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, 55 insertions, 0 deletions

diff --git a/tools/perf/python/tracepoint.py b/tools/perf/python/tracepoint.py
new file mode 100755
index 000000000..15b0c8268
--- /dev/null
+++ b/tools/perf/python/tracepoint.py
@@ -0,0 +1,55 @@
+#! /usr/bin/env python
+# SPDX-License-Identifier: GPL-2.0
+# -*- python -*-
+# -*- coding: utf-8 -*-
+
+import perf
+
+def change_proctitle():
+    try:
+        import setproctitle
+        setproctitle.setproctitle("tracepoint.py")
+    except:
+        print("Install the setproctitle python package to help with top and friends")
+
+def main():
+    change_proctitle()
+    cpus    = perf.cpu_map()
+    threads = perf.thread_map(-1)
+    evlist = perf.parse_events("sched:sched_switch", cpus, threads)
+    # Disable tracking of mmaps and similar that are unnecessary.
+    for ev in evlist:
+        ev.tracking = False
+    # Configure evsels with default record options.
+    evlist.config()
+    # Simplify the sample_type and read_format of evsels
+    for ev in evlist:
+        ev.sample_type = ev.sample_type & ~perf.SAMPLE_IP
+        ev.read_format = 0
+
+    evlist.open()
+    evlist.mmap()
+    evlist.enable();
+
+    while True:
+        evlist.poll(timeout = -1)
+        for cpu in cpus:
+            event = evlist.read_on_cpu(cpu)
+            if not event:
+                continue
+
+            if not isinstance(event, perf.sample_event):
+                continue
+
+            print("time %u prev_comm=%s prev_pid=%d prev_prio=%d prev_state=0x%x ==> next_comm=%s next_pid=%d next_prio=%d" % (
+                   event.sample_time,
+                   event.prev_comm,
+                   event.prev_pid,
+                   event.prev_prio,
+                   event.prev_state,
+                   event.next_comm,
+                   event.next_pid,
+                   event.next_prio))
+
+if __name__ == '__main__':
+    main()