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, 37 insertions, 0 deletions

diff --git a/include/soc/imx/cpu.h b/include/soc/imx/cpu.h
new file mode 100644
index 000000000..0bf610aca
--- /dev/null
+++ b/include/soc/imx/cpu.h
@@ -0,0 +1,37 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+
+#ifndef __IMX_CPU_H__
+#define __IMX_CPU_H__
+
+#define MXC_CPU_MX1		1
+#define MXC_CPU_MX21		21
+#define MXC_CPU_MX25		25
+#define MXC_CPU_MX27		27
+#define MXC_CPU_MX31		31
+#define MXC_CPU_MX35		35
+#define MXC_CPU_MX50		50
+#define MXC_CPU_MX51		51
+#define MXC_CPU_MX53		53
+#define MXC_CPU_IMX6SL		0x60
+#define MXC_CPU_IMX6DL		0x61
+#define MXC_CPU_IMX6SX		0x62
+#define MXC_CPU_IMX6Q		0x63
+#define MXC_CPU_IMX6UL		0x64
+#define MXC_CPU_IMX6ULL		0x65
+/* virtual cpu id for i.mx6ulz */
+#define MXC_CPU_IMX6ULZ		0x6b
+#define MXC_CPU_IMX6SLL		0x67
+#define MXC_CPU_IMX7D		0x72
+#define MXC_CPU_IMX7ULP		0xff
+
+#define MXC_CPU_VFx10		0x010
+#define MXC_CPU_VF500		0x500
+#define MXC_CPU_VF510		(MXC_CPU_VF500 | MXC_CPU_VFx10)
+#define MXC_CPU_VF600		0x600
+#define MXC_CPU_VF610		(MXC_CPU_VF600 | MXC_CPU_VFx10)
+
+#ifndef __ASSEMBLY__
+extern unsigned int __mxc_cpu_type;
+#endif
+
+#endif