[RFC PATCH v1 02/11] security: Add LSM_AUDIT_DATA_NS for namespace audit records

["Mickaël Salaün" <mic@digikod.net>]

Add a new LSM audit data type LSM_AUDIT_DATA_NS that logs namespace
information in audit records.  Two fields are provided, matching the
field names of struct ns_common:

- ns_type: the CLONE_NEW* flag identifying the namespace type, logged in
  hexadecimal.

- inum: the proc inode number identifying a specific namespace instance.
  Namespace inode numbers are allocated by proc_alloc_inum() via
  ida_alloc_max() bounded to UINT_MAX, so the value always fits in 32
  bits.

A new audit data type is needed because no existing LSM_AUDIT_DATA_*
type carries namespace information.  The closest alternatives (e.g.
LSM_AUDIT_DATA_TASK or LSM_AUDIT_DATA_NONE with custom strings) would
either lose the namespace type or require ad-hoc formatting that
bypasses the structured audit data union.

Cc: Christian Brauner <brauner@kernel.org>
Cc: Günther Noack <gnoack@google.com>
Cc: Paul Moore <paul@paul-moore.com>
Signed-off-by: Mickaël Salaün <mic@digikod.net>
---
 include/linux/lsm_audit.h | 5 +++++
 security/lsm_audit.c      | 4 ++++
 2 files changed, 9 insertions(+)

diff --git a/include/linux/lsm_audit.h b/include/linux/lsm_audit.h
index 382c56a97bba..6e20a56b8c22 100644
--- a/include/linux/lsm_audit.h
+++ b/include/linux/lsm_audit.h
@@ -78,6 +78,7 @@ struct common_audit_data {
 #define LSM_AUDIT_DATA_NOTIFICATION 16
 #define LSM_AUDIT_DATA_ANONINODE	17
 #define LSM_AUDIT_DATA_NLMSGTYPE	18
+#define LSM_AUDIT_DATA_NS		19
 	union 	{
 		struct path path;
 		struct dentry *dentry;
@@ -100,6 +101,10 @@ struct common_audit_data {
 		int reason;
 		const char *anonclass;
 		u16 nlmsg_type;
+		struct {
+			u32 ns_type;
+			unsigned int inum;
+		} ns;
 	} u;
 	/* this union contains LSM specific data */
 	union {
diff --git a/security/lsm_audit.c b/security/lsm_audit.c
index 7d623b00495c..7f71a77c1c12 100644
--- a/security/lsm_audit.c
+++ b/security/lsm_audit.c
@@ -403,6 +403,10 @@ void audit_log_lsm_data(struct audit_buffer *ab,
 	case LSM_AUDIT_DATA_NLMSGTYPE:
 		audit_log_format(ab, " nl-msgtype=%hu", a->u.nlmsg_type);
 		break;
+	case LSM_AUDIT_DATA_NS:
+		audit_log_format(ab, " namespace_type=0x%x namespace_inum=%u",
+				 a->u.ns.ns_type, a->u.ns.inum);
+		break;
 	} /* switch (a->type) */
 }
 
-- 
2.53.0