
View File

@ -1395,9 +1395,11 @@ int udpv6_sendmsg(struct sock *sk, struct msghdr *msg, size_t len)
msg->msg_name = &sin;
msg->msg_namelen = sizeof(sin);
do_udp_sendmsg:
if (ipv6_only_sock(sk))
return -ENETUNREACH;
return udp_sendmsg(sk, msg, len);
err = ipv6_only_sock(sk) ?
-ENETUNREACH : udp_sendmsg(sk, msg, len);
msg->msg_name = sin6;
msg->msg_namelen = addr_len;
return err;
}
}