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>

3 files changed, 96 insertions, 0 deletions

diff --git a/tools/testing/selftests/module/Makefile b/tools/testing/selftests/module/Makefile
new file mode 100644
index 000000000..6132d7ddb
--- /dev/null
+++ b/tools/testing/selftests/module/Makefile
@@ -0,0 +1,12 @@
+# SPDX-License-Identifier: GPL-2.0-only
+# Makefile for module loading selftests
+
+# No binaries, but make sure arg-less "make" doesn't trigger "run_tests"
+all:
+
+TEST_PROGS := find_symbol.sh
+
+include ../lib.mk
+
+# Nothing to clean up.
+clean:
diff --git a/tools/testing/selftests/module/config b/tools/testing/selftests/module/config
new file mode 100644
index 000000000..b0c206b1a
--- /dev/null
+++ b/tools/testing/selftests/module/config
@@ -0,0 +1,3 @@
+CONFIG_TEST_RUNTIME=y
+CONFIG_TEST_RUNTIME_MODULE=y
+CONFIG_TEST_KALLSYMS=m
diff --git a/tools/testing/selftests/module/find_symbol.sh b/tools/testing/selftests/module/find_symbol.sh
new file mode 100755
index 000000000..2c56805c9
--- /dev/null
+++ b/tools/testing/selftests/module/find_symbol.sh
@@ -0,0 +1,81 @@
+#!/bin/bash
+# SPDX-License-Identifier: GPL-2.0-or-later OR copyleft-next-0.3.1
+# Copyright (C) 2023 Luis Chamberlain <mcgrof@kernel.org>
+#
+# This is a stress test script for kallsyms through find_symbol()
+
+set -e
+
+# Kselftest framework requirement - SKIP code is 4.
+ksft_skip=4
+
+test_reqs()
+{
+	if ! which modprobe 2> /dev/null > /dev/null; then
+		echo "$0: You need modprobe installed" >&2
+		exit $ksft_skip
+	fi
+
+	if ! which kmod 2> /dev/null > /dev/null; then
+		echo "$0: You need kmod installed" >&2
+		exit $ksft_skip
+	fi
+
+	if ! which perf 2> /dev/null > /dev/null; then
+		echo "$0: You need perf installed" >&2
+		exit $ksft_skip
+	fi
+
+	uid=$(id -u)
+	if [ $uid -ne 0 ]; then
+		echo $msg must be run as root >&2
+		exit $ksft_skip
+	fi
+}
+
+load_mod()
+{
+	local STATS="-e duration_time"
+	STATS="$STATS -e user_time"
+	STATS="$STATS -e system_time"
+	STATS="$STATS -e page-faults"
+	local MOD=$1
+
+	local ARCH="$(uname -m)"
+	case "${ARCH}" in
+	x86_64)
+		perf stat $STATS $MODPROBE $MOD
+		;;
+	*)
+		time $MODPROBE $MOD
+		exit 1
+		;;
+	esac
+}
+
+remove_all()
+{
+	$MODPROBE -r test_kallsyms_b
+	for i in a b c d; do
+		$MODPROBE -r test_kallsyms_$i
+	done
+}
+test_reqs
+
+MODPROBE=$(</proc/sys/kernel/modprobe)
+
+remove_all
+load_mod test_kallsyms_b
+remove_all
+
+# Now pollute the namespace
+$MODPROBE test_kallsyms_c
+load_mod test_kallsyms_b
+
+# Now pollute the namespace with twice the number of symbols than the last time
+remove_all
+$MODPROBE test_kallsyms_c
+$MODPROBE test_kallsyms_d
+load_mod test_kallsyms_b
+
+exit 0