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>

2 files changed, 236 insertions, 0 deletions

diff --git a/tools/testing/selftests/cpu-hotplug/Makefile b/tools/testing/selftests/cpu-hotplug/Makefile
new file mode 100644
index 000000000..8b66c4738
--- /dev/null
+++ b/tools/testing/selftests/cpu-hotplug/Makefile
@@ -0,0 +1,11 @@
+# SPDX-License-Identifier: GPL-2.0
+all:
+
+TEST_PROGS := cpu-on-off-test.sh
+
+include ../lib.mk
+
+run_full_test:
+	@/bin/bash ./cpu-on-off-test.sh -a && echo "cpu-hotplug selftests: [PASS]" || echo "cpu-hotplug selftests: [FAIL]"
+
+clean:
diff --git a/tools/testing/selftests/cpu-hotplug/cpu-on-off-test.sh b/tools/testing/selftests/cpu-hotplug/cpu-on-off-test.sh
new file mode 100755
index 000000000..287cfd580
--- /dev/null
+++ b/tools/testing/selftests/cpu-hotplug/cpu-on-off-test.sh
@@ -0,0 +1,225 @@
+#!/bin/bash
+# SPDX-License-Identifier: GPL-2.0
+
+SYSFS=
+# Kselftest framework requirement - SKIP code is 4.
+ksft_skip=4
+retval=0
+
+prerequisite()
+{
+	msg="skip all tests:"
+
+	if [ $UID != 0 ]; then
+		echo $msg must be run as root >&2
+		exit $ksft_skip
+	fi
+
+	taskset -p 01 $$
+
+	SYSFS=`mount -t sysfs | head -1 | awk '{ print $3 }'`
+
+	if [ ! -d "$SYSFS" ]; then
+		echo $msg sysfs is not mounted >&2
+		exit $ksft_skip
+	fi
+
+	if ! ls $SYSFS/devices/system/cpu/cpu*/online > /dev/null 2>&1; then
+		echo $msg cpu hotplug is not supported >&2
+		exit $ksft_skip
+	fi
+
+	echo "CPU online/offline summary:"
+	online_cpus=`cat $SYSFS/devices/system/cpu/online`
+	online_max=${online_cpus##*-}
+
+	if [[ "$online_cpus" = "$online_max" ]]; then
+		echo "$msg: since there is only one cpu: $online_cpus"
+		exit $ksft_skip
+	fi
+
+	present_cpus=`cat $SYSFS/devices/system/cpu/present`
+	present_max=${present_cpus##*-}
+	echo "present_cpus = $present_cpus present_max = $present_max"
+
+	echo -e "\t Cpus in online state: $online_cpus"
+
+	offline_cpus=`cat $SYSFS/devices/system/cpu/offline`
+	if [[ "a$offline_cpus" = "a" ]]; then
+		offline_cpus=0
+	else
+		offline_max=${offline_cpus##*-}
+	fi
+	echo -e "\t Cpus in offline state: $offline_cpus"
+}
+
+#
+# list all hot-pluggable CPUs
+#
+hotpluggable_cpus()
+{
+	local state=${1:-.\*}
+
+	for cpu in $SYSFS/devices/system/cpu/cpu*; do
+		if [ -f $cpu/online ] && grep -q $state $cpu/online; then
+			echo ${cpu##/*/cpu}
+		fi
+	done
+}
+
+hotpluggable_offline_cpus()
+{
+	hotpluggable_cpus 0
+}
+
+hotpluggable_online_cpus()
+{
+	hotpluggable_cpus 1
+}
+
+cpu_is_online()
+{
+	grep -q 1 $SYSFS/devices/system/cpu/cpu$1/online
+}
+
+cpu_is_offline()
+{
+	grep -q 0 $SYSFS/devices/system/cpu/cpu$1/online
+}
+
+online_cpu()
+{
+	echo 1 > $SYSFS/devices/system/cpu/cpu$1/online
+}
+
+offline_cpu()
+{
+	echo 0 > $SYSFS/devices/system/cpu/cpu$1/online
+}
+
+online_cpu_expect_success()
+{
+	local cpu=$1
+
+	if ! online_cpu $cpu; then
+		echo $FUNCNAME $cpu: unexpected fail >&2
+		retval=1
+	elif ! cpu_is_online $cpu; then
+		echo $FUNCNAME $cpu: unexpected offline >&2
+		retval=1
+	fi
+}
+
+online_cpu_expect_fail()
+{
+	local cpu=$1
+
+	if online_cpu $cpu 2> /dev/null; then
+		echo $FUNCNAME $cpu: unexpected success >&2
+		retval=1
+	elif ! cpu_is_offline $cpu; then
+		echo $FUNCNAME $cpu: unexpected online >&2
+		retval=1
+	fi
+}
+
+offline_cpu_expect_success()
+{
+	local cpu=$1
+
+	if ! offline_cpu $cpu; then
+		echo $FUNCNAME $cpu: unexpected fail >&2
+		retval=1
+	elif ! cpu_is_offline $cpu; then
+		echo $FUNCNAME $cpu: unexpected offline >&2
+		retval=1
+	fi
+}
+
+offline_cpu_expect_fail()
+{
+	local cpu=$1
+
+	if offline_cpu $cpu 2> /dev/null; then
+		echo $FUNCNAME $cpu: unexpected success >&2
+		retval=1
+	elif ! cpu_is_online $cpu; then
+		echo $FUNCNAME $cpu: unexpected offline >&2
+		retval=1
+	fi
+}
+
+online_all_hot_pluggable_cpus()
+{
+	for cpu in `hotpluggable_offline_cpus`; do
+		online_cpu_expect_success $cpu
+	done
+}
+
+offline_all_hot_pluggable_cpus()
+{
+	local reserve_cpu=$online_max
+	for cpu in `hotpluggable_online_cpus`; do
+		# Reserve one cpu oneline at least.
+		if [ $cpu -eq $reserve_cpu ];then
+			continue
+		fi
+		offline_cpu_expect_success $cpu
+	done
+}
+
+allcpus=0
+online_cpus=0
+online_max=0
+offline_cpus=0
+offline_max=0
+present_cpus=0
+present_max=0
+
+while getopts ah opt; do
+	case $opt in
+	a)
+		allcpus=1
+		;;
+	h)
+		echo "Usage $0 [ -a ]"
+		echo -e "\t default offline one cpu"
+		echo -e "\t run with -a option to offline all cpus"
+		exit
+		;;
+	esac
+done
+
+prerequisite
+
+#
+# Safe test (default) - offline and online one cpu
+#
+if [ $allcpus -eq 0 ]; then
+	echo "Limited scope test: one hotplug cpu"
+	echo -e "\t (leaves cpu in the original state):"
+	echo -e "\t online to offline to online: cpu $online_max"
+	offline_cpu_expect_success $online_max
+	online_cpu_expect_success $online_max
+
+	if [[ $offline_cpus -gt 0 ]]; then
+		echo -e "\t online to offline to online: cpu $present_max"
+		online_cpu_expect_success $present_max
+		offline_cpu_expect_success $present_max
+		online_cpu $present_max
+	fi
+	exit $retval
+else
+	echo "Full scope test: all hotplug cpus"
+	echo -e "\t online all offline cpus"
+	echo -e "\t offline all online cpus"
+	echo -e "\t online all offline cpus"
+fi
+
+online_all_hot_pluggable_cpus
+
+offline_all_hot_pluggable_cpus
+
+online_all_hot_pluggable_cpus
+
+exit $retval