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, 83 insertions, 0 deletions

diff --git a/include/memory/renesas-rpc-if.h b/include/memory/renesas-rpc-if.h
new file mode 100644
index 000000000..53663c4e5
--- /dev/null
+++ b/include/memory/renesas-rpc-if.h
@@ -0,0 +1,83 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Renesas RPC-IF core driver
+ *
+ * Copyright (C) 2018~2019 Renesas Solutions Corp.
+ * Copyright (C) 2019 Macronix International Co., Ltd.
+ * Copyright (C) 2019-2020 Cogent Embedded, Inc.
+ */
+
+#ifndef __RENESAS_RPC_IF_H
+#define __RENESAS_RPC_IF_H
+
+#include <linux/pm_runtime.h>
+#include <linux/types.h>
+
+enum rpcif_data_dir {
+	RPCIF_NO_DATA,
+	RPCIF_DATA_IN,
+	RPCIF_DATA_OUT,
+};
+
+struct rpcif_op {
+	struct {
+		u8 buswidth;
+		u8 opcode;
+		bool ddr;
+	} cmd, ocmd;
+
+	struct {
+		u8 nbytes;
+		u8 buswidth;
+		bool ddr;
+		u64 val;
+	} addr;
+
+	struct {
+		u8 ncycles;
+		u8 buswidth;
+	} dummy;
+
+	struct {
+		u8 nbytes;
+		u8 buswidth;
+		bool ddr;
+		u32 val;
+	} option;
+
+	struct {
+		u8 buswidth;
+		unsigned int nbytes;
+		enum rpcif_data_dir dir;
+		bool ddr;
+		union {
+			void *in;
+			const void *out;
+		} buf;
+	} data;
+};
+
+enum rpcif_type {
+	RPCIF_RCAR_GEN3,
+	RPCIF_RCAR_GEN4,
+	RPCIF_RZ_G2L,
+	XSPI_RZ_G3E,
+};
+
+struct rpcif {
+	struct device *dev;
+	void __iomem *dirmap;
+	size_t size;
+	bool xspi;
+};
+
+int rpcif_sw_init(struct rpcif *rpc, struct device *dev);
+int rpcif_hw_init(struct device *dev, bool hyperflash);
+void rpcif_prepare(struct device *dev, const struct rpcif_op *op, u64 *offs,
+		   size_t *len);
+int rpcif_manual_xfer(struct device *dev);
+ssize_t rpcif_dirmap_read(struct device *dev, u64 offs, size_t len, void *buf);
+ssize_t xspi_dirmap_write(struct device *dev, u64 offs, size_t len,
+			  const void *buf);
+
+#endif // __RENESAS_RPC_IF_H