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, 50 insertions, 0 deletions

diff --git a/Documentation/driver-api/firewire.rst b/Documentation/driver-api/firewire.rst
new file mode 100644
index 000000000..28a32410f
--- /dev/null
+++ b/Documentation/driver-api/firewire.rst
@@ -0,0 +1,50 @@
+===========================================
+Firewire (IEEE 1394) driver Interface Guide
+===========================================
+
+Introduction and Overview
+=========================
+
+The Linux FireWire subsystem adds some interfaces into the Linux system to
+ use/maintain+any resource on IEEE 1394 bus.
+
+The main purpose of these interfaces is to access address space on each node
+on IEEE 1394 bus by ISO/IEC 13213 (IEEE 1212) procedure, and to control
+isochronous resources on the bus by IEEE 1394 procedure.
+
+Two types of interfaces are added, according to consumers of the interface. A
+set of userspace interfaces is available via `firewire character devices`. A set
+of kernel interfaces is available via exported symbols in `firewire-core` module.
+
+Firewire char device data structures
+====================================
+
+.. include:: ../ABI/stable/firewire-cdev
+    :literal:
+
+.. kernel-doc:: include/uapi/linux/firewire-cdev.h
+    :internal:
+
+Firewire device probing and sysfs interfaces
+============================================
+
+.. include:: ../ABI/stable/sysfs-bus-firewire
+    :literal:
+
+.. kernel-doc:: drivers/firewire/core-device.c
+    :export:
+
+Firewire core transaction interfaces
+====================================
+
+.. kernel-doc:: drivers/firewire/core-transaction.c
+    :export:
+
+Firewire Isochronous I/O interfaces
+===================================
+
+.. kernel-doc:: include/linux/firewire.h
+   :functions: fw_iso_context_schedule_flush_completions
+.. kernel-doc:: drivers/firewire/core-iso.c
+   :export:
+