ftrace: Synchronize the initialization of ftrace_opsgrafted

There's some internal state that ftrace_ops needs to have set, but since
it can be declared outside of the ftrace.c code, it calls
ftrace_ops_init() on the ops in every global function. The issue is that
if two tasks call it on the same ops at the same time it is possible to
have the initialization of one corrupt the initialization of the other
call.

Create a ops_mutex to use to synchronize every initialization of the
ftrace_ops. The mutex is taken within checking the ftrace_ops flag that
states it was initializied but the flag is checked again after the mutex
has been taken. Checking first outside the mutex allows it to shortcut
having to take the mutex. But then the check needs to be done again after
the mute is taken in case of races.

Cc: stable@vger.kernel.org
Link: https://patch.msgid.link/20260902095501.6b59af20@gandalf.local.home
Fixes: f04f24fb7e48d ("ftrace, kprobes: Fix a deadlock on ftrace_regex_lock")
Reported-by: sashiko-bot@kernel.org
Close: https://lore.kernel.org/all/20260829025528.49A831F000E9@smtp.kernel.org/
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

3 files changed, 692 insertions, 0 deletions

diff --git a/tools/testing/selftests/kmod/Makefile b/tools/testing/selftests/kmod/Makefile
new file mode 100644
index 000000000..5b3e746a0
--- /dev/null
+++ b/tools/testing/selftests/kmod/Makefile
@@ -0,0 +1,12 @@
+# SPDX-License-Identifier: GPL-2.0-only
+# Makefile for kmod loading selftests
+
+# No binaries, but make sure arg-less "make" doesn't trigger "run_tests"
+all:
+
+TEST_PROGS := kmod.sh
+
+include ../lib.mk
+
+# Nothing to clean up.
+clean:
diff --git a/tools/testing/selftests/kmod/config b/tools/testing/selftests/kmod/config
new file mode 100644
index 000000000..1f1e63494
--- /dev/null
+++ b/tools/testing/selftests/kmod/config
@@ -0,0 +1,2 @@
+CONFIG_TEST_KMOD=m
+CONFIG_TEST_LKM=m
diff --git a/tools/testing/selftests/kmod/kmod.sh b/tools/testing/selftests/kmod/kmod.sh
new file mode 100755
index 000000000..7189715d7
--- /dev/null
+++ b/tools/testing/selftests/kmod/kmod.sh
@@ -0,0 +1,678 @@
+#!/bin/bash
+# SPDX-License-Identifier: GPL-2.0-or-later OR copyleft-next-0.3.1
+# Copyright (C) 2017 Luis R. Rodriguez <mcgrof@kernel.org>
+#
+# This is a stress test script for kmod, the kernel module loader. It uses
+# test_kmod which exposes a series of knobs for the API for us so we can
+# tweak each test in userspace rather than in kernelspace.
+#
+# The way kmod works is it uses the kernel's usermode helper API to eventually
+# call /sbin/modprobe. It has a limit of the number of concurrent calls
+# possible. The kernel interface to load modules is request_module(), however
+# mount uses get_fs_type(). Both behave slightly differently, but the
+# differences are important enough to test each call separately. For this
+# reason test_kmod starts by providing tests for both calls.
+#
+# The test driver test_kmod assumes a series of defaults which you can
+# override by exporting to your environment prior running this script.
+# For instance this script assumes you do not have xfs loaded upon boot.
+# If this is false, export DEFAULT_KMOD_FS="ext4" prior to running this
+# script if the filesystem module you don't have loaded upon bootup
+# is ext4 instead. Refer to allow_user_defaults() for a list of user
+# override variables possible.
+#
+# You'll want at least 4 GiB of RAM to expect to run these tests
+# without running out of memory on them. For other requirements refer
+# to test_reqs()
+
+set -e
+
+TEST_NAME="kmod"
+TEST_DRIVER="test_${TEST_NAME}"
+TEST_DIR=$(dirname $0)
+
+# This represents
+#
+# TEST_ID:TEST_COUNT:ENABLED
+#
+# TEST_ID: is the test id number
+# TEST_COUNT: number of times we should run the test
+# ENABLED: 1 if enabled, 0 otherwise
+#
+# Once these are enabled please leave them as-is. Write your own test,
+# we have tons of space.
+ALL_TESTS="0001:3:1"
+ALL_TESTS="$ALL_TESTS 0002:3:1"
+ALL_TESTS="$ALL_TESTS 0003:1:1"
+ALL_TESTS="$ALL_TESTS 0004:1:1"
+ALL_TESTS="$ALL_TESTS 0005:10:1"
+ALL_TESTS="$ALL_TESTS 0006:10:1"
+ALL_TESTS="$ALL_TESTS 0007:5:1"
+ALL_TESTS="$ALL_TESTS 0008:150:1"
+ALL_TESTS="$ALL_TESTS 0009:150:1"
+ALL_TESTS="$ALL_TESTS 0010:1:1"
+ALL_TESTS="$ALL_TESTS 0011:1:1"
+ALL_TESTS="$ALL_TESTS 0012:1:1"
+ALL_TESTS="$ALL_TESTS 0013:1:1"
+
+# Kselftest framework requirement - SKIP code is 4.
+ksft_skip=4
+
+test_modprobe()
+{
+       if [ ! -d $DIR ]; then
+               echo "$0: $DIR not present" >&2
+               echo "You must have the following enabled in your kernel:" >&2
+               cat $TEST_DIR/config >&2
+               exit $ksft_skip
+       fi
+}
+
+function allow_user_defaults()
+{
+	if [ -z $DEFAULT_KMOD_DRIVER ]; then
+		DEFAULT_KMOD_DRIVER="test_module"
+	fi
+
+	if [ -z $DEFAULT_KMOD_FS ]; then
+		DEFAULT_KMOD_FS="xfs"
+	fi
+
+	if [ -z $PROC_DIR ]; then
+		PROC_DIR="/proc/sys/kernel/"
+	fi
+
+	if [ -z $MODPROBE_LIMIT ]; then
+		MODPROBE_LIMIT=50
+	fi
+
+	if [ -z $DIR ]; then
+		DIR="/sys/devices/virtual/misc/${TEST_DRIVER}0/"
+	fi
+
+	if [ -z $DEFAULT_NUM_TESTS ]; then
+		DEFAULT_NUM_TESTS=150
+	fi
+
+	MODPROBE_LIMIT_FILE="${PROC_DIR}/kmod-limit"
+}
+
+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 $ksft_skip
+	fi
+
+	# kmod 19 has a bad bug where it returns 0 when modprobe
+	# gets called *even* if the module was not loaded due to
+	# some bad heuristics. For details see:
+	#
+	# A work around is possible in-kernel but its rather
+	# complex.
+	KMOD_VERSION=$(kmod --version | awk '{print $3}')
+	if [[ $KMOD_VERSION  -le 19 ]]; then
+		echo "$0: You need at least kmod 20" >&2
+		echo "kmod <= 19 is buggy, for details see:" >&2
+		echo "https://git.kernel.org/cgit/utils/kernel/kmod/kmod.git/commit/libkmod/libkmod-module.c?id=fd44a98ae2eb5eb32161088954ab21e58e19dfc4" >&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
+}
+
+function load_req_mod()
+{
+	trap "test_modprobe" EXIT
+
+	if [ ! -d $DIR ]; then
+		# Alanis: "Oh isn't it ironic?"
+		modprobe $TEST_DRIVER
+	fi
+}
+
+test_finish()
+{
+	echo "$MODPROBE" > /proc/sys/kernel/modprobe
+	echo "Test completed"
+}
+
+errno_name_to_val()
+{
+	case "$1" in
+	# kmod calls modprobe and upon of a module not found
+	# modprobe returns just 1... However in the kernel we
+	# *sometimes* see 256...
+	MODULE_NOT_FOUND)
+		echo 256;;
+	SUCCESS)
+		echo 0;;
+	-EPERM)
+		echo -1;;
+	-ENOENT)
+		echo -2;;
+	-EINVAL)
+		echo -22;;
+	-ERR_ANY)
+		echo -123456;;
+	*)
+		echo invalid;;
+	esac
+}
+
+errno_val_to_name()
+	case "$1" in
+	256)
+		echo MODULE_NOT_FOUND;;
+	0)
+		echo SUCCESS;;
+	-1)
+		echo -EPERM;;
+	-2)
+		echo -ENOENT;;
+	-22)
+		echo -EINVAL;;
+	-123456)
+		echo -ERR_ANY;;
+	*)
+		echo invalid;;
+	esac
+
+config_set_test_case_driver()
+{
+	if ! echo -n 1 >$DIR/config_test_case; then
+		echo "$0: Unable to set to test case to driver" >&2
+		exit 1
+	fi
+}
+
+config_set_test_case_fs()
+{
+	if ! echo -n 2 >$DIR/config_test_case; then
+		echo "$0: Unable to set to test case to fs" >&2
+		exit 1
+	fi
+}
+
+config_num_threads()
+{
+	if ! echo -n $1 >$DIR/config_num_threads; then
+		echo "$0: Unable to set to number of threads" >&2
+		exit 1
+	fi
+}
+
+config_get_modprobe_limit()
+{
+	if [[ -f ${MODPROBE_LIMIT_FILE} ]] ; then
+		MODPROBE_LIMIT=$(cat $MODPROBE_LIMIT_FILE)
+	fi
+	echo $MODPROBE_LIMIT
+}
+
+config_num_thread_limit_extra()
+{
+	MODPROBE_LIMIT=$(config_get_modprobe_limit)
+	let EXTRA_LIMIT=$MODPROBE_LIMIT+$1
+	config_num_threads $EXTRA_LIMIT
+}
+
+# For special characters use printf directly,
+# refer to kmod_test_0001
+config_set_driver()
+{
+	if ! echo -n $1 >$DIR/config_test_driver; then
+		echo "$0: Unable to set driver" >&2
+		exit 1
+	fi
+}
+
+config_set_fs()
+{
+	if ! echo -n $1 >$DIR/config_test_fs; then
+		echo "$0: Unable to set driver" >&2
+		exit 1
+	fi
+}
+
+config_get_driver()
+{
+	cat $DIR/config_test_driver
+}
+
+config_get_test_result()
+{
+	cat $DIR/test_result
+}
+
+config_reset()
+{
+	if ! echo -n "1" >"$DIR"/reset; then
+		echo "$0: reset should have worked" >&2
+		exit 1
+	fi
+}
+
+config_show_config()
+{
+	echo "----------------------------------------------------"
+	cat "$DIR"/config
+	echo "----------------------------------------------------"
+}
+
+config_trigger()
+{
+	if ! echo -n "1" >"$DIR"/trigger_config 2>/dev/null; then
+		echo "$1: FAIL - loading should have worked"
+		config_show_config
+		exit 1
+	fi
+	echo "$1: OK! - loading kmod test"
+}
+
+config_trigger_want_fail()
+{
+	if echo "1" > $DIR/trigger_config 2>/dev/null; then
+		echo "$1: FAIL - test case was expected to fail"
+		config_show_config
+		exit 1
+	fi
+	echo "$1: OK! - kmod test case failed as expected"
+}
+
+config_expect_result()
+{
+	RC=$(config_get_test_result)
+	RC_NAME=$(errno_val_to_name $RC)
+
+	ERRNO_NAME=$2
+	ERRNO=$(errno_name_to_val $ERRNO_NAME)
+
+	if [[ $ERRNO_NAME = "-ERR_ANY" ]]; then
+		if [[ $RC -ge 0 ]]; then
+			echo "$1: FAIL, test expects $ERRNO_NAME - got $RC_NAME ($RC)" >&2
+			config_show_config
+			exit 1
+		fi
+	elif [[ $RC != $ERRNO ]]; then
+		echo "$1: FAIL, test expects $ERRNO_NAME ($ERRNO) - got $RC_NAME ($RC)" >&2
+		config_show_config
+		exit 1
+	fi
+	echo "$1: OK! - Return value: $RC ($RC_NAME), expected $ERRNO_NAME"
+}
+
+kmod_defaults_driver()
+{
+	config_reset
+	modprobe -r $DEFAULT_KMOD_DRIVER
+	config_set_driver $DEFAULT_KMOD_DRIVER
+}
+
+kmod_defaults_fs()
+{
+	config_reset
+	modprobe -r $DEFAULT_KMOD_FS
+	config_set_fs $DEFAULT_KMOD_FS
+	config_set_test_case_fs
+}
+
+kmod_test_0001_driver()
+{
+	NAME='\000'
+
+	kmod_defaults_driver
+	config_num_threads 1
+	printf $NAME >"$DIR"/config_test_driver
+	config_trigger ${FUNCNAME[0]}
+	config_expect_result ${FUNCNAME[0]} MODULE_NOT_FOUND
+}
+
+kmod_test_0001_fs()
+{
+	NAME='\000'
+
+	kmod_defaults_fs
+	config_num_threads 1
+	printf $NAME >"$DIR"/config_test_fs
+	config_trigger ${FUNCNAME[0]}
+	config_expect_result ${FUNCNAME[0]} -EINVAL
+}
+
+kmod_test_0001()
+{
+	kmod_test_0001_driver
+	kmod_test_0001_fs
+}
+
+kmod_test_0002_driver()
+{
+	NAME="nope-$DEFAULT_KMOD_DRIVER"
+
+	kmod_defaults_driver
+	config_set_driver $NAME
+	config_num_threads 1
+	config_trigger ${FUNCNAME[0]}
+	config_expect_result ${FUNCNAME[0]} MODULE_NOT_FOUND
+}
+
+kmod_test_0002_fs()
+{
+	NAME="nope-$DEFAULT_KMOD_FS"
+
+	kmod_defaults_fs
+	config_set_fs $NAME
+	config_trigger ${FUNCNAME[0]}
+	config_expect_result ${FUNCNAME[0]} -EINVAL
+}
+
+kmod_test_0002()
+{
+	kmod_test_0002_driver
+	kmod_test_0002_fs
+}
+
+kmod_test_0003()
+{
+	kmod_defaults_fs
+	config_num_threads 1
+	config_trigger ${FUNCNAME[0]}
+	config_expect_result ${FUNCNAME[0]} SUCCESS
+}
+
+kmod_test_0004()
+{
+	kmod_defaults_fs
+	config_num_threads 2
+	config_trigger ${FUNCNAME[0]}
+	config_expect_result ${FUNCNAME[0]} SUCCESS
+}
+
+kmod_test_0005()
+{
+	kmod_defaults_driver
+	config_trigger ${FUNCNAME[0]}
+	config_expect_result ${FUNCNAME[0]} SUCCESS
+}
+
+kmod_test_0006()
+{
+	kmod_defaults_fs
+	config_trigger ${FUNCNAME[0]}
+	config_expect_result ${FUNCNAME[0]} SUCCESS
+}
+
+kmod_test_0007()
+{
+	kmod_test_0005
+	kmod_test_0006
+}
+
+kmod_test_0008()
+{
+	kmod_defaults_driver
+	MODPROBE_LIMIT=$(config_get_modprobe_limit)
+	let EXTRA=$MODPROBE_LIMIT/6
+	config_num_thread_limit_extra $EXTRA
+	config_trigger ${FUNCNAME[0]}
+	config_expect_result ${FUNCNAME[0]} SUCCESS
+}
+
+kmod_test_0009()
+{
+	kmod_defaults_fs
+	MODPROBE_LIMIT=$(config_get_modprobe_limit)
+	let EXTRA=$MODPROBE_LIMIT/4
+	config_num_thread_limit_extra $EXTRA
+	config_trigger ${FUNCNAME[0]}
+	config_expect_result ${FUNCNAME[0]} SUCCESS
+}
+
+kmod_test_0010()
+{
+	kmod_defaults_driver
+	config_num_threads 1
+	echo "/KMOD_TEST_NONEXISTENT" > /proc/sys/kernel/modprobe
+	config_trigger ${FUNCNAME[0]}
+	config_expect_result ${FUNCNAME[0]} -ENOENT
+	echo "$MODPROBE" > /proc/sys/kernel/modprobe
+}
+
+kmod_test_0011()
+{
+	kmod_defaults_driver
+	config_num_threads 1
+	# This causes the kernel to not even try executing modprobe.  The error
+	# code is still -ENOENT like when modprobe doesn't exist, so we can't
+	# easily test for the exact difference.  But this still is a useful test
+	# since there was a bug where request_module() returned 0 in this case.
+	echo > /proc/sys/kernel/modprobe
+	config_trigger ${FUNCNAME[0]}
+	config_expect_result ${FUNCNAME[0]} -ENOENT
+	echo "$MODPROBE" > /proc/sys/kernel/modprobe
+}
+
+kmod_check_visibility()
+{
+	local name="$1"
+	local cmd="$2"
+
+	modprobe $DEFAULT_KMOD_DRIVER
+
+	local priv=$(eval $cmd)
+	local unpriv=$(capsh --drop=CAP_SYSLOG -- -c "$cmd")
+
+	if [ "$priv" = "$unpriv" ] || \
+	   [ "${priv:0:3}" = "0x0" ] || \
+	   [ "${unpriv:0:3}" != "0x0" ] ; then
+		echo "${FUNCNAME[0]}: FAIL, $name visible to unpriv: '$priv' vs '$unpriv'" >&2
+		exit 1
+	else
+		echo "${FUNCNAME[0]}: OK!"
+	fi
+}
+
+kmod_test_0012()
+{
+	kmod_check_visibility /proc/modules \
+		"grep '^${DEFAULT_KMOD_DRIVER}\b' /proc/modules | awk '{print \$NF}'"
+}
+
+kmod_test_0013()
+{
+	kmod_check_visibility '/sys/module/*/sections/*' \
+		"cat /sys/module/${DEFAULT_KMOD_DRIVER}/sections/.*text | head -n1"
+}
+
+list_tests()
+{
+	echo "Test ID list:"
+	echo
+	echo "TEST_ID x NUM_TEST"
+	echo "TEST_ID:   Test ID"
+	echo "NUM_TESTS: Number of recommended times to run the test"
+	echo
+	echo "0001 x $(get_test_count 0001) - Simple test - 1 thread  for empty string"
+	echo "0002 x $(get_test_count 0002) - Simple test - 1 thread  for modules/filesystems that do not exist"
+	echo "0003 x $(get_test_count 0003) - Simple test - 1 thread  for get_fs_type() only"
+	echo "0004 x $(get_test_count 0004) - Simple test - 2 threads for get_fs_type() only"
+	echo "0005 x $(get_test_count 0005) - multithreaded tests with default setup - request_module() only"
+	echo "0006 x $(get_test_count 0006) - multithreaded tests with default setup - get_fs_type() only"
+	echo "0007 x $(get_test_count 0007) - multithreaded tests with default setup test request_module() and get_fs_type()"
+	echo "0008 x $(get_test_count 0008) - multithreaded - push kmod_concurrent over max_modprobes for request_module()"
+	echo "0009 x $(get_test_count 0009) - multithreaded - push kmod_concurrent over max_modprobes for get_fs_type()"
+	echo "0010 x $(get_test_count 0010) - test nonexistent modprobe path"
+	echo "0011 x $(get_test_count 0011) - test completely disabling module autoloading"
+	echo "0012 x $(get_test_count 0012) - test /proc/modules address visibility under CAP_SYSLOG"
+	echo "0013 x $(get_test_count 0013) - test /sys/module/*/sections/* visibility under CAP_SYSLOG"
+}
+
+usage()
+{
+	NUM_TESTS=$(grep -o ' ' <<<"$ALL_TESTS" | grep -c .)
+	let NUM_TESTS=$NUM_TESTS+1
+	MAX_TEST=$(printf "%04d\n" $NUM_TESTS)
+	echo "Usage: $0 [ -t <4-number-digit> ] | [ -w <4-number-digit> ] |"
+	echo "		 [ -s <4-number-digit> ] | [ -c <4-number-digit> <test- count>"
+	echo "           [ all ] [ -h | --help ] [ -l ]"
+	echo ""
+	echo "Valid tests: 0001-$MAX_TEST"
+	echo ""
+	echo "    all     Runs all tests (default)"
+	echo "    -t      Run test ID the number amount of times is recommended"
+	echo "    -w      Watch test ID run until it runs into an error"
+	echo "    -s      Run test ID once"
+	echo "    -c      Run test ID x test-count number of times"
+	echo "    -l      List all test ID list"
+	echo " -h|--help  Help"
+	echo
+	echo "If an error every occurs execution will immediately terminate."
+	echo "If you are adding a new test try using -w <test-ID> first to"
+	echo "make sure the test passes a series of tests."
+	echo
+	echo Example uses:
+	echo
+	echo "${TEST_NAME}.sh		-- executes all tests"
+	echo "${TEST_NAME}.sh -t 0008	-- Executes test ID 0008 number of times is recommended"
+	echo "${TEST_NAME}.sh -w 0008	-- Watch test ID 0008 run until an error occurs"
+	echo "${TEST_NAME}.sh -s 0008	-- Run test ID 0008 once"
+	echo "${TEST_NAME}.sh -c 0008 3	-- Run test ID 0008 three times"
+	echo
+	list_tests
+	exit 1
+}
+
+function test_num()
+{
+	re='^[0-9]+$'
+	if ! [[ $1 =~ $re ]]; then
+		usage
+	fi
+}
+
+function get_test_data()
+{
+	test_num $1
+	local field_num=$(echo $1 | sed 's/^0*//')
+	echo $ALL_TESTS | awk '{print $'$field_num'}'
+}
+
+function get_test_count()
+{
+	TEST_DATA=$(get_test_data $1)
+	LAST_TWO=${TEST_DATA#*:*}
+	echo ${LAST_TWO%:*}
+}
+
+function get_test_enabled()
+{
+	TEST_DATA=$(get_test_data $1)
+	echo ${TEST_DATA#*:*:}
+}
+
+function run_all_tests()
+{
+	for i in $ALL_TESTS ; do
+		TEST_ID=${i%:*:*}
+		ENABLED=$(get_test_enabled $TEST_ID)
+		TEST_COUNT=$(get_test_count $TEST_ID)
+		if [[ $ENABLED -eq "1" ]]; then
+			test_case $TEST_ID $TEST_COUNT
+		fi
+	done
+}
+
+function watch_log()
+{
+	if [ $# -ne 3 ]; then
+		clear
+	fi
+	date
+	echo "Running test: $2 - run #$1"
+}
+
+function watch_case()
+{
+	i=0
+	while [ 1 ]; do
+
+		if [ $# -eq 1 ]; then
+			test_num $1
+			watch_log $i ${TEST_NAME}_test_$1
+			${TEST_NAME}_test_$1
+		else
+			watch_log $i all
+			run_all_tests
+		fi
+		let i=$i+1
+	done
+}
+
+function test_case()
+{
+	NUM_TESTS=$DEFAULT_NUM_TESTS
+	if [ $# -eq 2 ]; then
+		NUM_TESTS=$2
+	fi
+
+	i=0
+	while [ $i -lt $NUM_TESTS ]; do
+		test_num $1
+		watch_log $i ${TEST_NAME}_test_$1 noclear
+		RUN_TEST=${TEST_NAME}_test_$1
+		$RUN_TEST
+		let i=$i+1
+	done
+}
+
+function parse_args()
+{
+	if [ $# -eq 0 ]; then
+		run_all_tests
+	else
+		if [[ "$1" = "all" ]]; then
+			run_all_tests
+		elif [[ "$1" = "-w" ]]; then
+			shift
+			watch_case $@
+		elif [[ "$1" = "-t" ]]; then
+			shift
+			test_num $1
+			test_case $1 $(get_test_count $1)
+		elif [[ "$1" = "-c" ]]; then
+			shift
+			test_num $1
+			test_num $2
+			test_case $1 $2
+		elif [[ "$1" = "-s" ]]; then
+			shift
+			test_case $1 1
+		elif [[ "$1" = "-l" ]]; then
+			list_tests
+		elif [[ "$1" = "-h" || "$1" = "--help" ]]; then
+			usage
+		else
+			usage
+		fi
+	fi
+}
+
+test_reqs
+allow_user_defaults
+load_req_mod
+
+MODPROBE=$(</proc/sys/kernel/modprobe)
+trap "test_finish" EXIT
+
+parse_args $@
+
+exit 0