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/scripts/Lindent b/scripts/Lindent
new file mode 100755
index 000000000..1688c44c2
--- /dev/null
+++ b/scripts/Lindent
@@ -0,0 +1,26 @@
+#!/bin/sh
+# SPDX-License-Identifier: GPL-2.0
+
+PARAM="-npro -kr -i8 -ts8 -sob -l80 -ss -ncs -cp1"
+
+RES=`indent --version | cut -d' ' -f3`
+if [ "$RES" = "" ]; then
+	exit 1
+fi
+V1=`echo $RES | cut -d'.' -f1`
+V2=`echo $RES | cut -d'.' -f2`
+V3=`echo $RES | cut -d'.' -f3`
+
+if [ $V1 -gt 2 ]; then
+  PARAM="$PARAM -il0"
+elif [ $V1 -eq 2 ]; then
+  if [ $V2 -gt 2 ]; then
+    PARAM="$PARAM -il0"
+  elif [ $V2 -eq 2 ]; then
+    if [ $V3 -ge 10 ]; then
+      PARAM="$PARAM -il0"
+    fi
+  fi
+fi
+
+indent $PARAM "$@"