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, 19 insertions, 0 deletions

diff --git a/Documentation/sphinx/templates/kernel-toc.html b/Documentation/sphinx/templates/kernel-toc.html
new file mode 100644
index 000000000..b84969bd3
--- /dev/null
+++ b/Documentation/sphinx/templates/kernel-toc.html
@@ -0,0 +1,19 @@
+{# SPDX-License-Identifier: GPL-2.0 #}
+
+{# Create a local TOC the kernel way #}
+<p>
+<h3 class="kernel-toc-contents">Contents</h3>
+<input type="checkbox" class="kernel-toc-toggle" id = "kernel-toc-toggle" checked>
+<label class="kernel-toc-title" for="kernel-toc-toggle"></label>
+
+<div class="kerneltoc" id="kerneltoc">
+{{ toctree(maxdepth=3) }}
+</div>
+{# hacky script to try to position the left column #}
+<script type="text/javascript"> <!--
+  var sbar = document.getElementsByClassName("sphinxsidebar")[0];
+  let currents = document.getElementsByClassName("current")
+  if (currents.length) {
+    sbar.scrollTop = currents[currents.length - 1].offsetTop;
+  }
+  --> </script>