test: add minimal module for verification testing

This is a pair of test modules I'd like to see in the tree.  Instead of
putting these in lkdtm, where I've been adding various tests that trigger
crashes, these don't make sense there since they need to be either
distinctly separate, or their pass/fail state don't need to crash the
machine.

These live in lib/ for now, along with a few other in-kernel test modules,
and use the slightly more common "test_" naming convention, instead of
"test-".  We should likely standardize on the former:

$ find . -name 'test_*.c' | grep -v /tools/ | wc -l
4
$ find . -name 'test-*.c' | grep -v /tools/ | wc -l
2

The first is entirely a no-op module, designed to allow simple testing of
the module loading and verification interface.  It's useful to have a
module that has no other uses or dependencies so it can be reliably used
for just testing module loading and verification.

The second is a module that exercises the user memory access functions, in
an effort to make sure that we can quickly catch any regressions in
boundary checking (e.g.  like what was recently fixed on ARM).

This patch (of 2):

When doing module loading verification tests (for example, with module
signing, or LSM hooks), it is very handy to have a module that can be
built on all systems under test, isn't auto-loaded at boot, and has no
device or similar dependencies.  This creates the "test_module.ko" module
for that purpose, which only reports its load and unload to printk.

Signed-off-by: Kees Cook <keescook@chromium.org>
Acked-by: Rusty Russell <rusty@rustcorp.com.au>
Cc: Joe Perches <joe@perches.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index db25707aa41bc021b8174391091178b85258d466..81882335c625ced244383ba53e9f9ac4ab6fb9d3 100644 (file)
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -1578,6 +1578,20 @@ config DMA_API_DEBUG
          This option causes a performance degredation.  Use only if you want
          to debug device drivers. If unsure, say N.
 
+config TEST_MODULE
+       tristate "Test module loading with 'hello world' module"
+       default n
+       depends on m
+       help
+         This builds the "test_module" module that emits "Hello, world"
+         on printk when loaded. It is designed to be used for basic
+         evaluation of the module loading subsystem (for example when
+         validating module verification). It lacks any extra dependencies,
+         and will not normally be loaded by the system unless explicitly
+         requested by name.
+
+         If unsure, say N.
+
 source "samples/Kconfig"
 
 source "lib/Kconfig.kgdb"

diff --git a/lib/Makefile b/lib/Makefile
index a459c31e8c6bb0286237b27bcb65d776bccad1b7..b494b9af631ce0f92ce2ecbc14dd1b7da800a6de 100644 (file)
--- a/lib/Makefile
+++ b/lib/Makefile
@@ -31,6 +31,7 @@ obj-y += string_helpers.o
 obj-$(CONFIG_TEST_STRING_HELPERS) += test-string_helpers.o
 obj-y += kstrtox.o
 obj-$(CONFIG_TEST_KSTRTOX) += test-kstrtox.o
+obj-$(CONFIG_TEST_MODULE) += test_module.o
 
 ifeq ($(CONFIG_DEBUG_KOBJECT),y)
 CFLAGS_kobject.o += -DDEBUG

diff --git a/lib/test_module.c b/lib/test_module.c
new file mode 100644 (file)
index 0000000..319b66f
--- /dev/null
+++ b/lib/test_module.c
@@ -0,0 +1,33 @@
+/*
+ * This module emits "Hello, world" on printk when loaded.
+ *
+ * It is designed to be used for basic evaluation of the module loading
+ * subsystem (for example when validating module signing/verification). It
+ * lacks any extra dependencies, and will not normally be loaded by the
+ * system unless explicitly requested by name.
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/init.h>
+#include <linux/module.h>
+#include <linux/printk.h>
+
+static int __init test_module_init(void)
+{
+       pr_warn("Hello, world\n");
+
+       return 0;
+}
+
+module_init(test_module_init);
+
+static void __exit test_module_exit(void)
+{
+       pr_warn("Goodbye\n");
+}
+
+module_exit(test_module_exit);
+
+MODULE_AUTHOR("Kees Cook <keescook@chromium.org>");
+MODULE_LICENSE("GPL");