openrisc: fix arbitrary kernel memory access via or1k_atomic syscallgrafted

sys_or1k_atomic() (syscall 244 in the "or1k" ABI) takes two user
pointers, v1 and v2, and swaps the words they point to in hand-written
assembly.

    l.lwz   r29,0(r4)
    l.lwz   r27,0(r5)
    l.sw    0(r4),r27
    l.sw    0(r5),r29

The pointers are not checked with access_ok(). The four memory
accesses also have no exception table entries.

A caller passes a kernel address as either pointer, and the syscall
reads from and writes to it directly.

This gives an unprivileged process a kernel read/write primitive. It
overwrites kernel data such as the sys_call_table, gaining code
execution in kernel context.

Check both pointers before entering the critical section. Add fixups
for the four memory accesses so faults on valid but unmapped user
addresses return -EFAULT.

[shorne@gmail.com: fix comment style]
Fixes: 9d02a4283e9c ("OpenRISC: Boot code")
Cc: stable@vger.kernel.org
Signed-off-by: Ali Ahmet Memis <ali@iusegentoo.com>
Signed-off-by: Stafford Horne <shorne@gmail.com>

1 files changed, 63 insertions, 0 deletions

diff --git a/include/media/media-dev-allocator.h b/include/media/media-dev-allocator.h
new file mode 100644
index 000000000..2ab54d426
--- /dev/null
+++ b/include/media/media-dev-allocator.h
@@ -0,0 +1,63 @@
+/* SPDX-License-Identifier: GPL-2.0+ */
+/*
+ * media-dev-allocator.h - Media Controller Device Allocator API
+ *
+ * Copyright (c) 2019 Shuah Khan <shuah@kernel.org>
+ *
+ * Credits: Suggested by Laurent Pinchart <laurent.pinchart@ideasonboard.com>
+ */
+
+/*
+ * This file adds a global ref-counted Media Controller Device Instance API.
+ * A system wide global media device list is managed and each media device
+ * includes a kref count. The last put on the media device releases the media
+ * device instance.
+ */
+
+#ifndef _MEDIA_DEV_ALLOCATOR_H
+#define _MEDIA_DEV_ALLOCATOR_H
+
+struct usb_device;
+
+#if defined(CONFIG_MEDIA_CONTROLLER) && IS_ENABLED(CONFIG_USB)
+/**
+ * media_device_usb_allocate() - Allocate and return struct &media device
+ *
+ * @udev:		struct &usb_device pointer
+ * @module_name:	should be filled with %KBUILD_MODNAME
+ * @owner:		struct module pointer %THIS_MODULE for the driver.
+ *			%THIS_MODULE is null for a built-in driver.
+ *			It is safe even when %THIS_MODULE is null.
+ *
+ * This interface should be called to allocate a Media Device when multiple
+ * drivers share usb_device and the media device. This interface allocates
+ * &media_device structure and calls media_device_usb_init() to initialize
+ * it.
+ *
+ */
+struct media_device *media_device_usb_allocate(struct usb_device *udev,
+					       const char *module_name,
+					       struct module *owner);
+/**
+ * media_device_delete() - Release media device. Calls kref_put().
+ *
+ * @mdev:		struct &media_device pointer
+ * @module_name:	should be filled with %KBUILD_MODNAME
+ * @owner:		struct module pointer %THIS_MODULE for the driver.
+ *			%THIS_MODULE is null for a built-in driver.
+ *			It is safe even when %THIS_MODULE is null.
+ *
+ * This interface should be called to put Media Device Instance kref.
+ */
+void media_device_delete(struct media_device *mdev, const char *module_name,
+			 struct module *owner);
+#else
+static inline struct media_device *media_device_usb_allocate(
+			struct usb_device *udev, const char *module_name,
+			struct module *owner)
+			{ return NULL; }
+static inline void media_device_delete(
+			struct media_device *mdev, const char *module_name,
+			struct module *owner) { }
+#endif /* CONFIG_MEDIA_CONTROLLER && CONFIG_USB */
+#endif /* _MEDIA_DEV_ALLOCATOR_H */