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, 35 insertions, 0 deletions

diff --git a/include/misc/altera.h b/include/misc/altera.h
new file mode 100644
index 000000000..60cb5c598
--- /dev/null
+++ b/include/misc/altera.h
@@ -0,0 +1,35 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+/*
+ * altera.h
+ *
+ * altera FPGA driver
+ *
+ * Copyright (C) Altera Corporation 1998-2001
+ * Copyright (C) 2010 NetUP Inc.
+ * Copyright (C) 2010 Igor M. Liplianin <liplianin@netup.ru>
+ */
+
+#ifndef _ALTERA_H_
+#define _ALTERA_H_
+
+struct altera_config {
+	void *dev;
+	u8 *action;
+	int (*jtag_io) (void *dev, int tms, int tdi, int tdo);
+};
+
+#if defined(CONFIG_ALTERA_STAPL) || \
+		(defined(CONFIG_ALTERA_STAPL_MODULE) && defined(MODULE))
+
+extern int altera_init(struct altera_config *config, const struct firmware *fw);
+#else
+
+static inline int altera_init(struct altera_config *config,
+						const struct firmware *fw)
+{
+	printk(KERN_WARNING "%s: driver disabled by Kconfig\n", __func__);
+	return 0;
+}
+#endif /* CONFIG_ALTERA_STAPL */
+
+#endif /* _ALTERA_H_ */