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, 19 insertions, 0 deletions

diff --git a/net/llc/Makefile b/net/llc/Makefile
new file mode 100644
index 000000000..46b1cd905
--- /dev/null
+++ b/net/llc/Makefile
@@ -0,0 +1,19 @@
+# SPDX-License-Identifier: GPL-2.0
+###########################################################################
+# Makefile for the Linux 802.2 LLC (fully-functional) layer.
+#
+# Copyright (c) 1997 by Procom Technology,Inc.
+#		2001-2003 by Arnaldo Carvalho de Melo <acme@conectiva.com.br>
+###########################################################################
+
+obj-$(CONFIG_LLC) += llc.o
+
+llc-y := llc_core.o llc_input.o llc_output.o
+
+obj-$(CONFIG_LLC2) += llc2.o
+
+llc2-y := llc_if.o llc_c_ev.o llc_c_ac.o llc_conn.o llc_c_st.o llc_pdu.o \
+	  llc_sap.o llc_s_ac.o llc_s_ev.o llc_s_st.o af_llc.o llc_station.o
+
+llc2-$(CONFIG_PROC_FS) += llc_proc.o
+llc2-$(CONFIG_SYSCTL)  += sysctl_net_llc.o