device_cgroup: Export devcgroup_check_permission

For AMD compute (amdkfd) driver.

All AMD compute devices are exported via single device node /dev/kfd. As
a result devices cannot be controlled individually using device cgroup.

AMD compute devices will rely on its graphics counterpart that exposes
/dev/dri/renderN node for each device. For each task (based on its
cgroup), KFD driver will check if /dev/dri/renderN node is accessible
before exposing it.
Signed-off-by: Harish Kasiviswanathan <Harish.Kasiviswanathan@amd.com>
Acked-by: Tejun Heo <tj@kernel.org>
Acked-by: Felix Kuehling <Felix.Kuehling@amd.com>
Reviewed-by: Roman Gushchin <guro@fb.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

include/linux/device_cgroup.h

@@ -12,26 +12,15 @@
 #define DEVCG_DEV_ALL   4  /* this represents all devices */
 
 #ifdef CONFIG_CGROUP_DEVICE
-extern int __devcgroup_check_permission(short type, u32 major, u32 minor,
-					short access);
+int devcgroup_check_permission(short type, u32 major, u32 minor,
+			       short access);
 #else
-static inline int __devcgroup_check_permission(short type, u32 major, u32 minor,
-					       short access)
+static inline int devcgroup_check_permission(short type, u32 major, u32 minor,
+					     short access)
 { return 0; }
 #endif
 
 #if defined(CONFIG_CGROUP_DEVICE) || defined(CONFIG_CGROUP_BPF)
-static inline int devcgroup_check_permission(short type, u32 major, u32 minor,
-					     short access)
-{
-	int rc = BPF_CGROUP_RUN_PROG_DEVICE_CGROUP(type, major, minor, access);
-
-	if (rc)
-		return -EPERM;
-
-	return __devcgroup_check_permission(type, major, minor, access);
-}
-
 static inline int devcgroup_inode_permission(struct inode *inode, int mask)
 {
 	short type, access = 0;

security/device_cgroup.c

@@ -801,8 +801,8 @@ struct cgroup_subsys devices_cgrp_subsys = {
  *
  * returns 0 on success, -EPERM case the operation is not permitted
  */
-int __devcgroup_check_permission(short type, u32 major, u32 minor,
-				 short access)
+static int __devcgroup_check_permission(short type, u32 major, u32 minor,
+					short access)
 {
 	struct dev_cgroup *dev_cgroup;
 	bool rc;
@@ -824,3 +824,14 @@ int __devcgroup_check_permission(short type, u32 major, u32 minor,
 
 	return 0;
 }
+
+int devcgroup_check_permission(short type, u32 major, u32 minor, short access)
+{
+	int rc = BPF_CGROUP_RUN_PROG_DEVICE_CGROUP(type, major, minor, access);
+
+	if (rc)
+		return -EPERM;
+
+	return __devcgroup_check_permission(type, major, minor, access);
+}
+EXPORT_SYMBOL(devcgroup_check_permission);