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, 36 insertions, 0 deletions

diff --git a/drivers/ipack/devices/ipoctal.h b/drivers/ipack/devices/ipoctal.h
new file mode 100644
index 000000000..773dc41bd
--- /dev/null
+++ b/drivers/ipack/devices/ipoctal.h
@@ -0,0 +1,36 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * driver for the IPOCTAL boards
+ *
+ * Copyright (C) 2009-2012 CERN (www.cern.ch)
+ * Author: Nicolas Serafini, EIC2 SA
+ * Author: Samuel Iglesias Gonsalvez <siglesias@igalia.com>
+ */
+
+#ifndef _IPOCTAL_H_
+#define _IPOCTAL_H_
+
+#define NR_CHANNELS		8
+#define IPOCTAL_MAX_BOARDS	16
+#define MAX_DEVICES		(NR_CHANNELS * IPOCTAL_MAX_BOARDS)
+
+/**
+ * struct ipoctal_stats -- Stats since last reset
+ *
+ * @tx: Number of transmitted bytes
+ * @rx: Number of received bytes
+ * @overrun: Number of overrun errors
+ * @parity_err: Number of parity errors
+ * @framing_err: Number of framing errors
+ * @rcv_break: Number of break received
+ */
+struct ipoctal_stats {
+	unsigned long tx;
+	unsigned long rx;
+	unsigned long overrun_err;
+	unsigned long parity_err;
+	unsigned long framing_err;
+	unsigned long rcv_break;
+};
+
+#endif /* _IPOCTAL_H_ */