[PATCH 6/6] LSM: Infrastructure management of the perf_event security blob

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

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.

Signed-off-by: Casey Schaufler <casey@schaufler-ca.com>
---
 include/linux/lsm_hooks.h         |  1 +
 security/security.c               | 12 ++++++++++++
 security/selinux/hooks.c          | 18 ++++--------------
 security/selinux/include/objsec.h |  6 ++++++
 4 files changed, 23 insertions(+), 14 deletions(-)

diff --git a/include/linux/lsm_hooks.h b/include/linux/lsm_hooks.h
index b6fc6ac88723..f1ca8082075a 100644
--- a/include/linux/lsm_hooks.h
+++ b/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;
diff --git a/security/security.c b/security/security.c
index 731a54fabc79..da2111f8d9df 100644
--- a/security/security.c
+++ b/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>
 
@@ -232,6 +233,7 @@ static void __init lsm_set_blob_sizes(struct lsm_blob_sizes *needed)
 	lsm_set_blob_size(&needed->lbs_key, &blob_sizes.lbs_key);
 #endif
 	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);
@@ -414,6 +416,7 @@ 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);
@@ -5653,6 +5656,13 @@ int security_perf_event_open(struct perf_event_attr *attr, int type)
  */
 int security_perf_event_alloc(struct perf_event *event)
 {
+	int rc;
+
+	rc = lsm_blob_alloc(&event->security, blob_sizes.lbs_perf_event,
+			    GFP_KERNEL);
+	if (rc)
+		return rc;
+
 	return call_int_hook(perf_event_alloc, event);
 }
 
@@ -5665,6 +5675,8 @@ 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;
 }
 
 /**
diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
index 79fe75603881..d1d6adfdfbc7 100644
--- a/security/selinux/hooks.c
+++ b/security/selinux/hooks.c
@@ -6952,6 +6952,9 @@ struct lsm_blob_sizes selinux_blob_sizes __ro_after_init = {
 	.lbs_key = sizeof(struct key_security_struct),
 #endif /* CONFIG_KEYS */
 	.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,
@@ -6983,24 +6986,12 @@ 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;
@@ -7312,7 +7303,6 @@ 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
diff --git a/security/selinux/include/objsec.h b/security/selinux/include/objsec.h
index b1878f9395b5..d632a9180b41 100644
--- a/security/selinux/include/objsec.h
+++ b/security/selinux/include/objsec.h
@@ -219,4 +219,10 @@ 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_ */
-- 
2.41.0