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, 88 insertions, 0 deletions

diff --git a/arch/powerpc/boot/ebony.c b/arch/powerpc/boot/ebony.c
new file mode 100644
index 000000000..add2316d3
--- /dev/null
+++ b/arch/powerpc/boot/ebony.c
@@ -0,0 +1,88 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Copyright 2007 David Gibson, IBM Corporation.
+ *
+ * Based on earlier code:
+ *   Copyright (C) Paul Mackerras 1997.
+ *
+ *   Matt Porter <mporter@kernel.crashing.org>
+ *   Copyright 2002-2005 MontaVista Software Inc.
+ *
+ *   Eugene Surovegin <eugene.surovegin@zultys.com> or <ebs@ebshome.net>
+ *   Copyright (c) 2003, 2004 Zultys Technologies
+ */
+#include <stdarg.h>
+#include <stddef.h>
+#include "types.h"
+#include "elf.h"
+#include "string.h"
+#include "stdio.h"
+#include "page.h"
+#include "ops.h"
+#include "reg.h"
+#include "io.h"
+#include "dcr.h"
+#include "4xx.h"
+#include "44x.h"
+
+static u8 *ebony_mac0, *ebony_mac1;
+
+#define EBONY_FPGA_PATH		"/plb/opb/ebc/fpga"
+#define	EBONY_FPGA_FLASH_SEL	0x01
+#define EBONY_SMALL_FLASH_PATH	"/plb/opb/ebc/small-flash"
+
+static void ebony_flashsel_fixup(void)
+{
+	void *devp;
+	u32 reg[3] = {0x0, 0x0, 0x80000};
+	u8 *fpga;
+	u8 fpga_reg0 = 0x0;
+
+	devp = finddevice(EBONY_FPGA_PATH);
+	if (!devp)
+		fatal("Couldn't locate FPGA node %s\n\r", EBONY_FPGA_PATH);
+
+	if (getprop(devp, "virtual-reg", &fpga, sizeof(fpga)) != sizeof(fpga))
+		fatal("%s has missing or invalid virtual-reg property\n\r",
+		      EBONY_FPGA_PATH);
+
+	fpga_reg0 = in_8(fpga);
+
+	devp = finddevice(EBONY_SMALL_FLASH_PATH);
+	if (!devp)
+		fatal("Couldn't locate small flash node %s\n\r",
+		      EBONY_SMALL_FLASH_PATH);
+
+	if (getprop(devp, "reg", reg, sizeof(reg)) != sizeof(reg))
+		fatal("%s has reg property of unexpected size\n\r",
+		      EBONY_SMALL_FLASH_PATH);
+
+	/* Invert address bit 14 (IBM-endian) if FLASH_SEL fpga bit is set */
+	if (fpga_reg0 & EBONY_FPGA_FLASH_SEL)
+		reg[1] ^= 0x80000;
+
+	setprop(devp, "reg", reg, sizeof(reg));
+}
+
+static void ebony_fixups(void)
+{
+	// FIXME: sysclk should be derived by reading the FPGA registers
+	unsigned long sysclk = 33000000;
+
+	ibm440gp_fixup_clocks(sysclk, 6 * 1843200);
+	ibm4xx_sdram_fixup_memsize();
+	dt_fixup_mac_address_by_alias("ethernet0", ebony_mac0);
+	dt_fixup_mac_address_by_alias("ethernet1", ebony_mac1);
+	ibm4xx_fixup_ebc_ranges("/plb/opb/ebc");
+	ebony_flashsel_fixup();
+}
+
+void ebony_init(void *mac0, void *mac1)
+{
+	platform_ops.fixups = ebony_fixups;
+	platform_ops.exit = ibm44x_dbcr_reset;
+	ebony_mac0 = mac0;
+	ebony_mac1 = mac1;
+	fdt_init(_dtb_start);
+	serial_console_init();
+}