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 <ebiggers@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Acked-by: Luis Chamberlain <mcgrof@kernel.org>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Jeff Vander Stoep <jeffv@google.com>
Cc: Jessica Yu <jeyu@kernel.org>
Cc: Kees Cook <keescook@chromium.org>
Cc: NeilBrown <neilb@suse.com>
Link: http://lkml.kernel.org/r/20200312202552.241885-5-ebiggers@kernel.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/tools/testing/selftests/kmod/kmod.sh b/tools/testing/selftests/kmod/kmod.sh
index 315a431..3702dbc 100755 (executable)
--- a/tools/testing/selftests/kmod/kmod.sh
+++ b/tools/testing/selftests/kmod/kmod.sh
@@ -61,6 +61,8 @@ 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"
 
 # Kselftest framework requirement - SKIP code is 4.
 ksft_skip=4
@@ -149,6 +151,7 @@ function load_req_mod()
 
 test_finish()
 {
+       echo "$MODPROBE" > /proc/sys/kernel/modprobe
        echo "Test completed"
 }
 
@@ -443,6 +446,30 @@ kmod_test_0009()
        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:"
@@ -460,6 +487,8 @@ list_tests()
        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()
@@ -616,6 +645,7 @@ test_reqs
 allow_user_defaults
 load_req_mod
 
+MODPROBE=$(</proc/sys/kernel/modprobe)
 trap "test_finish" EXIT
 
 parse_args $@