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, 164 insertions, 0 deletions

diff --git a/arch/mips/n64/init.c b/arch/mips/n64/init.c
new file mode 100644
index 000000000..66ec28ab4
--- /dev/null
+++ b/arch/mips/n64/init.c
@@ -0,0 +1,164 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ *  Nintendo 64 init.
+ *
+ *  Copyright (C) 2021	Lauri Kasanen
+ */
+#include <linux/init.h>
+#include <linux/ioport.h>
+#include <linux/irq.h>
+#include <linux/memblock.h>
+#include <linux/platform_device.h>
+#include <linux/platform_data/simplefb.h>
+#include <linux/string.h>
+
+#include <asm/bootinfo.h>
+#include <asm/fw/fw.h>
+#include <asm/time.h>
+
+#define IO_MEM_RESOURCE_START	0UL
+#define IO_MEM_RESOURCE_END	0x1fffffffUL
+
+/*
+ * System-specifc irq names for clarity
+ */
+#define MIPS_CPU_IRQ(x)		(MIPS_CPU_IRQ_BASE + (x))
+#define MIPS_SOFTINT0_IRQ	MIPS_CPU_IRQ(0)
+#define MIPS_SOFTINT1_IRQ	MIPS_CPU_IRQ(1)
+#define RCP_IRQ			MIPS_CPU_IRQ(2)
+#define CART_IRQ		MIPS_CPU_IRQ(3)
+#define PRENMI_IRQ		MIPS_CPU_IRQ(4)
+#define RDBR_IRQ		MIPS_CPU_IRQ(5)
+#define RDBW_IRQ		MIPS_CPU_IRQ(6)
+#define TIMER_IRQ		MIPS_CPU_IRQ(7)
+
+static void __init iomem_resource_init(void)
+{
+	iomem_resource.start = IO_MEM_RESOURCE_START;
+	iomem_resource.end = IO_MEM_RESOURCE_END;
+}
+
+const char *get_system_type(void)
+{
+	return "Nintendo 64";
+}
+
+void __init prom_init(void)
+{
+	fw_init_cmdline();
+}
+
+#define W 320
+#define H 240
+#define REG_BASE ((u32 __iomem *) CKSEG1ADDR(0x4400000))
+
+static void __init n64rdp_write_reg(const u8 reg, const u32 value)
+{
+	__raw_writel(value, REG_BASE + reg);
+}
+
+#undef REG_BASE
+
+static const u32 ntsc_320[] __initconst = {
+	0x00013212, 0x00000000, 0x00000140, 0x00000200,
+	0x00000000, 0x03e52239, 0x0000020d, 0x00000c15,
+	0x0c150c15, 0x006c02ec, 0x002501ff, 0x000e0204,
+	0x00000200, 0x00000400
+};
+
+#define MI_REG_BASE 0x4300000
+#define NUM_MI_REGS 4
+#define AI_REG_BASE 0x4500000
+#define NUM_AI_REGS 6
+#define PI_REG_BASE 0x4600000
+#define NUM_PI_REGS 5
+#define SI_REG_BASE 0x4800000
+#define NUM_SI_REGS 7
+
+static int __init n64_platform_init(void)
+{
+	static const char simplefb_resname[] = "FB";
+	static const struct simplefb_platform_data mode = {
+		.width = W,
+		.height = H,
+		.stride = W * 2,
+		.format = "r5g5b5a1"
+	};
+	struct resource res[3];
+	void *orig;
+	unsigned long phys;
+	unsigned i;
+
+	memset(res, 0, sizeof(struct resource) * 3);
+	res[0].flags = IORESOURCE_MEM;
+	res[0].start = MI_REG_BASE;
+	res[0].end = MI_REG_BASE + NUM_MI_REGS * 4 - 1;
+
+	res[1].flags = IORESOURCE_MEM;
+	res[1].start = AI_REG_BASE;
+	res[1].end = AI_REG_BASE + NUM_AI_REGS * 4 - 1;
+
+	res[2].flags = IORESOURCE_IRQ;
+	res[2].start = RCP_IRQ;
+	res[2].end = RCP_IRQ;
+
+	platform_device_register_simple("n64audio", -1, res, 3);
+
+	memset(&res[0], 0, sizeof(res[0]));
+	res[0].flags = IORESOURCE_MEM;
+	res[0].start = PI_REG_BASE;
+	res[0].end = PI_REG_BASE + NUM_PI_REGS * 4 - 1;
+
+	platform_device_register_simple("n64cart", -1, res, 1);
+
+	memset(&res[0], 0, sizeof(res[0]));
+	res[0].flags = IORESOURCE_MEM;
+	res[0].start = SI_REG_BASE;
+	res[0].end = SI_REG_BASE + NUM_SI_REGS * 4 - 1;
+
+	platform_device_register_simple("n64joy", -1, res, 1);
+
+	/* The framebuffer needs 64-byte alignment */
+	orig = kzalloc(W * H * 2 + 63, GFP_DMA | GFP_KERNEL);
+	if (!orig)
+		return -ENOMEM;
+	phys = virt_to_phys(orig);
+	phys += 63;
+	phys &= ~63;
+
+	for (i = 0; i < ARRAY_SIZE(ntsc_320); i++) {
+		if (i == 1)
+			n64rdp_write_reg(i, phys);
+		else
+			n64rdp_write_reg(i, ntsc_320[i]);
+	}
+
+	/* setup IORESOURCE_MEM as framebuffer memory */
+	memset(&res[0], 0, sizeof(res[0]));
+	res[0].flags = IORESOURCE_MEM;
+	res[0].name = simplefb_resname;
+	res[0].start = phys;
+	res[0].end = phys + W * H * 2 - 1;
+
+	platform_device_register_resndata(NULL, "simple-framebuffer", 0,
+					  &res[0], 1, &mode, sizeof(mode));
+
+	return 0;
+}
+
+#undef W
+#undef H
+
+arch_initcall(n64_platform_init);
+
+void __init plat_mem_setup(void)
+{
+	iomem_resource_init();
+	memblock_add(0x0, 8 * 1024 * 1024); /* Bootloader blocks the 4mb config */
+}
+
+void __init plat_time_init(void)
+{
+	/* 93.75 MHz cpu, count register runs at half rate */
+	mips_hpt_frequency = 93750000 / 2;
+}