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, 55 insertions, 0 deletions

diff --git a/Documentation/gpu/meson.rst b/Documentation/gpu/meson.rst
new file mode 100644
index 000000000..b9e2f9aa3
--- /dev/null
+++ b/Documentation/gpu/meson.rst
@@ -0,0 +1,55 @@
+=============================================
+drm/meson AmLogic Meson Video Processing Unit
+=============================================
+
+.. kernel-doc:: drivers/gpu/drm/meson/meson_drv.c
+   :doc: Video Processing Unit
+
+Video Processing Unit
+=====================
+
+The Amlogic Meson Display controller is composed of several components
+that are going to be documented below:
+
+.. code::
+
+  DMC|---------------VPU (Video Processing Unit)----------------|------HHI------|
+     | vd1   _______     _____________    _________________     |               |
+  D  |-------|      |----|            |   |                |    |   HDMI PLL    |
+  D  | vd2   | VIU  |    | Video Post |   | Video Encoders |<---|-----VCLK      |
+  R  |-------|      |----| Processing |   |                |    |               |
+     | osd2  |      |    |            |---| Enci ----------|----|-----VDAC------|
+  R  |-------| CSC  |----| Scalers    |   | Encp ----------|----|----HDMI-TX----|
+  A  | osd1  |      |    | Blenders   |   | Encl ----------|----|---------------|
+  M  |-------|______|----|____________|   |________________|    |               |
+  ___|__________________________________________________________|_______________|
+
+Video Input Unit
+================
+
+.. kernel-doc:: drivers/gpu/drm/meson/meson_viu.c
+   :doc: Video Input Unit
+
+Video Post Processing
+=====================
+
+.. kernel-doc:: drivers/gpu/drm/meson/meson_vpp.c
+   :doc: Video Post Processing
+
+Video Encoder
+=============
+
+.. kernel-doc:: drivers/gpu/drm/meson/meson_venc.c
+   :doc: Video Encoder
+
+Video Clocks
+============
+
+.. kernel-doc:: drivers/gpu/drm/meson/meson_vclk.c
+   :doc: Video Clocks
+
+HDMI Video Output
+=================
+
+.. kernel-doc:: drivers/gpu/drm/meson/meson_dw_hdmi.c
+   :doc: HDMI Output