Re: request_module DoS

[Luis Chamberlain <mcgrof@kernel.org>]

On Sat, May 07, 2022 at 01:02:20AM -0700, Luis Chamberlain wrote:
> You can try to reproduce by using adding a new test type for crypto-aegis256
> on lib/test_kmod.c. These tests however can try something similar but other
> modules.
> 
> /tools/testing/selftests/kmod/kmod.sh -t 0008
> /tools/testing/selftests/kmod/kmod.sh -t 0009
> 
> I can't decipher this yet.

Without testing it... but something like this might be an easier
reproducer:

diff --git a/tools/testing/selftests/kmod/kmod.sh b/tools/testing/selftests/kmod/kmod.sh
index afd42387e8b2..48b6b5ec6c1e 100755
--- a/tools/testing/selftests/kmod/kmod.sh
+++ b/tools/testing/selftests/kmod/kmod.sh
@@ -41,6 +41,7 @@ set -e
 TEST_NAME="kmod"
 TEST_DRIVER="test_${TEST_NAME}"
 TEST_DIR=$(dirname $0)
+PROC_CONFIG="/proc/config.gz"
 
 # This represents
 #
@@ -65,6 +66,7 @@ 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"
+ALL_TESTS="$ALL_TESTS 0014:150:1"
 
 # Kselftest framework requirement - SKIP code is 4.
 ksft_skip=4
@@ -79,6 +81,19 @@ test_modprobe()
        fi
 }
 
+kconfig_has()
+{
+	if [ -f $PROC_CONFIG ]; then
+		if zgrep -q $1 $PROC_CONFIG 2>/dev/null; then
+			echo "yes"
+		else
+			echo "no"
+		fi
+	else
+			echo "no"
+	fi
+}
+
 function allow_user_defaults()
 {
 	if [ -z $DEFAULT_KMOD_DRIVER ]; then
@@ -106,6 +121,8 @@ function allow_user_defaults()
 	fi
 
 	MODPROBE_LIMIT_FILE="${PROC_DIR}/kmod-limit"
+	HAS_CRYPTO_AEGIS256_MOD="$(kconfig_has CONFIG_CRYPTO_AEGIS256=m)"
+	HAS_CRYPTO_AEGIS256_BUILTIN="$(kconfig_has CONFIG_CRYPTO_AEGIS256=y)"
 }
 
 test_reqs()
@@ -504,6 +521,21 @@ kmod_test_0013()
 		"cat /sys/module/${DEFAULT_KMOD_DRIVER}/sections/.*text | head -n1"
 }
 
+kmod_test_0014()
+{
+	kmod_defaults_driver
+	MODPROBE_LIMIT=$(config_get_modprobe_limit)
+	let EXTRA=$MODPROBE_LIMIT/6
+	config_set_driver crypto-aegis256
+	config_num_thread_limit_extra $EXTRA
+	config_trigger ${FUNCNAME[0]}
+	if [[ "$HAS_CRYPTO_AEGIS256_MOD" == "yes" || "$HAS_CRYPTO_AEGIS256_BUILTIN" == "yes" ]]; then
+		config_expect_result ${FUNCNAME[0]} SUCCESS
+	else
+		config_expect_result ${FUNCNAME[0]} MODULE_NOT_FOUND
+	fi
+}
+
 list_tests()
 {
 	echo "Test ID list:"
@@ -525,6 +557,7 @@ list_tests()
 	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"
+	echo "0014 x $(get_test_count 0014) - multithreaded - push kmod_concurrent over max_modprobes for request_module() for crypto-aegis256"
 }
 
 usage()