[PATCH v2 4/6] LSM: Infrastructure management of the dev_tun blob

[Casey Schaufler <casey@schaufler-ca.com>]

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>
---
 include/linux/lsm_hook_defs.h     |  3 +--
 include/linux/lsm_hooks.h         |  1 +
 security/security.c               | 17 +++++++++++++++--
 security/selinux/hooks.c          | 22 ++++++----------------
 security/selinux/include/objsec.h |  6 ++++++
 5 files changed, 29 insertions(+), 20 deletions(-)

diff --git a/include/linux/lsm_hook_defs.h b/include/linux/lsm_hook_defs.h
index cc81f7f7c024..f1e0d6138845 100644
--- a/include/linux/lsm_hook_defs.h
+++ b/include/linux/lsm_hook_defs.h
@@ -352,8 +352,7 @@ 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)
diff --git a/include/linux/lsm_hooks.h b/include/linux/lsm_hooks.h
index 7233bc0737be..0ff14ff128c8 100644
--- a/include/linux/lsm_hooks.h
+++ b/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;
 };
 
 /**
diff --git a/security/security.c b/security/security.c
index e5af4274b8aa..f1eb93b65ae9 100644
--- a/security/security.c
+++ b/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);
 
 	/*
@@ -4849,7 +4851,18 @@ 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);
 
@@ -4861,7 +4874,7 @@ 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);
 
diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
index 986825ba1cc5..34ed787a4bfa 100644
--- a/security/selinux/hooks.c
+++ b/security/selinux/hooks.c
@@ -5573,24 +5573,14 @@ 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();
@@ -5608,7 +5598,7 @@ 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);
@@ -5616,7 +5606,7 @@ 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
@@ -5634,7 +5624,7 @@ 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;
 
@@ -6973,6 +6963,7 @@ 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
@@ -7283,7 +7274,6 @@ 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),
diff --git a/security/selinux/include/objsec.h b/security/selinux/include/objsec.h
index 83b9443d6919..461c6985977d 100644
--- a/security/selinux/include/objsec.h
+++ b/security/selinux/include/objsec.h
@@ -207,4 +207,10 @@ 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_ */
-- 
2.45.2