Commit 2810c1e99867 ("kunit: Fix wild-memory-access bug in
kunit_free_suite_set()") fixed a wild-memory-access bug that could have
happened during the loading phase of test suites built and executed as
loadable modules. However, it also introduced a problematic side effect
that causes test suites modules to crash when they attempt to register
fake devices.
When a module is loaded, it traverses the MODULE_STATE_UNFORMED and
MODULE_STATE_COMING states before reaching the normal operating state
MODULE_STATE_LIVE. Finally, when the module is removed, it moves to
MODULE_STATE_GOING before being released. However, if the loading
function load_module() fails between complete_formation() and
do_init_module(), the module goes directly from MODULE_STATE_COMING to
MODULE_STATE_GOING without passing through MODULE_STATE_LIVE.
This behavior was causing kunit_module_exit() to be called without
having first executed kunit_module_init(). Since kunit_module_exit() is
responsible for freeing the memory allocated by kunit_module_init()
through kunit_filter_suites(), this behavior was resulting in a
wild-memory-access bug.
Commit 2810c1e99867 ("kunit: Fix wild-memory-access bug in
kunit_free_suite_set()") fixed this issue by running the tests when the
module is still in MODULE_STATE_COMING. However, modules in that state
are not fully initialized, lacking sysfs kobjects. Therefore, if a test
module attempts to register a fake device, it will inevitably crash.
This patch proposes a different approach to fix the original
wild-memory-access bug while restoring the normal module execution flow
by making kunit_module_exit() able to detect if kunit_module_init() has
previously initialized the tests suite set. In this way, test modules
can once again register fake devices without crashing.
This behavior is achieved by checking whether mod->kunit_suites is a
virtual or direct mapping address. If it is a virtual address, then
kunit_module_init() has allocated the suite_set in kunit_filter_suites()
using kmalloc_array(). On the contrary, if mod->kunit_suites is still
pointing to the original address that was set when looking up the
.kunit_test_suites section of the module, then the loading phase has
failed and there's no memory to be freed.
v3:
- add a comment to clarify why the start address is checked
v2:
- add include <linux/mm.h>
Fixes: 2810c1e99867 ("kunit: Fix wild-memory-access bug in kunit_free_suite_set()")
Tested-by: Richard Fitzgerald <rf@xxxxxxxxxxxxxxxxxxxxx>
Reviewed-by: Javier Martinez Canillas <javierm@xxxxxxxxxx>
Signed-off-by: Marco Pagani <marpagan@xxxxxxxxxx>
---
lib/kunit/test.c | 14 +++++++++++---
1 file changed, 11 insertions(+), 3 deletions(-)
diff --git a/lib/kunit/test.c b/lib/kunit/test.c
index 7aceb07a1af9..3263e0d5e0f6 100644
--- a/lib/kunit/test.c
+++ b/lib/kunit/test.c
@@ -16,6 +16,7 @@
#include <linux/panic.h>
#include <linux/sched/debug.h>
#include <linux/sched.h>
+#include <linux/mm.h>
#include "debugfs.h"
#include "hooks-impl.h"
@@ -775,12 +776,19 @@ static void kunit_module_exit(struct module *mod)
};
const char *action = kunit_action();
+ /*
+ * Check if the start address is a valid virtual address to detect
+ * if the module load sequence has failed and the suite set has not
+ * been initialized and filtered.
+ */
+ if (!suite_set.start || !virt_addr_valid(suite_set.start))
+ return;
+
if (!action)
__kunit_test_suites_exit(mod->kunit_suites,
mod->num_kunit_suites);
- if (suite_set.start)
- kunit_free_suite_set(suite_set);
+ kunit_free_suite_set(suite_set);
}
static int kunit_module_notify(struct notifier_block *nb, unsigned long val,
@@ -790,12 +798,12 @@ static int kunit_module_notify(struct notifier_block *nb, unsigned long val,
switch (val) {
case MODULE_STATE_LIVE:
+ kunit_module_init(mod);
break;
case MODULE_STATE_GOING:
kunit_module_exit(mod);
break;
case MODULE_STATE_COMING:
- kunit_module_init(mod);
break;
case MODULE_STATE_UNFORMED:
break;
base-commit: 33cc938e65a98f1d29d0a18403dbbee050dcad9a
--
2.43.0
