From: Eric Dumazet edumazet@google.com
[ 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@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 Signed-off-by: Sasha Levin sashal@kernel.org --- 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 98a64e8d9bdaa..17d721a6add72 100644 --- a/net/ipv6/udp.c +++ b/net/ipv6/udp.c @@ -1391,9 +1391,11 @@ 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; } }