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, 33 insertions, 0 deletions

diff --git a/Documentation/ABI/testing/devlink-resource-mlxsw b/Documentation/ABI/testing/devlink-resource-mlxsw
new file mode 100644
index 000000000..259ed2948
--- /dev/null
+++ b/Documentation/ABI/testing/devlink-resource-mlxsw
@@ -0,0 +1,33 @@
+What: 		/kvd/
+Date:		08-Jan-2018
+KernelVersion:	v4.16
+Contact:	mlxsw@mellanox.com
+Description:	The main database in the Spectrum device is a centralized
+		KVD database used for many of the tables used to configure
+		the chip including L2 FDB, L3 LPM, ECMP and more. The KVD
+		is divided into two sections, the first is hash-based table
+		and the second is a linear access table. The division
+		between the linear and hash-based sections is static and
+		require reload before the changes take effect.
+
+What: 		/kvd/linear
+Date:		08-Jan-2018
+KernelVersion:	v4.16
+Contact:	mlxsw@mellanox.com
+Description:	The linear section of the KVD is managed by software as a
+		flat memory accessed using an index.
+
+What: 		/kvd/hash_single
+Date:		08-Jan-2018
+KernelVersion:	v4.16
+Contact:	mlxsw@mellanox.com
+Description:	The hash based section of the KVD is managed by the switch
+		device. Used in case the key size is smaller or equal to
+		64bit.
+
+What: 		/kvd/hash_double
+Date:		08-Jan-2018
+KernelVersion:	v4.16
+Contact:	mlxsw@mellanox.com
+Description:	The hash based section of the KVD is managed by the switch
+		device. Used in case the key is larger than 64 bit.