netdev - [PATCH v2] include/uapi/linux/xfrm.h: Fix XFRM_MSG

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Message-ID: <20210912122234.GA22469@asgard.redhat.com>
Date:   Sun, 12 Sep 2021 14:22:34 +0200
From:   Eugene Syromiatnikov <esyr@...hat.com>
To:     Steffen Klassert <steffen.klassert@...unet.com>,
        Herbert Xu <herbert@...dor.apana.org.au>,
        "David S. Miller" <davem@...emloft.net>,
        Antony Antony <antony.antony@...unet.com>,
        Christian Langrock <christian.langrock@...unet.com>,
        Nicolas Dichtel <nicolas.dichtel@...nd.com>
Cc:     selinux@...r.kernel.org, Paul Moore <paul@...l-moore.com>,
        Stephen Smalley <stephen.smalley.work@...il.com>,
        Eric Paris <eparis@...isplace.org>, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, "Dmitry V. Levin" <ldv@...ace.io>,
        linux-api@...r.kernel.org
Subject: [PATCH v2] include/uapi/linux/xfrm.h: Fix XFRM_MSG_MAPPING ABI
 breakage

Commit 2d151d39073a ("xfrm: Add possibility to set the default to block
if we have no policy") broke ABI by changing the value of the XFRM_MSG_MAPPING
enum item, thus also evading the build-time check
in security/selinux/nlmsgtab.c:selinux_nlmsg_lookup for presence of proper
security permission checks in nlmsg_xfrm_perms.  Fix it by placing
XFRM_MSG_SETDEFAULT/XFRM_MSG_GETDEFAULT to the end of the enum, right before
__XFRM_MSG_MAX, and updating the nlmsg_xfrm_perms accordingly.

Fixes: 2d151d39073a ("xfrm: Add possibility to set the default to block if we have no policy")
References: https://lore.kernel.org/netdev/20210901151402.GA2557@altlinux.org/
Signed-off-by: Eugene Syromiatnikov <esyr@...hat.com>
---
v2:
 - Updated SELinux nlmsg_xfrm_perms permissions table and selinux_nlmsg_lookup
   build-time check accordingly.

v1: https://lore.kernel.org/lkml/20210901153407.GA20446@asgard.redhat.com/
---
 include/uapi/linux/xfrm.h   | 6 +++---
 security/selinux/nlmsgtab.c | 4 +++-
 2 files changed, 6 insertions(+), 4 deletions(-)

diff --git a/include/uapi/linux/xfrm.h b/include/uapi/linux/xfrm.h
index b96c1ea..26f456b1 100644
--- a/include/uapi/linux/xfrm.h
+++ b/include/uapi/linux/xfrm.h
@@ -213,13 +213,13 @@ enum {
 	XFRM_MSG_GETSPDINFO,
 #define XFRM_MSG_GETSPDINFO XFRM_MSG_GETSPDINFO
 
+	XFRM_MSG_MAPPING,
+#define XFRM_MSG_MAPPING XFRM_MSG_MAPPING
+
 	XFRM_MSG_SETDEFAULT,
 #define XFRM_MSG_SETDEFAULT XFRM_MSG_SETDEFAULT
 	XFRM_MSG_GETDEFAULT,
 #define XFRM_MSG_GETDEFAULT XFRM_MSG_GETDEFAULT
-
-	XFRM_MSG_MAPPING,
-#define XFRM_MSG_MAPPING XFRM_MSG_MAPPING
 	__XFRM_MSG_MAX
 };
 #define XFRM_MSG_MAX (__XFRM_MSG_MAX - 1)
diff --git a/security/selinux/nlmsgtab.c b/security/selinux/nlmsgtab.c
index d59276f..94ea2a8 100644
--- a/security/selinux/nlmsgtab.c
+++ b/security/selinux/nlmsgtab.c
@@ -126,6 +126,8 @@ static const struct nlmsg_perm nlmsg_xfrm_perms[] =
 	{ XFRM_MSG_NEWSPDINFO,	NETLINK_XFRM_SOCKET__NLMSG_WRITE },
 	{ XFRM_MSG_GETSPDINFO,	NETLINK_XFRM_SOCKET__NLMSG_READ  },
 	{ XFRM_MSG_MAPPING,	NETLINK_XFRM_SOCKET__NLMSG_READ  },
+	{ XFRM_MSG_SETDEFAULT,	NETLINK_XFRM_SOCKET__NLMSG_WRITE },
+	{ XFRM_MSG_GETDEFAULT,	NETLINK_XFRM_SOCKET__NLMSG_READ  },
 };
 
 static const struct nlmsg_perm nlmsg_audit_perms[] =
@@ -189,7 +191,7 @@ int selinux_nlmsg_lookup(u16 sclass, u16 nlmsg_type, u32 *perm)
 		 * structures at the top of this file with the new mappings
 		 * before updating the BUILD_BUG_ON() macro!
 		 */
-		BUILD_BUG_ON(XFRM_MSG_MAX != XFRM_MSG_MAPPING);
+		BUILD_BUG_ON(XFRM_MSG_MAX != XFRM_MSG_GETDEFAULT);
 		err = nlmsg_perm(nlmsg_type, perm, nlmsg_xfrm_perms,
 				 sizeof(nlmsg_xfrm_perms));
 		break;
-- 
2.1.4