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, 23 insertions, 0 deletions

diff --git a/include/net/ethoc.h b/include/net/ethoc.h
new file mode 100644
index 000000000..73810f3ca
--- /dev/null
+++ b/include/net/ethoc.h
@@ -0,0 +1,23 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * linux/include/net/ethoc.h
+ *
+ * Copyright (C) 2008-2009 Avionic Design GmbH
+ *
+ * Written by Thierry Reding <thierry.reding@avionic-design.de>
+ */
+
+#ifndef LINUX_NET_ETHOC_H
+#define LINUX_NET_ETHOC_H 1
+
+#include <linux/if.h>
+#include <linux/types.h>
+
+struct ethoc_platform_data {
+	u8 hwaddr[IFHWADDRLEN];
+	s8 phy_id;
+	u32 eth_clkfreq;
+	bool big_endian;
+};
+
+#endif /* !LINUX_NET_ETHOC_H */