[PATCH v3] selinux: Fix error priority for bind with AF_UNSPEC on PF_INET6 socket

[Mickaël Salaün]

The IPv6 network stack first checks the sockaddr length (-EINVAL error)
before checking the family (-EAFNOSUPPORT error).

This was discovered thanks to commit a549d055a22e ("selftests/landlock:
Add network tests").

Cc: Eric Paris <eparis at parisplace.org>
Cc: Konstantin Meskhidze <konstantin.meskhidze at huawei.com>
Cc: Paul Moore <paul at paul-moore.com>
Cc: Stephen Smalley <stephen.smalley.work at gmail.com>
Reported-by: Muhammad Usama Anjum <usama.anjum at collabora.com>
Closes: https://lore.kernel.org/r/0584f91c-537c-4188-9e4f-04f192565667@collabora.com
Fixes: 0f8db8cc73df ("selinux: add AF_UNSPEC and INADDR_ANY checks to selinux_socket_bind()")
Signed-off-by: Mickaël Salaün <mic at digikod.net>
---

Changes since v2:
https://lore.kernel.org/r/20231229171922.106190-1-mic@digikod.net
* Add !PF_INET6 check and comments (suggested by Paul).
* s/AF_INET/PF_INET/g (cosmetic change).

Changes since v1:
https://lore.kernel.org/r/20231228113917.62089-1-mic@digikod.net
* Use the "family" variable (suggested by Paul).
---
 security/selinux/hooks.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
index feda711c6b7b..8b1429eb2db5 100644
--- a/security/selinux/hooks.c
+++ b/security/selinux/hooks.c
@@ -4667,6 +4667,13 @@ static int selinux_socket_bind(struct socket *sock, struct sockaddr *address, in
 				return -EINVAL;
 			addr4 = (struct sockaddr_in *)address;
 			if (family_sa == AF_UNSPEC) {
+				if (family == PF_INET6) {
+					/* Length check from inet6_bind_sk() */
+					if (addrlen < SIN6_LEN_RFC2133)
+						return -EINVAL;
+					/* Family check from __inet6_bind() */
+					goto err_af;
+				}
 				/* see __inet_bind(), we only want to allow
 				 * AF_UNSPEC if the address is INADDR_ANY
 				 */
-- 
2.43.0