[PATCH v5 4/4] vduse: Add LSM hook to check Virtio device type

[Maxime Coquelin <maxime.coquelin@redhat.com>]

This patch introduces a LSM hook for devices creation,
destruction (ioctl()) and opening (open()) operations,
checking the application is allowed to perform these
operations for the Virtio device type.

Signed-off-by: Maxime Coquelin <maxime.coquelin@redhat.com>
---
 MAINTAINERS                         |  1 +
 drivers/vdpa/vdpa_user/vduse_dev.c  | 13 ++++++++++++
 include/linux/lsm_hook_defs.h       |  2 ++
 include/linux/security.h            |  6 ++++++
 include/linux/vduse.h               | 14 +++++++++++++
 security/security.c                 | 15 ++++++++++++++
 security/selinux/hooks.c            | 32 +++++++++++++++++++++++++++++
 security/selinux/include/classmap.h |  2 ++
 8 files changed, 85 insertions(+)
 create mode 100644 include/linux/vduse.h

diff --git a/MAINTAINERS b/MAINTAINERS
index a0fb0df07b43..4e83b14358d2 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -23040,6 +23040,7 @@ F:	drivers/net/virtio_net.c
 F:	drivers/vdpa/
 F:	drivers/virtio/
 F:	include/linux/vdpa.h
+F:	include/linux/vduse.h
 F:	include/linux/virtio*.h
 F:	include/linux/vringh.h
 F:	include/uapi/linux/virtio_*.h
diff --git a/drivers/vdpa/vdpa_user/vduse_dev.c b/drivers/vdpa/vdpa_user/vduse_dev.c
index fa62825be378..59ab7eb62e20 100644
--- a/drivers/vdpa/vdpa_user/vduse_dev.c
+++ b/drivers/vdpa/vdpa_user/vduse_dev.c
@@ -8,6 +8,7 @@
  *
  */
 
+#include "linux/security.h"
 #include <linux/init.h>
 #include <linux/module.h>
 #include <linux/cdev.h>
@@ -30,6 +31,7 @@
 #include <uapi/linux/virtio_blk.h>
 #include <uapi/linux/virtio_ring.h>
 #include <linux/mod_devicetable.h>
+#include <linux/vduse.h>
 
 #include "iova_domain.h"
 
@@ -1442,6 +1444,10 @@ static int vduse_dev_open(struct inode *inode, struct file *file)
 	if (dev->connected)
 		goto unlock;
 
+	ret = -EPERM;
+	if (security_vduse_perm_check(VDUSE_PERM_OPEN, dev->device_id))
+		goto unlock;
+
 	ret = 0;
 	dev->connected = true;
 	file->private_data = dev;
@@ -1664,6 +1670,9 @@ static int vduse_destroy_dev(char *name)
 	if (!dev)
 		return -EINVAL;
 
+	if (security_vduse_perm_check(VDUSE_PERM_DESTROY, dev->device_id))
+		return -EPERM;
+
 	mutex_lock(&dev->lock);
 	if (dev->vdev || dev->connected) {
 		mutex_unlock(&dev->lock);
@@ -1828,6 +1837,10 @@ static int vduse_create_dev(struct vduse_dev_config *config,
 	int ret;
 	struct vduse_dev *dev;
 
+	ret = -EPERM;
+	if (security_vduse_perm_check(VDUSE_PERM_CREATE, config->device_id))
+		goto err;
+
 	ret = -EEXIST;
 	if (vduse_find_dev(config->name))
 		goto err;
diff --git a/include/linux/lsm_hook_defs.h b/include/linux/lsm_hook_defs.h
index ff217a5ce552..3930ab2ae974 100644
--- a/include/linux/lsm_hook_defs.h
+++ b/include/linux/lsm_hook_defs.h
@@ -419,3 +419,5 @@ LSM_HOOK(int, 0, uring_override_creds, const struct cred *new)
 LSM_HOOK(int, 0, uring_sqpoll, void)
 LSM_HOOK(int, 0, uring_cmd, struct io_uring_cmd *ioucmd)
 #endif /* CONFIG_IO_URING */
+
+LSM_HOOK(int, 0, vduse_perm_check, enum vduse_op_perm op_perm, u32 device_id)
diff --git a/include/linux/security.h b/include/linux/security.h
index 1d1df326c881..2a2054172394 100644
--- a/include/linux/security.h
+++ b/include/linux/security.h
@@ -32,6 +32,7 @@
 #include <linux/string.h>
 #include <linux/mm.h>
 #include <linux/sockptr.h>
+#include <linux/vduse.h>
 
 struct linux_binprm;
 struct cred;
@@ -484,6 +485,7 @@ int security_inode_notifysecctx(struct inode *inode, void *ctx, u32 ctxlen);
 int security_inode_setsecctx(struct dentry *dentry, void *ctx, u32 ctxlen);
 int security_inode_getsecctx(struct inode *inode, void **ctx, u32 *ctxlen);
 int security_locked_down(enum lockdown_reason what);
+int security_vduse_perm_check(enum vduse_op_perm op_perm, u32 device_id);
 #else /* CONFIG_SECURITY */
 
 static inline int call_blocking_lsm_notifier(enum lsm_event event, void *data)
@@ -1395,6 +1397,10 @@ static inline int security_locked_down(enum lockdown_reason what)
 {
 	return 0;
 }
+static inline int security_vduse_perm_check(enum vduse_op_perm op_perm, u32 device_id)
+{
+	return 0;
+}
 #endif	/* CONFIG_SECURITY */
 
 #if defined(CONFIG_SECURITY) && defined(CONFIG_WATCH_QUEUE)
diff --git a/include/linux/vduse.h b/include/linux/vduse.h
new file mode 100644
index 000000000000..7a20dcc43997
--- /dev/null
+++ b/include/linux/vduse.h
@@ -0,0 +1,14 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _LINUX_VDUSE_H
+#define _LINUX_VDUSE_H
+
+/*
+ * The permission required for a VDUSE device operation.
+ */
+enum vduse_op_perm {
+	VDUSE_PERM_CREATE,
+	VDUSE_PERM_DESTROY,
+	VDUSE_PERM_OPEN,
+};
+
+#endif /* _LINUX_VDUSE_H */
diff --git a/security/security.c b/security/security.c
index dcb3e7014f9b..150abf85f97d 100644
--- a/security/security.c
+++ b/security/security.c
@@ -5337,3 +5337,18 @@ int security_uring_cmd(struct io_uring_cmd *ioucmd)
 	return call_int_hook(uring_cmd, 0, ioucmd);
 }
 #endif /* CONFIG_IO_URING */
+
+/**
+ * security_vduse_perm_check() - Check if a VDUSE device type operation is allowed
+ * @op_perm: the operation type
+ * @device_id: the Virtio device ID
+ *
+ * Check whether the Virtio device creation is allowed
+ *
+ * Return: Returns 0 if permission is granted.
+ */
+int security_vduse_perm_check(enum vduse_op_perm op_perm, u32 device_id)
+{
+	return call_int_hook(vduse_perm_check, 0, op_perm, device_id);
+}
+EXPORT_SYMBOL(security_vduse_perm_check);
diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
index feda711c6b7b..18845e4f682f 100644
--- a/security/selinux/hooks.c
+++ b/security/selinux/hooks.c
@@ -21,6 +21,8 @@
  *  Copyright (C) 2016 Mellanox Technologies
  */
 
+#include "av_permissions.h"
+#include "linux/vduse.h"
 #include <linux/init.h>
 #include <linux/kd.h>
 #include <linux/kernel.h>
@@ -92,6 +94,7 @@
 #include <linux/fsnotify.h>
 #include <linux/fanotify.h>
 #include <linux/io_uring.h>
+#include <uapi/linux/virtio_ids.h>
 
 #include "avc.h"
 #include "objsec.h"
@@ -6950,6 +6953,34 @@ static int selinux_uring_cmd(struct io_uring_cmd *ioucmd)
 }
 #endif /* CONFIG_IO_URING */
 
+static int selinux_vduse_perm_check(enum vduse_op_perm op_perm, u32 device_id)
+{
+	u32 requested_op, requested_type, sid = current_sid();
+	int ret;
+
+	if (op_perm == VDUSE_PERM_CREATE)
+		requested_op = VDUSE__CREATE;
+	else if (op_perm == VDUSE__DESTROY)
+		requested_op = VDUSE__DESTROY;
+	else if (op_perm == VDUSE_PERM_OPEN)
+		requested_op = VDUSE__OPEN;
+	else
+		return -EINVAL;
+
+	ret = avc_has_perm(sid, sid, SECCLASS_VDUSE, requested_op, NULL);
+	if (ret)
+		return ret;
+
+	if (device_id == VIRTIO_ID_NET)
+		requested_type = VDUSE__NET;
+	else if (device_id == VIRTIO_ID_BLOCK)
+		requested_type = VDUSE__BLOCK;
+	else
+		return -EINVAL;
+
+	return avc_has_perm(sid, sid, SECCLASS_VDUSE, requested_type, NULL);
+}
+
 /*
  * IMPORTANT NOTE: When adding new hooks, please be careful to keep this order:
  * 1. any hooks that don't belong to (2.) or (3.) below,
@@ -7243,6 +7274,7 @@ static struct security_hook_list selinux_hooks[] __ro_after_init = {
 #ifdef CONFIG_PERF_EVENTS
 	LSM_HOOK_INIT(perf_event_alloc, selinux_perf_event_alloc),
 #endif
+	LSM_HOOK_INIT(vduse_perm_check, selinux_vduse_perm_check),
 };
 
 static __init int selinux_init(void)
diff --git a/security/selinux/include/classmap.h b/security/selinux/include/classmap.h
index a3c380775d41..b0a358cbac1c 100644
--- a/security/selinux/include/classmap.h
+++ b/security/selinux/include/classmap.h
@@ -256,6 +256,8 @@ const struct security_class_mapping secclass_map[] = {
 	  { "override_creds", "sqpoll", "cmd", NULL } },
 	{ "user_namespace",
 	  { "create", NULL } },
+	{ "vduse",
+	  { "create", "destroy", "open", "net", "block", NULL} },
 	{ NULL }
   };
 
-- 
2.43.0