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, 45 insertions, 0 deletions

diff --git a/Documentation/ABI/testing/sysfs-block-aoe b/Documentation/ABI/testing/sysfs-block-aoe
new file mode 100644
index 000000000..b5837765b
--- /dev/null
+++ b/Documentation/ABI/testing/sysfs-block-aoe
@@ -0,0 +1,45 @@
+What:		/sys/block/etherd*/mac
+Date:		Apr, 2005
+KernelVersion:	v2.6.12
+Contact:	Ed L. Cashin <ed.cashin@acm.org>
+Description:
+		(RO) The ethernet address of the remote Ata over Ethernet (AoE)
+		device.
+
+What:		/sys/block/etherd*/netif
+Date:		Apr, 2005
+KernelVersion:	v2.6.12
+Contact:	Ed L. Cashin <ed.cashin@acm.org>
+Description:
+		(RO) The names of the network interfaces on the localhost (comma
+		separated) through which we are communicating with the remote
+		AoE device.
+
+What:		/sys/block/etherd*/state
+Date:		Apr, 2005
+KernelVersion:	v2.6.12
+Contact:	Ed L. Cashin <ed.cashin@acm.org>
+Description:
+		(RO) Device status. The state attribute is "up" when the device
+		is ready for I/O and "down" if detected but unusable. The
+		"down,closewait" state shows that the device is still open and
+		cannot come up again until it has been closed.  The "up,kickme"
+		state means that the driver wants to send more commands to the
+		target but found out there were already the max number of
+		commands waiting for a response. It will retry again after being
+		kicked by the periodic timer handler routine.
+
+What:		/sys/block/etherd*/firmware-version
+Date:		Apr, 2005
+KernelVersion:	v2.6.12
+Contact:	Ed L. Cashin <ed.cashin@acm.org>
+Description:
+		(RO) Version of the firmware in the target.
+
+What:		/sys/block/etherd*/payload
+Date:		Dec, 2012
+KernelVersion:	v3.10
+Contact:	Ed L. Cashin <ed.cashin@acm.org>
+Description:
+		(RO) The amount of user data transferred (in bytes) inside each AoE
+		command on the network, network headers excluded.