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/drivers/mfd/ocelot.h b/drivers/mfd/ocelot.h
new file mode 100644
index 000000000..b8bc2f148
--- /dev/null
+++ b/drivers/mfd/ocelot.h
@@ -0,0 +1,49 @@
+/* SPDX-License-Identifier: GPL-2.0 OR MIT */
+/* Copyright 2021, 2022 Innovative Advantage Inc. */
+
+#ifndef _MFD_OCELOT_H
+#define _MFD_OCELOT_H
+
+#include <linux/kconfig.h>
+
+struct device;
+struct regmap;
+struct resource;
+
+/**
+ * struct ocelot_ddata - Private data for an external Ocelot chip
+ * @gcb_regmap:		General Configuration Block regmap. Used for
+ *			operations like chip reset.
+ * @cpuorg_regmap:	CPU Device Origin Block regmap. Used for operations
+ *			like SPI bus configuration.
+ * @spi_padding_bytes:	Number of padding bytes that must be thrown out before
+ *			read data gets returned. This is calculated during
+ *			initialization based on bus speed.
+ * @dummy_buf:		Zero-filled buffer of spi_padding_bytes size. The dummy
+ *			bytes that will be sent out between the address and
+ *			data of a SPI read operation.
+ */
+struct ocelot_ddata {
+	struct regmap *gcb_regmap;
+	struct regmap *cpuorg_regmap;
+	int spi_padding_bytes;
+	void *dummy_buf;
+};
+
+int ocelot_chip_reset(struct device *dev);
+int ocelot_core_init(struct device *dev);
+
+/* SPI-specific routines that won't be necessary for other interfaces */
+struct regmap *ocelot_spi_init_regmap(struct device *dev,
+				      const struct resource *res);
+
+#define OCELOT_SPI_BYTE_ORDER_LE 0x00000000
+#define OCELOT_SPI_BYTE_ORDER_BE 0x81818181
+
+#ifdef __LITTLE_ENDIAN
+#define OCELOT_SPI_BYTE_ORDER OCELOT_SPI_BYTE_ORDER_LE
+#else
+#define OCELOT_SPI_BYTE_ORDER OCELOT_SPI_BYTE_ORDER_BE
+#endif
+
+#endif