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, 39 insertions, 0 deletions

diff --git a/include/net/dcbevent.h b/include/net/dcbevent.h
new file mode 100644
index 000000000..02700262f
--- /dev/null
+++ b/include/net/dcbevent.h
@@ -0,0 +1,39 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Copyright (c) 2010, Intel Corporation.
+ *
+ * Author: John Fastabend <john.r.fastabend@intel.com>
+ */
+
+#ifndef _DCB_EVENT_H
+#define _DCB_EVENT_H
+
+struct notifier_block;
+
+enum dcbevent_notif_type {
+	DCB_APP_EVENT = 1,
+};
+
+#ifdef CONFIG_DCB
+int register_dcbevent_notifier(struct notifier_block *nb);
+int unregister_dcbevent_notifier(struct notifier_block *nb);
+int call_dcbevent_notifiers(unsigned long val, void *v);
+#else
+static inline int
+register_dcbevent_notifier(struct notifier_block *nb)
+{
+	return 0;
+}
+
+static inline int unregister_dcbevent_notifier(struct notifier_block *nb)
+{
+	return 0;
+}
+
+static inline int call_dcbevent_notifiers(unsigned long val, void *v)
+{
+	return 0;
+}
+#endif /* CONFIG_DCB */
+
+#endif