[PATCH 5.15 116/917] mctp: handle the struct sockaddr_mctp padding fields

Greg Kroah-Hartman
2021-11-16T01:08:52Z

From: Eugene Syromiatnikov <esyr@redhat.com>

commit 1e4b50f06d970d8da3474d2a0354450416710bda upstream.

In order to have the padding fields actually usable in the future,
there have to be checks that user space doesn't supply non-zero garbage
there. It is also worth setting these padding fields to zero, unless
it is known that they have been already zeroed.

Cc: stable@vger.kernel.org # v5.15
Fixes: 5a20dd46b8b84593 ("mctp: Be explicit about struct sockaddr_mctp padding")
Signed-off-by: Eugene Syromiatnikov <esyr@redhat.com>
Acked-by: Jeremy Kerr <jk@codeconstruct.com.au>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
net/mctp/af_mctp.c | 13 +++++++++++++
1 file changed, 13 insertions(+)

--- a/net/mctp/af_mctp.c
+++ b/net/mctp/af_mctp.c
@@ -30,6 +30,12 @@ static int mctp_release(struct socket *s
return 0;
}

+/* Generic sockaddr checks, padding checks only so far */
+static bool mctp_sockaddr_is_ok(const struct sockaddr_mctp *addr)
+{
+ return !addr->__smctp_pad0 && !addr->__smctp_pad1;
+}
+
static int mctp_bind(struct socket *sock, struct sockaddr *addr, int addrlen)
{
struct sock *sk = sock->sk;
@@ -49,6 +55,9 @@ static int mctp_bind(struct socket *sock
/* it's a valid sockaddr for MCTP, cast and do protocol checks */
smctp = (struct sockaddr_mctp *)addr;

+ if (!mctp_sockaddr_is_ok(smctp))
+ return -EINVAL;
+
lock_sock(sk);

/* TODO: allow rebind */
@@ -83,6 +92,8 @@ static int mctp_sendmsg(struct socket *s
return -EINVAL;
if (addr->smctp_family != AF_MCTP)
return -EINVAL;
+ if (!mctp_sockaddr_is_ok(addr))
+ return -EINVAL;
if (addr->smctp_tag & ~(MCTP_TAG_MASK | MCTP_TAG_OWNER))
return -EINVAL;

@@ -172,11 +183,13 @@ static int mctp_recvmsg(struct socket *s

addr = msg->msg_name;
addr->smctp_family = AF_MCTP;
+ addr->__smctp_pad0 = 0;
addr->smctp_network = cb->net;
addr->smctp_addr.s_addr = hdr->src;
addr->smctp_type = type;
addr->smctp_tag = hdr->flags_seq_tag &
(MCTP_HDR_TAG_MASK | MCTP_HDR_FLAG_TO);
+ addr->__smctp_pad1 = 0;
msg->msg_namelen = sizeof(*addr);
}