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, 85 insertions, 0 deletions

diff --git a/tools/perf/util/unwind.h b/tools/perf/util/unwind.h
new file mode 100644
index 000000000..a2d4af694
--- /dev/null
+++ b/tools/perf/util/unwind.h
@@ -0,0 +1,85 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef __UNWIND_H
+#define __UNWIND_H
+
+#include <stdint.h>
+#include <linux/compiler.h>
+#include <linux/types.h>
+#include "map_symbol.h"
+
+struct maps;
+struct option;
+struct perf_sample;
+struct thread;
+
+struct unwind_entry {
+	struct map_symbol ms;
+	u64		  ip;
+};
+
+typedef int (*unwind_entry_cb_t)(struct unwind_entry *entry, void *arg);
+
+int unwind__configure(const char *var, const char *value, void *cb);
+int unwind__option(const struct option *opt, const char *arg, int unset);
+
+/*
+ * When best_effort is set, don't report errors and fail silently. This could
+ * be expanded in the future to be more permissive about things other than
+ * error messages.
+ */
+int unwind__get_entries(unwind_entry_cb_t cb, void *arg,
+			struct thread *thread,
+			struct perf_sample *data, int max_stack,
+			bool best_effort);
+
+#ifdef HAVE_LIBDW_SUPPORT
+int libdw__get_entries(unwind_entry_cb_t cb, void *arg,
+		       struct thread *thread,
+		       struct perf_sample *data, int max_stack,
+		       bool best_effort);
+#else
+#include "debug.h"
+static inline int libdw__get_entries(unwind_entry_cb_t cb __maybe_unused, void *arg __maybe_unused,
+				     struct thread *thread __maybe_unused,
+				     struct perf_sample *data __maybe_unused,
+				     int max_stack __maybe_unused,
+				     bool best_effort __maybe_unused)
+{
+	pr_warning_once("Error: libdw dwarf unwinding not built into perf\n");
+	return 0;
+}
+#endif
+
+#ifdef HAVE_LIBUNWIND_SUPPORT
+/* libunwind specific */
+int libunwind__get_entries(unwind_entry_cb_t cb, void *arg,
+			   struct thread *thread,
+			   struct perf_sample *data, int max_stack,
+			   bool best_effort);
+int unwind__prepare_access(struct maps *maps, uint16_t e_machine);
+void unwind__flush_access(struct maps *maps);
+void unwind__finish_access(struct maps *maps);
+#else
+#include "debug.h"
+static inline int libunwind__get_entries(unwind_entry_cb_t cb __maybe_unused,
+					 void *arg __maybe_unused,
+					 struct thread *thread __maybe_unused,
+					 struct perf_sample *data __maybe_unused,
+					 int max_stack __maybe_unused,
+					 bool best_effort __maybe_unused)
+{
+	pr_warning_once("Error: libunwind dwarf unwinding not built into perf\n");
+	return 0;
+}
+
+static inline int unwind__prepare_access(struct maps *maps __maybe_unused,
+					 uint16_t e_machine __maybe_unused)
+{
+	return 0;
+}
+
+static inline void unwind__flush_access(struct maps *maps __maybe_unused) {}
+static inline void unwind__finish_access(struct maps *maps __maybe_unused) {}
+#endif
+
+#endif /* __UNWIND_H */