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, 38 insertions, 0 deletions

diff --git a/scripts/package/gen-diff-patch b/scripts/package/gen-diff-patch
new file mode 100755
index 000000000..f272f7770
--- /dev/null
+++ b/scripts/package/gen-diff-patch
@@ -0,0 +1,38 @@
+#!/bin/sh
+# SPDX-License-Identifier: GPL-2.0-only
+
+set -eu
+
+diff_patch=$1
+
+mkdir -p "$(dirname "${diff_patch}")"
+
+git -C "${srctree:-.}" diff HEAD > "${diff_patch}"
+
+if [ ! -s "${diff_patch}" ] ||
+   [ -z "$(git -C "${srctree:-.}" ls-files --other --exclude-standard | head -n1)" ]; then
+	exit
+fi
+
+# The source tarball, which is generated by 'git archive', contains everything
+# you committed in the repository. If you have local diff ('git diff HEAD'),
+# it will go into ${diff_patch}. If untracked files are remaining, the resulting
+# source package may not be correct.
+#
+# Examples:
+#  - You modified a source file to add #include "new-header.h"
+#    but forgot to add new-header.h
+#  - You modified a Makefile to add 'obj-$(CONFIG_FOO) += new-dirver.o'
+#    but you forgot to add new-driver.c
+#
+# You need to commit them, or at least stage them by 'git add'.
+#
+# This script does not take care of untracked files because doing so would
+# introduce additional complexity. Instead, print a warning message here if
+# untracked files are found.
+# If all untracked files are just garbage, you can ignore this warning.
+echo >&2 "============================ WARNING ============================"
+echo >&2 "Your working tree has diff from HEAD, and also untracked file(s)."
+echo >&2 "Please make sure you did 'git add' for all new files you need in"
+echo >&2 "the source package."
+echo >&2 "================================================================="