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, 187 insertions, 0 deletions

diff --git a/tools/perf/bench/pmu-scan.c b/tools/perf/bench/pmu-scan.c
new file mode 100644
index 000000000..14a464ad8
--- /dev/null
+++ b/tools/perf/bench/pmu-scan.c
@@ -0,0 +1,187 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Benchmark scanning sysfs files for PMU information.
+ *
+ * Copyright 2023 Google LLC.
+ */
+#include <errno.h>
+#include <stdio.h>
+#include "bench.h"
+#include "util/debug.h"
+#include "util/pmu.h"
+#include "util/pmus.h"
+#include "util/stat.h"
+#include <linux/atomic.h>
+#include <linux/err.h>
+#include <linux/time64.h>
+#include <subcmd/parse-options.h>
+
+static unsigned int iterations = 100;
+
+struct pmu_scan_result {
+	char *name;
+	int nr_aliases;
+	int nr_formats;
+	int nr_caps;
+	bool is_core;
+};
+
+static const struct option options[] = {
+	OPT_UINTEGER('i', "iterations", &iterations,
+		"Number of iterations used to compute average"),
+	OPT_END()
+};
+
+static const char *const bench_usage[] = {
+	"perf bench internals pmu-scan <options>",
+	NULL
+};
+
+static int nr_pmus;
+static struct pmu_scan_result *results;
+
+static int save_result(void)
+{
+	struct perf_pmu *pmu = NULL;
+	struct list_head *list;
+	struct pmu_scan_result *r;
+
+	while ((pmu = perf_pmus__scan(pmu)) != NULL) {
+		r = realloc(results, (nr_pmus + 1) * sizeof(*r));
+		if (r == NULL)
+			return -ENOMEM;
+
+		results = r;
+		r = results + nr_pmus;
+
+		r->name = strdup(pmu->name);
+		r->is_core = pmu->is_core;
+		r->nr_caps = pmu->nr_caps;
+
+		r->nr_aliases = perf_pmu__num_events(pmu);
+
+		r->nr_formats = 0;
+		list_for_each(list, &pmu->format)
+			r->nr_formats++;
+
+		pr_debug("pmu[%d] name=%s, nr_caps=%d, nr_aliases=%d, nr_formats=%d\n",
+			nr_pmus, r->name, r->nr_caps, r->nr_aliases, r->nr_formats);
+		nr_pmus++;
+	}
+
+	perf_pmus__destroy();
+	return 0;
+}
+
+static int check_result(bool core_only)
+{
+	struct pmu_scan_result *r;
+	struct perf_pmu *pmu;
+	struct list_head *list;
+	int nr;
+
+	for (int i = 0; i < nr_pmus; i++) {
+		r = &results[i];
+		if (core_only && !r->is_core)
+			continue;
+
+		pmu = perf_pmus__find(r->name);
+		if (pmu == NULL) {
+			pr_err("Cannot find PMU %s\n", r->name);
+			return -1;
+		}
+
+		if (pmu->nr_caps != (u32)r->nr_caps) {
+			pr_err("Unmatched number of event caps in %s: expect %d vs got %d\n",
+				pmu->name, r->nr_caps, pmu->nr_caps);
+			return -1;
+		}
+
+		nr = perf_pmu__num_events(pmu);
+		if (nr != r->nr_aliases) {
+			pr_err("Unmatched number of event aliases in %s: expect %d vs got %d\n",
+				pmu->name, r->nr_aliases, nr);
+			return -1;
+		}
+
+		nr = 0;
+		list_for_each(list, &pmu->format)
+			nr++;
+		if (nr != r->nr_formats) {
+			pr_err("Unmatched number of event formats in %s: expect %d vs got %d\n",
+				pmu->name, r->nr_formats, nr);
+			return -1;
+		}
+	}
+	return 0;
+}
+
+static void delete_result(void)
+{
+	for (int i = 0; i < nr_pmus; i++)
+		free(results[i].name);
+	free(results);
+
+	results = NULL;
+	nr_pmus = 0;
+}
+
+static int run_pmu_scan(void)
+{
+	struct stats stats;
+	struct timeval start, end, diff;
+	double time_average, time_stddev;
+	u64 runtime_us;
+	int ret;
+
+	init_stats(&stats);
+	pr_info("Computing performance of sysfs PMU event scan for %u times\n",
+		iterations);
+
+	if (save_result() < 0) {
+		pr_err("Failed to initialize PMU scan result\n");
+		return -1;
+	}
+
+	for (int j = 0; j < 2; j++) {
+		bool core_only = (j == 0);
+
+		for (unsigned int i = 0; i < iterations; i++) {
+			gettimeofday(&start, NULL);
+			if (core_only)
+				perf_pmus__scan_core(NULL);
+			else
+				perf_pmus__scan(NULL);
+			gettimeofday(&end, NULL);
+			timersub(&end, &start, &diff);
+			runtime_us = diff.tv_sec * USEC_PER_SEC + diff.tv_usec;
+			update_stats(&stats, runtime_us);
+
+			ret = check_result(core_only);
+			perf_pmus__destroy();
+			if (ret < 0)
+				break;
+		}
+		time_average = avg_stats(&stats);
+		time_stddev = stddev_stats(&stats);
+		pr_info("  Average%s PMU scanning took: %.3f usec (+- %.3f usec)\n",
+			core_only ? " core" : "", time_average, time_stddev);
+	}
+	delete_result();
+	return 0;
+}
+
+int bench_pmu_scan(int argc, const char **argv)
+{
+	int err = 0;
+
+	argc = parse_options(argc, argv, options, bench_usage, 0);
+	if (argc) {
+		usage_with_options(bench_usage, options);
+		exit(EXIT_FAILURE);
+	}
+
+	err = run_pmu_scan();
+
+	return err;
+}