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, 76 insertions, 0 deletions

diff --git a/tools/perf/util/units.c b/tools/perf/util/units.c
new file mode 100644
index 000000000..0bbacf5a2
--- /dev/null
+++ b/tools/perf/util/units.c
@@ -0,0 +1,76 @@
+// SPDX-License-Identifier: GPL-2.0
+#include "units.h"
+#include <inttypes.h>
+#include <limits.h>
+#include <stdlib.h>
+#include <string.h>
+#include <linux/kernel.h>
+#include <linux/time64.h>
+
+unsigned long parse_tag_value(const char *str, struct parse_tag *tags)
+{
+	struct parse_tag *i = tags;
+
+	while (i->tag) {
+		const char *s = strchr(str, i->tag);
+
+		if (s) {
+			unsigned long int value;
+			char *endptr;
+
+			value = strtoul(str, &endptr, 10);
+			if (s != endptr)
+				break;
+
+			if (value > ULONG_MAX / i->mult)
+				break;
+			value *= i->mult;
+			return value;
+		}
+		i++;
+	}
+
+	return (unsigned long) -1;
+}
+
+double convert_unit_double(double value, char *unit)
+{
+	*unit = ' ';
+
+	if (value > 1000.0) {
+		value /= 1000.0;
+		*unit = 'K';
+	}
+
+	if (value > 1000.0) {
+		value /= 1000.0;
+		*unit = 'M';
+	}
+
+	if (value > 1000.0) {
+		value /= 1000.0;
+		*unit = 'G';
+	}
+
+	return value;
+}
+
+unsigned long convert_unit(unsigned long value, char *unit)
+{
+	double v = convert_unit_double((double)value, unit);
+
+	return (unsigned long)v;
+}
+
+int unit_number__scnprintf(char *buf, size_t size, u64 n)
+{
+	char unit[] = "BKMG";
+	int i = 0;
+
+	while (((n / 1024) > 1) && (i < 3)) {
+		n /= 1024;
+		i++;
+	}
+
+	return scnprintf(buf, size, "%" PRIu64 "%c", n, unit[i]);
+}