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, 33 insertions, 0 deletions

diff --git a/lib/kunit/hooks-impl.h b/lib/kunit/hooks-impl.h
new file mode 100644
index 000000000..d8720f261
--- /dev/null
+++ b/lib/kunit/hooks-impl.h
@@ -0,0 +1,33 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Declarations for hook implementations.
+ *
+ * These will be set as the function pointers in struct kunit_hook_table,
+ * found in include/kunit/test-bug.h.
+ *
+ * Copyright (C) 2023, Google LLC.
+ * Author: David Gow <davidgow@google.com>
+ */
+
+#ifndef _KUNIT_HOOKS_IMPL_H
+#define _KUNIT_HOOKS_IMPL_H
+
+#include <kunit/test-bug.h>
+
+/* List of declarations. */
+void __printf(3, 4) __kunit_fail_current_test_impl(const char *file,
+						   int line,
+						   const char *fmt, ...);
+void *__kunit_get_static_stub_address_impl(struct kunit *test, void *real_fn_addr);
+bool __kunit_is_suppressed_warning_impl(bool count);
+
+/* Code to set all of the function pointers. */
+static inline void kunit_install_hooks(void)
+{
+	/* Install the KUnit hook functions. */
+	kunit_hooks.fail_current_test = __kunit_fail_current_test_impl;
+	kunit_hooks.get_static_stub_address = __kunit_get_static_stub_address_impl;
+	kunit_hooks.is_suppressed_warning = __kunit_is_suppressed_warning_impl;
+}
+
+#endif /* _KUNIT_HOOKS_IMPL_H */