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, 54 insertions, 0 deletions

diff --git a/drivers/clk/versatile/icst.h b/drivers/clk/versatile/icst.h
new file mode 100644
index 000000000..29622768b
--- /dev/null
+++ b/drivers/clk/versatile/icst.h
@@ -0,0 +1,54 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ *  Copyright (C) 2003 Deep Blue Solutions, Ltd, All Rights Reserved.
+ *
+ *  Support functions for calculating clocks/divisors for the ICST
+ *  clock generators.  See https://www.idt.com/ for more information
+ *  on these devices.
+ */
+#ifndef ICST_H
+#define ICST_H
+
+struct icst_params {
+	unsigned long	ref;
+	unsigned long	vco_max;	/* inclusive */
+	unsigned long	vco_min;	/* exclusive */
+	unsigned short	vd_min;		/* inclusive */
+	unsigned short	vd_max;		/* inclusive */
+	unsigned char	rd_min;		/* inclusive */
+	unsigned char	rd_max;		/* inclusive */
+	const unsigned char *s2div;	/* chip specific s2div array */
+	const unsigned char *idx2s;	/* chip specific idx2s array */
+};
+
+struct icst_vco {
+	unsigned short	v;
+	unsigned char	r;
+	unsigned char	s;
+};
+
+unsigned long icst_hz(const struct icst_params *p, struct icst_vco vco);
+struct icst_vco icst_hz_to_vco(const struct icst_params *p, unsigned long freq);
+
+/*
+ * ICST307 VCO frequency must be between 6MHz and 200MHz (3.3 or 5V).
+ * This frequency is pre-output divider.
+ */
+#define ICST307_VCO_MIN	6000000
+#define ICST307_VCO_MAX	200000000
+
+extern const unsigned char icst307_s2div[];
+extern const unsigned char icst307_idx2s[];
+
+/*
+ * ICST525 VCO frequency must be between 10MHz and 200MHz (3V) or 320MHz (5V).
+ * This frequency is pre-output divider.
+ */
+#define ICST525_VCO_MIN		10000000
+#define ICST525_VCO_MAX_3V	200000000
+#define ICST525_VCO_MAX_5V	320000000
+
+extern const unsigned char icst525_s2div[];
+extern const unsigned char icst525_idx2s[];
+
+#endif