lsm: infrastructure management of the perf_event security blob

Move management of the perf_event->security blob out of the individual
security modules and into the security infrastructure. Instead of
allocating the blobs from within the modules the modules tell the
infrastructure how much space is required, and the space is allocated
there.  There are no longer any modules that require the perf_event_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]
Signed-off-by: Paul Moore <paul@paul-moore.com>

include/linux/lsm_hook_defs.h

@@ -439,7 +439,6 @@ LSM_HOOK(int, 0, locked_down, enum lockdown_reason what)
 #ifdef CONFIG_PERF_EVENTS
 LSM_HOOK(int, 0, perf_event_open, struct perf_event_attr *attr, int type)
 LSM_HOOK(int, 0, perf_event_alloc, struct perf_event *event)
-LSM_HOOK(void, LSM_RET_VOID, perf_event_free, struct perf_event *event)
 LSM_HOOK(int, 0, perf_event_read, struct perf_event *event)
 LSM_HOOK(int, 0, perf_event_write, struct perf_event *event)
 #endif /* CONFIG_PERF_EVENTS */

include/linux/lsm_hooks.h

@@ -79,6 +79,7 @@ struct lsm_blob_sizes {
 	int	lbs_ipc;
 	int	lbs_key;
 	int	lbs_msg_msg;
+	int	lbs_perf_event;
 	int	lbs_task;
 	int	lbs_xattr_count; /* number of xattr slots in new_xattrs array */
 	int	lbs_tun_dev;

security/security.c

@@ -28,6 +28,7 @@
 #include <linux/xattr.h>
 #include <linux/msg.h>
 #include <linux/overflow.h>
+#include <linux/perf_event.h>
 #include <net/flow.h>
 #include <net/sock.h>
 
@@ -230,6 +231,7 @@ static void __init lsm_set_blob_sizes(struct lsm_blob_sizes *needed)
 	lsm_set_blob_size(&needed->lbs_ipc, &blob_sizes.lbs_ipc);
 	lsm_set_blob_size(&needed->lbs_key, &blob_sizes.lbs_key);
 	lsm_set_blob_size(&needed->lbs_msg_msg, &blob_sizes.lbs_msg_msg);
+	lsm_set_blob_size(&needed->lbs_perf_event, &blob_sizes.lbs_perf_event);
 	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);
@@ -412,6 +414,7 @@ static void __init ordered_lsm_init(void)
 	init_debug("msg_msg blob size    = %d\n", blob_sizes.lbs_msg_msg);
 	init_debug("sock blob size       = %d\n", blob_sizes.lbs_sock);
 	init_debug("superblock blob size = %d\n", blob_sizes.lbs_superblock);
+	init_debug("perf event blob size = %d\n", blob_sizes.lbs_perf_event);
 	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);
@@ -5685,7 +5688,19 @@ int security_perf_event_open(struct perf_event_attr *attr, int type)
  */
 int security_perf_event_alloc(struct perf_event *event)
 {
-	return call_int_hook(perf_event_alloc, event);
+	int rc;
+
+	rc = lsm_blob_alloc(&event->security, blob_sizes.lbs_perf_event,
+			    GFP_KERNEL);
+	if (rc)
+		return rc;
+
+	rc = call_int_hook(perf_event_alloc, event);
+	if (rc) {
+		kfree(event->security);
+		event->security = NULL;
+	}
+	return rc;
 }
 
 /**
@@ -5696,7 +5711,8 @@ int security_perf_event_alloc(struct perf_event *event)
  */
 void security_perf_event_free(struct perf_event *event)
 {
-	call_void_hook(perf_event_free, event);
+	kfree(event->security);
+	event->security = NULL;
 }
 
 /**

security/selinux/hooks.c

@@ -6955,6 +6955,9 @@ struct lsm_blob_sizes selinux_blob_sizes __ro_after_init = {
 	.lbs_ipc = sizeof(struct ipc_security_struct),
 	.lbs_key = sizeof(struct key_security_struct),
 	.lbs_msg_msg = sizeof(struct msg_security_struct),
+#ifdef CONFIG_PERF_EVENTS
+	.lbs_perf_event = sizeof(struct perf_event_security_struct),
+#endif
 	.lbs_sock = sizeof(struct sk_security_struct),
 	.lbs_superblock = sizeof(struct superblock_security_struct),
 	.lbs_xattr_count = SELINUX_INODE_INIT_XATTRS,
@@ -6986,24 +6989,12 @@ static int selinux_perf_event_alloc(struct perf_event *event)
 {
 	struct perf_event_security_struct *perfsec;
 
-	perfsec = kzalloc(sizeof(*perfsec), GFP_KERNEL);
-	if (!perfsec)
-		return -ENOMEM;
-
+	perfsec = selinux_perf_event(event->security);
 	perfsec->sid = current_sid();
-	event->security = perfsec;
 
 	return 0;
 }
 
-static void selinux_perf_event_free(struct perf_event *event)
-{
-	struct perf_event_security_struct *perfsec = event->security;
-
-	event->security = NULL;
-	kfree(perfsec);
-}
-
 static int selinux_perf_event_read(struct perf_event *event)
 {
 	struct perf_event_security_struct *perfsec = event->security;
@@ -7316,7 +7307,6 @@ static struct security_hook_list selinux_hooks[] __ro_after_init = {
 
 #ifdef CONFIG_PERF_EVENTS
 	LSM_HOOK_INIT(perf_event_open, selinux_perf_event_open),
-	LSM_HOOK_INIT(perf_event_free, selinux_perf_event_free),
 	LSM_HOOK_INIT(perf_event_read, selinux_perf_event_read),
 	LSM_HOOK_INIT(perf_event_write, selinux_perf_event_write),
 #endif

security/selinux/include/objsec.h

@@ -217,4 +217,10 @@ static inline struct ib_security_struct *selinux_ib(void *ib_sec)
 	return ib_sec + selinux_blob_sizes.lbs_ib;
 }
 
+static inline struct perf_event_security_struct *
+selinux_perf_event(void *perf_event)
+{
+	return perf_event + selinux_blob_sizes.lbs_perf_event;
+}
+
 #endif /* _SELINUX_OBJSEC_H_ */