selinux: log anon inode class name

Log the anonymous inode class name in the security hook
inode_init_security_anon. This name is the key for name based type
transitions on the anon_inode security class on creation. Example:

type=AVC msg=audit(02/16/22 22:02:50.585:216) : avc: granted \
{ create } for pid=2136 comm=mariadbd anonclass=[io_uring] \
scontext=system_u:system_r:mysqld_t:s0 \
tcontext=system_u:system_r:mysqld_iouring_t:s0 tclass=anon_inode

Add a new LSM audit data type holding the inode and the class name.

Signed-off-by: Christian Göttsche <[e-mail]>
[PM: adjusted 'anonclass' to be a trusted string, cgzones approved]
Signed-off-by: Paul Moore <[e-mail]>

include/linux/lsm_audit.h

···
 #define LSM_AUDIT_DATA_IBENDPORT 14
 #define LSM_AUDIT_DATA_LOCKDOWN 15
 #define LSM_AUDIT_DATA_NOTIFICATION 16
+#define LSM_AUDIT_DATA_ANONINODE	17
 	union 	{
 		struct path path;
 		struct dentry *dentry;
···
 		struct lsm_ibpkey_audit *ibpkey;
 		struct lsm_ibendport_audit *ibendport;
 		int reason;
+		const char *anonclass;
 	} u;
 	/* this union contains LSM specific data */
 	union {

security/lsm_audit.c

···
 		audit_log_format(ab, " lockdown_reason=\"%s\"",
 				 lockdown_reasons[a->u.reason]);
 		break;
+	case LSM_AUDIT_DATA_ANONINODE:
+		audit_log_format(ab, " anonclass=%s", a->u.anonclass);
+		break;
 	} /* switch (a->type) */
 }
 

security/selinux/hooks.c

···
 	 * allowed to actually create this type of anonymous inode.
 	 */
 
-	ad.type = LSM_AUDIT_DATA_INODE;
-	ad.u.inode = inode;
+	ad.type = LSM_AUDIT_DATA_ANONINODE;
+	ad.u.anonclass = name ? (const char *)name->name : "?";
 
 	return avc_has_perm(&selinux_state,
 			    tsec->sid,