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, 26 insertions, 0 deletions

diff --git a/drivers/firewire/nosy-user.h b/drivers/firewire/nosy-user.h
new file mode 100644
index 000000000..3446c5b77
--- /dev/null
+++ b/drivers/firewire/nosy-user.h
@@ -0,0 +1,26 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef __nosy_user_h
+#define __nosy_user_h
+
+#include <linux/ioctl.h>
+#include <linux/types.h>
+
+#define NOSY_IOC_GET_STATS _IOR('&', 0, struct nosy_stats)
+#define NOSY_IOC_START     _IO('&', 1)
+#define NOSY_IOC_STOP      _IO('&', 2)
+#define NOSY_IOC_FILTER    _IOW('&', 2, __u32)
+
+struct nosy_stats {
+	__u32 total_packet_count;
+	__u32 lost_packet_count;
+};
+
+/*
+ * Format of packets returned from the kernel driver:
+ *
+ *	quadlet with timestamp		(microseconds, CPU endian)
+ *	quadlet-padded packet data...	(little endian)
+ *	quadlet with ack		(little endian)
+ */
+
+#endif /* __nosy_user_h */