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, 22 insertions, 0 deletions

diff --git a/net/can/Makefile b/net/can/Makefile
new file mode 100644
index 000000000..58f2c31c1
--- /dev/null
+++ b/net/can/Makefile
@@ -0,0 +1,22 @@
+# SPDX-License-Identifier: GPL-2.0
+#
+#  Makefile for the Linux Controller Area Network core.
+#
+
+obj-$(CONFIG_CAN)	+= can.o
+can-y			:= af_can.o
+can-$(CONFIG_PROC_FS)	+= proc.o
+
+obj-$(CONFIG_CAN_RAW)	+= can-raw.o
+can-raw-y		:= raw.o
+
+obj-$(CONFIG_CAN_BCM)	+= can-bcm.o
+can-bcm-y		:= bcm.o
+
+obj-$(CONFIG_CAN_GW)	+= can-gw.o
+can-gw-y		:= gw.o
+
+obj-$(CONFIG_CAN_J1939)	+= j1939/
+
+obj-$(CONFIG_CAN_ISOTP)	+= can-isotp.o
+can-isotp-y		:= isotp.o