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, 45 insertions, 0 deletions

diff --git a/tools/perf/util/counts.h b/tools/perf/util/counts.h
new file mode 100644
index 000000000..42760242e
--- /dev/null
+++ b/tools/perf/util/counts.h
@@ -0,0 +1,45 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef __PERF_COUNTS_H
+#define __PERF_COUNTS_H
+
+#include <linux/types.h>
+#include <internal/xyarray.h>
+#include <perf/evsel.h>
+#include <stdbool.h>
+
+struct evsel;
+
+struct perf_counts {
+	s8			  scaled;
+	struct xyarray		  *values;
+	struct xyarray		  *loaded;
+};
+
+
+static inline struct perf_counts_values*
+perf_counts(struct perf_counts *counts, int cpu_map_idx, int thread)
+{
+	return xyarray__entry(counts->values, cpu_map_idx, thread);
+}
+
+static inline bool
+perf_counts__is_loaded(struct perf_counts *counts, int cpu_map_idx, int thread)
+{
+	return *((bool *) xyarray__entry(counts->loaded, cpu_map_idx, thread));
+}
+
+static inline void
+perf_counts__set_loaded(struct perf_counts *counts, int cpu_map_idx, int thread, bool loaded)
+{
+	*((bool *) xyarray__entry(counts->loaded, cpu_map_idx, thread)) = loaded;
+}
+
+struct perf_counts *perf_counts__new(int ncpus, int nthreads);
+void perf_counts__delete(struct perf_counts *counts);
+void perf_counts__reset(struct perf_counts *counts);
+
+void evsel__reset_counts(struct evsel *evsel);
+int evsel__alloc_counts(struct evsel *evsel);
+void evsel__free_counts(struct evsel *evsel);
+
+#endif /* __PERF_COUNTS_H */