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, 67 insertions, 0 deletions

diff --git a/Documentation/driver-api/w1.rst b/Documentation/driver-api/w1.rst
new file mode 100644
index 000000000..bda3ad60f
--- /dev/null
+++ b/Documentation/driver-api/w1.rst
@@ -0,0 +1,67 @@
+======================
+W1: Dallas' 1-wire bus
+======================
+
+:Author: David Fries
+
+W1 API internal to the kernel
+=============================
+
+include/linux/w1.h
+~~~~~~~~~~~~~~~~~~
+
+W1 kernel API functions.
+
+.. kernel-doc:: include/linux/w1.h
+   :internal:
+
+drivers/w1/w1.c
+~~~~~~~~~~~~~~~
+
+W1 core functions.
+
+.. kernel-doc:: drivers/w1/w1.c
+   :internal:
+
+drivers/w1/w1_family.c
+~~~~~~~~~~~~~~~~~~~~~~~
+
+Allows registering device family operations.
+
+.. kernel-doc:: drivers/w1/w1_family.c
+   :export:
+
+drivers/w1/w1_internal.h
+~~~~~~~~~~~~~~~~~~~~~~~~
+
+W1 internal initialization for master devices.
+
+.. kernel-doc:: drivers/w1/w1_internal.h
+   :internal:
+
+drivers/w1/w1_int.c
+~~~~~~~~~~~~~~~~~~~~
+
+W1 internal initialization for master devices.
+
+.. kernel-doc:: drivers/w1/w1_int.c
+   :export:
+
+drivers/w1/w1_netlink.h
+~~~~~~~~~~~~~~~~~~~~~~~~
+
+W1 external netlink API structures and commands.
+
+.. kernel-doc:: drivers/w1/w1_netlink.h
+   :internal:
+
+drivers/w1/w1_io.c
+~~~~~~~~~~~~~~~~~~~
+
+W1 input/output.
+
+.. kernel-doc:: drivers/w1/w1_io.c
+   :export:
+
+.. kernel-doc:: drivers/w1/w1_io.c
+   :internal: