From: Eric Dumazet <edumazet@xxxxxxxxxx>
[ Upstream commit 1c5950fc6fe996235f1d18539b9c6b64b597f50f ]
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: c71d8ebe7a44 ("net: Fix security_socket_sendmsg() bypass problem.")
Reported-by: lena wang <lena.wang@xxxxxxxxxxxx>
Signed-off-by: Eric Dumazet <edumazet@xxxxxxxxxx>
Reviewed-by: Maciej Żenczykowski <maze@xxxxxxxxxx>
Link: https://lore.kernel.org/r/20230412130308.1202254-1-edumazet@xxxxxxxxxx
Signed-off-by: Jakub Kicinski <kuba@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
net/ipv6/udp.c | 8 +++++---
1 file changed, 5 insertions(+), 3 deletions(-)
diff --git a/net/ipv6/udp.c b/net/ipv6/udp.c
index 1805cc5f7418b..20cc08210c700 100644
--- a/net/ipv6/udp.c
+++ b/net/ipv6/udp.c
@@ -1340,9 +1340,11 @@ 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;
}
}
--
2.39.2
