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, 41 insertions, 0 deletions

diff --git a/arch/arm/mach-s3c/dev-uart.c b/arch/arm/mach-s3c/dev-uart.c
new file mode 100644
index 000000000..3d1f7f2fd
--- /dev/null
+++ b/arch/arm/mach-s3c/dev-uart.c
@@ -0,0 +1,41 @@
+// SPDX-License-Identifier: GPL-2.0
+//
+//	originally from arch/arm/plat-s3c24xx/devs.c
+//
+// Copyright (c) 2004 Simtec Electronics
+//	Ben Dooks <ben@simtec.co.uk>
+//
+// Base S3C24XX platform device definitions
+
+#include <linux/kernel.h>
+#include <linux/platform_device.h>
+
+#include "devs.h"
+
+/* uart devices */
+
+static struct platform_device s3c24xx_uart_device0 = {
+	.id		= 0,
+};
+
+static struct platform_device s3c24xx_uart_device1 = {
+	.id		= 1,
+};
+
+static struct platform_device s3c24xx_uart_device2 = {
+	.id		= 2,
+};
+
+static struct platform_device s3c24xx_uart_device3 = {
+	.id		= 3,
+};
+
+struct platform_device *s3c24xx_uart_src[4] = {
+	&s3c24xx_uart_device0,
+	&s3c24xx_uart_device1,
+	&s3c24xx_uart_device2,
+	&s3c24xx_uart_device3,
+};
+
+struct platform_device *s3c24xx_uart_devs[4] = {
+};