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, 76 insertions, 0 deletions

diff --git a/Documentation/ABI/testing/sysfs-class-wakeup b/Documentation/ABI/testing/sysfs-class-wakeup
new file mode 100644
index 000000000..754aab8b6
--- /dev/null
+++ b/Documentation/ABI/testing/sysfs-class-wakeup
@@ -0,0 +1,76 @@
+What:		/sys/class/wakeup/
+Date:		June 2019
+Contact:	Tri Vo <trong@android.com>
+Description:
+		The /sys/class/wakeup/ directory contains pointers to all
+		wakeup sources in the kernel at that moment in time.
+
+What:		/sys/class/wakeup/.../name
+Date:		June 2019
+Contact:	Tri Vo <trong@android.com>
+Description:
+		This file contains the name of the wakeup source.
+
+What:		/sys/class/wakeup/.../active_count
+Date:		June 2019
+Contact:	Tri Vo <trong@android.com>
+Description:
+		This file contains the number of times the wakeup source was
+		activated.
+
+What:		/sys/class/wakeup/.../event_count
+Date:		June 2019
+Contact:	Tri Vo <trong@android.com>
+Description:
+		This file contains the number of signaled wakeup events
+		associated with the wakeup source.
+
+What:		/sys/class/wakeup/.../wakeup_count
+Date:		June 2019
+Contact:	Tri Vo <trong@android.com>
+Description:
+		This file contains the number of times the wakeup source might
+		abort suspend.
+
+What:		/sys/class/wakeup/.../expire_count
+Date:		June 2019
+Contact:	Tri Vo <trong@android.com>
+Description:
+		This file contains the number of times the wakeup source's
+		timeout has expired.
+
+What:		/sys/class/wakeup/.../active_time_ms
+Date:		June 2019
+Contact:	Tri Vo <trong@android.com>
+Description:
+		This file contains the amount of time the wakeup source has
+		been continuously active, in milliseconds.  If the wakeup
+		source is not active, this file contains '0'.
+
+What:		/sys/class/wakeup/.../total_time_ms
+Date:		June 2019
+Contact:	Tri Vo <trong@android.com>
+Description:
+		This file contains the total amount of time this wakeup source
+		has been active, in milliseconds.
+
+What:		/sys/class/wakeup/.../max_time_ms
+Date:		June 2019
+Contact:	Tri Vo <trong@android.com>
+Description:
+		This file contains the maximum amount of time this wakeup
+		source has been continuously active, in milliseconds.
+
+What:		/sys/class/wakeup/.../last_change_ms
+Date:		June 2019
+Contact:	Tri Vo <trong@android.com>
+Description:
+		This file contains the monotonic clock time when the wakeup
+		source was touched last time, in milliseconds.
+
+What:		/sys/class/wakeup/.../prevent_suspend_time_ms
+Date:		June 2019
+Contact:	Tri Vo <trong@android.com>
+Description:
+		The file contains the total amount of time this wakeup source
+		has been preventing autosleep, in milliseconds.