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, 26 insertions, 0 deletions

diff --git a/Documentation/admin-guide/media/c3-isp.dot b/Documentation/admin-guide/media/c3-isp.dot
new file mode 100644
index 000000000..42dc931ee
--- /dev/null
+++ b/Documentation/admin-guide/media/c3-isp.dot
@@ -0,0 +1,26 @@
+digraph board {
+	rankdir=TB
+	n00000001 [label="{{<port0> 0 | <port1> 1} | c3-isp-core\n/dev/v4l-subdev0 | {<port2> 2 | <port3> 3 | <port4> 4 | <port5> 5}}", shape=Mrecord, style=filled, fillcolor=green]
+	n00000001:port3 -> n00000008:port0
+	n00000001:port4 -> n0000000b:port0
+	n00000001:port5 -> n0000000e:port0
+	n00000001:port2 -> n00000027
+	n00000008 [label="{{<port0> 0} | c3-isp-resizer0\n/dev/v4l-subdev1 | {<port1> 1}}", shape=Mrecord, style=filled, fillcolor=green]
+	n00000008:port1 -> n00000016 [style=bold]
+	n0000000b [label="{{<port0> 0} | c3-isp-resizer1\n/dev/v4l-subdev2 | {<port1> 1}}", shape=Mrecord, style=filled, fillcolor=green]
+	n0000000b:port1 -> n0000001a [style=bold]
+	n0000000e [label="{{<port0> 0} | c3-isp-resizer2\n/dev/v4l-subdev3 | {<port1> 1}}", shape=Mrecord, style=filled, fillcolor=green]
+	n0000000e:port1 -> n00000023 [style=bold]
+	n00000011 [label="{{<port0> 0} | c3-mipi-adapter\n/dev/v4l-subdev4 | {<port1> 1}}", shape=Mrecord, style=filled, fillcolor=green]
+	n00000011:port1 -> n00000001:port0 [style=bold]
+	n00000016 [label="c3-isp-cap0\n/dev/video0", shape=box, style=filled, fillcolor=yellow]
+	n0000001a [label="c3-isp-cap1\n/dev/video1", shape=box, style=filled, fillcolor=yellow]
+	n0000001e [label="{{<port0> 0} | c3-mipi-csi2\n/dev/v4l-subdev5 | {<port1> 1}}", shape=Mrecord, style=filled, fillcolor=green]
+	n0000001e:port1 -> n00000011:port0 [style=bold]
+	n00000023 [label="c3-isp-cap2\n/dev/video2", shape=box, style=filled, fillcolor=yellow]
+	n00000027 [label="c3-isp-stats\n/dev/video3", shape=box, style=filled, fillcolor=yellow]
+	n0000002b [label="c3-isp-params\n/dev/video4", shape=box, style=filled, fillcolor=yellow]
+	n0000002b -> n00000001:port1
+	n0000003f [label="{{} | imx290 2-001a\n/dev/v4l-subdev6 | {<port0> 0}}", shape=Mrecord, style=filled, fillcolor=green]
+	n0000003f:port0 -> n0000001e:port0 [style=bold]
+}