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, 38 insertions, 0 deletions

diff --git a/drivers/clk/clk.h b/drivers/clk/clk.h
new file mode 100644
index 000000000..2d801900c
--- /dev/null
+++ b/drivers/clk/clk.h
@@ -0,0 +1,38 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Copyright (C) 2013 Samsung Electronics Co., Ltd.
+ * Sylwester Nawrocki <s.nawrocki@samsung.com>
+ */
+
+struct clk_hw;
+struct device;
+struct of_phandle_args;
+
+#if defined(CONFIG_OF) && defined(CONFIG_COMMON_CLK)
+struct clk_hw *of_clk_get_hw(struct device_node *np,
+				    int index, const char *con_id);
+#else /* !CONFIG_COMMON_CLK || !CONFIG_OF */
+static inline struct clk_hw *of_clk_get_hw(struct device_node *np,
+				    int index, const char *con_id)
+{
+	return ERR_PTR(-ENOENT);
+}
+#endif
+
+struct clk_hw *clk_find_hw(const char *dev_id, const char *con_id);
+
+#ifdef CONFIG_COMMON_CLK
+struct clk *clk_hw_create_clk(struct device *dev, struct clk_hw *hw,
+			      const char *dev_id, const char *con_id);
+void __clk_put(struct clk *clk);
+#else
+/* All these casts to avoid ifdefs in clkdev... */
+static inline struct clk *
+clk_hw_create_clk(struct device *dev, struct clk_hw *hw, const char *dev_id,
+		  const char *con_id)
+{
+	return (struct clk *)hw;
+}
+static inline void __clk_put(struct clk *clk) { }
+
+#endif