selftests: kmod: test disabling module autoloading

Test that request_module() fails with -ENOENT when
/proc/sys/kernel/modprobe contains (a) a nonexistent path, and (b) an
empty path.

Case (b) is a regression test for the patch "kmod: make request_module()
return an error when autoloading is disabled".

Tested with 'kmod.sh -t 0010 && kmod.sh -t 0011', and also simply with
'kmod.sh' to run all kmod tests.

Signed-off-by: Eric Biggers <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
Acked-by: Luis Chamberlain <[e-mail]>
Cc: Alexei Starovoitov <[e-mail]>
Cc: Greg Kroah-Hartman <[e-mail]>
Cc: Jeff Vander Stoep <[e-mail]>
Cc: Jessica Yu <[e-mail]>
Cc: Kees Cook <[e-mail]>
Cc: NeilBrown <[e-mail]>
Link: http://lkml.kernel.org/r/[e-mail]
Signed-off-by: Linus Torvalds <[e-mail]>

tools/testing/selftests/kmod/kmod.sh

···
 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"
 
 # Kselftest framework requirement - SKIP code is 4.
 ksft_skip=4
···
 
 test_finish()
 {
+	echo "$MODPROBE" > /proc/sys/kernel/modprobe
 	echo "Test completed"
 }
 
···
 	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
+}
+
 list_tests()
 {
 	echo "Test ID list:"
···
 	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"
 }
 
 usage()
···
 allow_user_defaults
 load_req_mod
 
+MODPROBE=$(</proc/sys/kernel/modprobe)
 trap "test_finish" EXIT
 
 parse_args $@