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, 23 insertions, 0 deletions

diff --git a/drivers/video/Makefile b/drivers/video/Makefile
new file mode 100644
index 000000000..ffbac4387
--- /dev/null
+++ b/drivers/video/Makefile
@@ -0,0 +1,23 @@
+# SPDX-License-Identifier: GPL-2.0
+
+obj-$(CONFIG_APERTURE_HELPERS)    += aperture.o
+obj-$(CONFIG_SCREEN_INFO)         += screen_info.o
+obj-$(CONFIG_STI_CORE)            += sticore.o
+obj-$(CONFIG_VGASTATE)            += vgastate.o
+obj-$(CONFIG_VIDEO)               += cmdline.o nomodeset.o
+obj-$(CONFIG_HDMI)                += hdmi.o
+
+screen_info-y			  := screen_info_generic.o
+screen_info-$(CONFIG_PCI)         += screen_info_pci.o
+
+obj-$(CONFIG_VT)		  += console/
+obj-$(CONFIG_FB_STI)		  += console/
+obj-$(CONFIG_LOGO)		  += logo/
+obj-y				  += backlight/
+
+obj-y				  += fbdev/
+
+obj-$(CONFIG_VIDEOMODE_HELPERS) += display_timing.o videomode.o
+ifeq ($(CONFIG_OF),y)
+obj-$(CONFIG_VIDEOMODE_HELPERS) += of_display_timing.o of_videomode.o
+endif