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, 49 insertions, 0 deletions

diff --git a/include/sound/sof/xtensa.h b/include/sound/sof/xtensa.h
new file mode 100644
index 000000000..ef70f8e26
--- /dev/null
+++ b/include/sound/sof/xtensa.h
@@ -0,0 +1,49 @@
+/* SPDX-License-Identifier: (GPL-2.0-only OR BSD-3-Clause) */
+/*
+ * This file is provided under a dual BSD/GPLv2 license.  When using or
+ * redistributing this file, you may do so under either license.
+ *
+ * Copyright(c) 2018 Intel Corporation
+ */
+
+#ifndef __INCLUDE_SOUND_SOF_XTENSA_H__
+#define __INCLUDE_SOUND_SOF_XTENSA_H__
+
+#include <sound/sof/header.h>
+
+/*
+ * Architecture specific debug
+ */
+
+/* Xtensa Firmware Oops data */
+struct sof_ipc_dsp_oops_xtensa {
+	struct sof_ipc_dsp_oops_arch_hdr arch_hdr;
+	struct sof_ipc_dsp_oops_plat_hdr plat_hdr;
+	uint32_t exccause;
+	uint32_t excvaddr;
+	uint32_t ps;
+	uint32_t epc1;
+	uint32_t epc2;
+	uint32_t epc3;
+	uint32_t epc4;
+	uint32_t epc5;
+	uint32_t epc6;
+	uint32_t epc7;
+	uint32_t eps2;
+	uint32_t eps3;
+	uint32_t eps4;
+	uint32_t eps5;
+	uint32_t eps6;
+	uint32_t eps7;
+	uint32_t depc;
+	uint32_t intenable;
+	uint32_t interrupt;
+	uint32_t sar;
+	uint32_t debugcause;
+	uint32_t windowbase;
+	uint32_t windowstart;
+	uint32_t excsave1;
+	uint32_t ar[];
+}  __packed;
+
+#endif