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, 135 insertions, 0 deletions

diff --git a/drivers/clk/sprd/gate.c b/drivers/clk/sprd/gate.c
new file mode 100644
index 000000000..56e1714b5
--- /dev/null
+++ b/drivers/clk/sprd/gate.c
@@ -0,0 +1,135 @@
+// SPDX-License-Identifier: GPL-2.0
+//
+// Spreadtrum gate clock driver
+//
+// Copyright (C) 2017 Spreadtrum, Inc.
+// Author: Chunyan Zhang <chunyan.zhang@spreadtrum.com>
+
+#include <linux/clk-provider.h>
+#include <linux/regmap.h>
+
+#include "gate.h"
+
+static void clk_gate_toggle(const struct sprd_gate *sg, bool en)
+{
+	const struct sprd_clk_common *common = &sg->common;
+	unsigned int reg;
+	bool set = sg->flags & CLK_GATE_SET_TO_DISABLE ? true : false;
+
+	set ^= en;
+
+	regmap_read(common->regmap, common->reg, &reg);
+
+	if (set)
+		reg |= sg->enable_mask;
+	else
+		reg &= ~sg->enable_mask;
+
+	regmap_write(common->regmap, common->reg, reg);
+}
+
+static void clk_sc_gate_toggle(const struct sprd_gate *sg, bool en)
+{
+	const struct sprd_clk_common *common = &sg->common;
+	bool set = sg->flags & CLK_GATE_SET_TO_DISABLE ? 1 : 0;
+	unsigned int offset;
+
+	set ^= en;
+
+	/*
+	 * Each set/clear gate clock has three registers:
+	 * common->reg			- base register
+	 * common->reg + offset		- set register
+	 * common->reg + 2 * offset	- clear register
+	 */
+	offset = set ? sg->sc_offset : sg->sc_offset * 2;
+
+	regmap_write(common->regmap, common->reg + offset,
+			  sg->enable_mask);
+}
+
+static void sprd_gate_disable(struct clk_hw *hw)
+{
+	struct sprd_gate *sg = hw_to_sprd_gate(hw);
+
+	clk_gate_toggle(sg, false);
+}
+
+static int sprd_gate_enable(struct clk_hw *hw)
+{
+	struct sprd_gate *sg = hw_to_sprd_gate(hw);
+
+	clk_gate_toggle(sg, true);
+
+	return 0;
+}
+
+static void sprd_sc_gate_disable(struct clk_hw *hw)
+{
+	struct sprd_gate *sg = hw_to_sprd_gate(hw);
+
+	clk_sc_gate_toggle(sg, false);
+}
+
+static int sprd_sc_gate_enable(struct clk_hw *hw)
+{
+	struct sprd_gate *sg = hw_to_sprd_gate(hw);
+
+	clk_sc_gate_toggle(sg, true);
+
+	return 0;
+}
+
+static int sprd_pll_sc_gate_prepare(struct clk_hw *hw)
+{
+	struct sprd_gate *sg = hw_to_sprd_gate(hw);
+
+	clk_sc_gate_toggle(sg, true);
+	udelay(sg->udelay);
+
+	return 0;
+}
+
+static int sprd_gate_is_enabled(struct clk_hw *hw)
+{
+	struct sprd_gate *sg = hw_to_sprd_gate(hw);
+	struct sprd_clk_common *common = &sg->common;
+	struct clk_hw *parent;
+	unsigned int reg;
+
+	if (sg->flags & SPRD_GATE_NON_AON) {
+		parent = clk_hw_get_parent(hw);
+		if (!parent || !clk_hw_is_enabled(parent))
+			return 0;
+	}
+
+	regmap_read(common->regmap, common->reg, &reg);
+
+	if (sg->flags & CLK_GATE_SET_TO_DISABLE)
+		reg ^= sg->enable_mask;
+
+	reg &= sg->enable_mask;
+
+	return reg ? 1 : 0;
+}
+
+const struct clk_ops sprd_gate_ops = {
+	.disable	= sprd_gate_disable,
+	.enable		= sprd_gate_enable,
+	.is_enabled	= sprd_gate_is_enabled,
+};
+EXPORT_SYMBOL_GPL(sprd_gate_ops);
+
+const struct clk_ops sprd_sc_gate_ops = {
+	.disable	= sprd_sc_gate_disable,
+	.enable		= sprd_sc_gate_enable,
+	.is_enabled	= sprd_gate_is_enabled,
+};
+EXPORT_SYMBOL_GPL(sprd_sc_gate_ops);
+
+const struct clk_ops sprd_pll_sc_gate_ops = {
+	.unprepare	= sprd_sc_gate_disable,
+	.prepare	= sprd_pll_sc_gate_prepare,
+	.is_enabled	= sprd_gate_is_enabled,
+};
+EXPORT_SYMBOL_GPL(sprd_pll_sc_gate_ops);