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, 59 insertions, 0 deletions

diff --git a/drivers/clk/sprd/composite.c b/drivers/clk/sprd/composite.c
new file mode 100644
index 000000000..ad6b6383e
--- /dev/null
+++ b/drivers/clk/sprd/composite.c
@@ -0,0 +1,59 @@
+// SPDX-License-Identifier: GPL-2.0
+//
+// Spreadtrum composite clock driver
+//
+// Copyright (C) 2017 Spreadtrum, Inc.
+// Author: Chunyan Zhang <chunyan.zhang@spreadtrum.com>
+
+#include <linux/clk-provider.h>
+
+#include "composite.h"
+
+static int sprd_comp_determine_rate(struct clk_hw *hw,
+				    struct clk_rate_request *req)
+{
+	struct sprd_comp *cc = hw_to_sprd_comp(hw);
+
+	return divider_determine_rate(hw, req, NULL, cc->div.width, 0);
+}
+
+static unsigned long sprd_comp_recalc_rate(struct clk_hw *hw,
+					  unsigned long parent_rate)
+{
+	struct sprd_comp *cc = hw_to_sprd_comp(hw);
+
+	return sprd_div_helper_recalc_rate(&cc->common, &cc->div, parent_rate);
+}
+
+static int sprd_comp_set_rate(struct clk_hw *hw, unsigned long rate,
+			     unsigned long parent_rate)
+{
+	struct sprd_comp *cc = hw_to_sprd_comp(hw);
+
+	return sprd_div_helper_set_rate(&cc->common, &cc->div,
+				       rate, parent_rate);
+}
+
+static u8 sprd_comp_get_parent(struct clk_hw *hw)
+{
+	struct sprd_comp *cc = hw_to_sprd_comp(hw);
+
+	return sprd_mux_helper_get_parent(&cc->common, &cc->mux);
+}
+
+static int sprd_comp_set_parent(struct clk_hw *hw, u8 index)
+{
+	struct sprd_comp *cc = hw_to_sprd_comp(hw);
+
+	return sprd_mux_helper_set_parent(&cc->common, &cc->mux, index);
+}
+
+const struct clk_ops sprd_comp_ops = {
+	.get_parent	= sprd_comp_get_parent,
+	.set_parent	= sprd_comp_set_parent,
+
+	.determine_rate	= sprd_comp_determine_rate,
+	.recalc_rate	= sprd_comp_recalc_rate,
+	.set_rate	= sprd_comp_set_rate,
+};
+EXPORT_SYMBOL_GPL(sprd_comp_ops);