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, 71 insertions, 0 deletions

diff --git a/tools/perf/util/counts.c b/tools/perf/util/counts.c
new file mode 100644
index 000000000..11cd85b27
--- /dev/null
+++ b/tools/perf/util/counts.c
@@ -0,0 +1,71 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <errno.h>
+#include <stdlib.h>
+#include <string.h>
+#include "evsel.h"
+#include "counts.h"
+#include <perf/threadmap.h>
+#include <linux/zalloc.h>
+
+struct perf_counts *perf_counts__new(int ncpus, int nthreads)
+{
+	struct perf_counts *counts = zalloc(sizeof(*counts));
+
+	if (counts) {
+		struct xyarray *values;
+
+		values = xyarray__new(ncpus, nthreads, sizeof(struct perf_counts_values));
+		if (!values) {
+			free(counts);
+			return NULL;
+		}
+
+		counts->values = values;
+
+		values = xyarray__new(ncpus, nthreads, sizeof(bool));
+		if (!values) {
+			xyarray__delete(counts->values);
+			free(counts);
+			return NULL;
+		}
+
+		counts->loaded = values;
+	}
+
+	return counts;
+}
+
+void perf_counts__delete(struct perf_counts *counts)
+{
+	if (counts) {
+		xyarray__delete(counts->loaded);
+		xyarray__delete(counts->values);
+		free(counts);
+	}
+}
+
+void perf_counts__reset(struct perf_counts *counts)
+{
+	xyarray__reset(counts->loaded);
+	xyarray__reset(counts->values);
+}
+
+void evsel__reset_counts(struct evsel *evsel)
+{
+	perf_counts__reset(evsel->counts);
+}
+
+int evsel__alloc_counts(struct evsel *evsel)
+{
+	struct perf_cpu_map *cpus = evsel__cpus(evsel);
+	int nthreads = perf_thread_map__nr(evsel->core.threads);
+
+	evsel->counts = perf_counts__new(perf_cpu_map__nr(cpus), nthreads);
+	return evsel->counts != NULL ? 0 : -ENOMEM;
+}
+
+void evsel__free_counts(struct evsel *evsel)
+{
+	perf_counts__delete(evsel->counts);
+	evsel->counts = NULL;
+}