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, 21 insertions, 0 deletions

diff --git a/Documentation/ABI/testing/sysfs-driver-intel-rapid-start b/Documentation/ABI/testing/sysfs-driver-intel-rapid-start
new file mode 100644
index 000000000..5a7d2e217
--- /dev/null
+++ b/Documentation/ABI/testing/sysfs-driver-intel-rapid-start
@@ -0,0 +1,21 @@
+What:		/sys/bus/acpi/intel-rapid-start/wakeup_events
+Date:		July 2, 2013
+KernelVersion:	3.11
+Contact:	Matthew Garrett <mjg59@srcf.ucam.org>
+Description:	An integer representing a set of wakeup events as follows:
+		1: Wake to enter hibernation when the wakeup timer expires
+		2: Wake to enter hibernation when the battery reaches a
+		critical level
+
+		These values are ORed together. For example, a value of 3
+		indicates that the system will wake to enter hibernation when
+		either the wakeup timer expires or the battery reaches a
+		critical level.
+
+What:		/sys/bus/acpi/intel-rapid-start/wakeup_time
+Date:		July 2, 2013
+KernelVersion:	3.11
+Contact:	Matthew Garrett <mjg59@srcf.ucam.org>
+Description:	An integer representing the length of time the system will
+		remain asleep before waking up to enter hibernation.
+		This value is in minutes.