lsm: infrastructure management of the dev_tun blob

Move management of the dev_tun security blob out of the individual
security modules and into the LSM infrastructure.  The security modules
tell the infrastructure how much space they require at initialization.
There are no longer any modules that require the dev_tun_free hook.
The hook definition has been removed.

Signed-off-by: Casey Schaufler <casey@schaufler-ca.com>
Reviewed-by: John Johansen <john.johansen@canonical.com>
[PM: subject tweak, selinux style fixes]
Signed-off-by: Paul Moore <paul@paul-moore.com>

include/linux/lsm_hook_defs.h

@@ -353,8 +353,7 @@ LSM_HOOK(void, LSM_RET_VOID, secmark_refcount_inc, void)
 LSM_HOOK(void, LSM_RET_VOID, secmark_refcount_dec, void)
 LSM_HOOK(void, LSM_RET_VOID, req_classify_flow, const struct request_sock *req,
 	 struct flowi_common *flic)
-LSM_HOOK(int, 0, tun_dev_alloc_security, void **security)
-LSM_HOOK(void, LSM_RET_VOID, tun_dev_free_security, void *security)
+LSM_HOOK(int, 0, tun_dev_alloc_security, void *security)
 LSM_HOOK(int, 0, tun_dev_create, void)
 LSM_HOOK(int, 0, tun_dev_attach_queue, void *security)
 LSM_HOOK(int, 0, tun_dev_attach, struct sock *sk, void *security)

include/linux/lsm_hooks.h

@@ -80,6 +80,7 @@ struct lsm_blob_sizes {
 	int	lbs_msg_msg;
 	int	lbs_task;
 	int	lbs_xattr_count; /* number of xattr slots in new_xattrs array */
+	int	lbs_tun_dev;
 };
 
 /**

security/security.c

@@ -232,6 +232,7 @@ static void __init lsm_set_blob_sizes(struct lsm_blob_sizes *needed)
 	lsm_set_blob_size(&needed->lbs_sock, &blob_sizes.lbs_sock);
 	lsm_set_blob_size(&needed->lbs_superblock, &blob_sizes.lbs_superblock);
 	lsm_set_blob_size(&needed->lbs_task, &blob_sizes.lbs_task);
+	lsm_set_blob_size(&needed->lbs_tun_dev, &blob_sizes.lbs_tun_dev);
 	lsm_set_blob_size(&needed->lbs_xattr_count,
 			  &blob_sizes.lbs_xattr_count);
 }
@@ -410,6 +411,7 @@ static void __init ordered_lsm_init(void)
 	init_debug("sock blob size       = %d\n", blob_sizes.lbs_sock);
 	init_debug("superblock blob size = %d\n", blob_sizes.lbs_superblock);
 	init_debug("task blob size       = %d\n", blob_sizes.lbs_task);
+	init_debug("tun device blob size = %d\n", blob_sizes.lbs_tun_dev);
 	init_debug("xattr slots          = %d\n", blob_sizes.lbs_xattr_count);
 
 	/*
@@ -4875,7 +4877,18 @@ EXPORT_SYMBOL(security_secmark_refcount_dec);
  */
 int security_tun_dev_alloc_security(void **security)
 {
-	return call_int_hook(tun_dev_alloc_security, security);
+	int rc;
+
+	rc = lsm_blob_alloc(security, blob_sizes.lbs_tun_dev, GFP_KERNEL);
+	if (rc)
+		return rc;
+
+	rc = call_int_hook(tun_dev_alloc_security, *security);
+	if (rc) {
+		kfree(*security);
+		*security = NULL;
+	}
+	return rc;
 }
 EXPORT_SYMBOL(security_tun_dev_alloc_security);
 
@@ -4887,7 +4900,7 @@ EXPORT_SYMBOL(security_tun_dev_alloc_security);
  */
 void security_tun_dev_free_security(void *security)
 {
-	call_void_hook(tun_dev_free_security, security);
+	kfree(security);
 }
 EXPORT_SYMBOL(security_tun_dev_free_security);
 

security/selinux/hooks.c

@@ -5578,24 +5578,14 @@ static void selinux_req_classify_flow(const struct request_sock *req,
 	flic->flowic_secid = req->secid;
 }
 
-static int selinux_tun_dev_alloc_security(void **security)
+static int selinux_tun_dev_alloc_security(void *security)
 {
-	struct tun_security_struct *tunsec;
+	struct tun_security_struct *tunsec = selinux_tun_dev(security);
 
-	tunsec = kzalloc(sizeof(*tunsec), GFP_KERNEL);
-	if (!tunsec)
-		return -ENOMEM;
 	tunsec->sid = current_sid();
-
-	*security = tunsec;
 	return 0;
 }
 
-static void selinux_tun_dev_free_security(void *security)
-{
-	kfree(security);
-}
-
 static int selinux_tun_dev_create(void)
 {
 	u32 sid = current_sid();
@@ -5613,7 +5603,7 @@ static int selinux_tun_dev_create(void)
 
 static int selinux_tun_dev_attach_queue(void *security)
 {
-	struct tun_security_struct *tunsec = security;
+	struct tun_security_struct *tunsec = selinux_tun_dev(security);
 
 	return avc_has_perm(current_sid(), tunsec->sid, SECCLASS_TUN_SOCKET,
 			    TUN_SOCKET__ATTACH_QUEUE, NULL);
@@ -5621,7 +5611,7 @@ static int selinux_tun_dev_attach_queue(void *security)
 
 static int selinux_tun_dev_attach(struct sock *sk, void *security)
 {
-	struct tun_security_struct *tunsec = security;
+	struct tun_security_struct *tunsec = selinux_tun_dev(security);
 	struct sk_security_struct *sksec = selinux_sock(sk);
 
 	/* we don't currently perform any NetLabel based labeling here and it
@@ -5639,7 +5629,7 @@ static int selinux_tun_dev_attach(struct sock *sk, void *security)
 
 static int selinux_tun_dev_open(void *security)
 {
-	struct tun_security_struct *tunsec = security;
+	struct tun_security_struct *tunsec = selinux_tun_dev(security);
 	u32 sid = current_sid();
 	int err;
 
@@ -6978,6 +6968,7 @@ struct lsm_blob_sizes selinux_blob_sizes __ro_after_init = {
 	.lbs_sock = sizeof(struct sk_security_struct),
 	.lbs_superblock = sizeof(struct superblock_security_struct),
 	.lbs_xattr_count = SELINUX_INODE_INIT_XATTRS,
+	.lbs_tun_dev = sizeof(struct tun_security_struct),
 };
 
 #ifdef CONFIG_PERF_EVENTS
@@ -7289,7 +7280,6 @@ static struct security_hook_list selinux_hooks[] __ro_after_init = {
 	LSM_HOOK_INIT(secmark_refcount_inc, selinux_secmark_refcount_inc),
 	LSM_HOOK_INIT(secmark_refcount_dec, selinux_secmark_refcount_dec),
 	LSM_HOOK_INIT(req_classify_flow, selinux_req_classify_flow),
-	LSM_HOOK_INIT(tun_dev_free_security, selinux_tun_dev_free_security),
 	LSM_HOOK_INIT(tun_dev_create, selinux_tun_dev_create),
 	LSM_HOOK_INIT(tun_dev_attach_queue, selinux_tun_dev_attach_queue),
 	LSM_HOOK_INIT(tun_dev_attach, selinux_tun_dev_attach),

security/selinux/include/objsec.h

@@ -207,4 +207,9 @@ static inline struct sk_security_struct *selinux_sock(const struct sock *sock)
 	return sock->sk_security + selinux_blob_sizes.lbs_sock;
 }
 
+static inline struct tun_security_struct *selinux_tun_dev(void *security)
+{
+	return security + selinux_blob_sizes.lbs_tun_dev;
+}
+
 #endif /* _SELINUX_OBJSEC_H_ */