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, 74 insertions, 0 deletions

diff --git a/Documentation/driver-api/pm/notifiers.rst b/Documentation/driver-api/pm/notifiers.rst
new file mode 100644
index 000000000..186435c43
--- /dev/null
+++ b/Documentation/driver-api/pm/notifiers.rst
@@ -0,0 +1,74 @@
+.. SPDX-License-Identifier: GPL-2.0
+.. include:: <isonum.txt>
+
+=============================
+Suspend/Hibernation Notifiers
+=============================
+
+:Copyright: |copy| 2016 Intel Corporation
+
+:Author: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
+
+
+There are some operations that subsystems or drivers may want to carry out
+before hibernation/suspend or after restore/resume, but they require the system
+to be fully functional, so the drivers' and subsystems' ``->suspend()`` and
+``->resume()`` or even ``->prepare()`` and ``->complete()`` callbacks are not
+suitable for this purpose.
+
+For example, device drivers may want to upload firmware to their devices after
+resume/restore, but they cannot do it by calling :c:func:`request_firmware()`
+from their ``->resume()`` or ``->complete()`` callback routines (user land
+processes are frozen at these points).  The solution may be to load the firmware
+into memory before processes are frozen and upload it from there in the
+``->resume()`` routine.  A suspend/hibernation notifier may be used for that.
+
+Subsystems or drivers having such needs can register suspend notifiers that
+will be called upon the following events by the PM core:
+
+``PM_HIBERNATION_PREPARE``
+	The system is going to hibernate, tasks will be frozen immediately. This
+	is different from ``PM_SUSPEND_PREPARE`` below,	because in this case
+	additional work is done between the notifiers and the invocation of PM
+	callbacks for the "freeze" transition.
+
+``PM_POST_HIBERNATION``
+	The system memory state has been restored from a hibernation image or an
+	error occurred during hibernation.  Device restore callbacks have been
+	executed and tasks have been thawed.
+
+``PM_RESTORE_PREPARE``
+	The system is going to restore a hibernation image.  If all goes well,
+	the restored image kernel will issue a ``PM_POST_HIBERNATION``
+	notification.
+
+``PM_POST_RESTORE``
+	An error occurred during restore from hibernation.  Device restore
+	callbacks have been executed and tasks have been thawed.
+
+``PM_SUSPEND_PREPARE``
+	The system is preparing for suspend.
+
+``PM_POST_SUSPEND``
+	The system has just resumed or an error occurred during suspend.  Device
+	resume callbacks have been executed and tasks have been thawed.
+
+It is generally assumed that whatever the notifiers do for
+``PM_HIBERNATION_PREPARE``, should be undone for ``PM_POST_HIBERNATION``.
+Analogously, operations carried out for ``PM_SUSPEND_PREPARE`` should be
+reversed for ``PM_POST_SUSPEND``.
+
+Moreover, if one of the notifiers fails for the ``PM_HIBERNATION_PREPARE`` or
+``PM_SUSPEND_PREPARE`` event, the notifiers that have already succeeded for that
+event will be called for ``PM_POST_HIBERNATION`` or ``PM_POST_SUSPEND``,
+respectively.
+
+The hibernation and suspend notifiers are called with :c:data:`pm_mutex` held.
+They are defined in the usual way, but their last argument is meaningless (it is
+always NULL).
+
+To register and/or unregister a suspend notifier use
+:c:func:`register_pm_notifier()` and :c:func:`unregister_pm_notifier()`,
+respectively (both defined in :file:`include/linux/suspend.h`).  If you don't
+need to unregister the notifier, you can also use the :c:func:`pm_notifier()`
+macro defined in :file:`include/linux/suspend.h`.