[PATCH] lkdtm: clean up sparse warnings

[Kees Cook]

Since lkdtm intentionally does "bad" things, we need to convince sparse
that we're doing these things on purpose. This adds an explicit cast
to the call to copy_to_user() and marks the spin lock as expecting
to dead-lock.

Reported-by: Fengguang Wu <fengguang.wu@xxxxxxxxx>
Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx>
---
 drivers/misc/lkdtm.c |    5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/misc/lkdtm.c b/drivers/misc/lkdtm.c
index a2edb2ee0921..a9a203d5f8d9 100644
--- a/drivers/misc/lkdtm.c
+++ b/drivers/misc/lkdtm.c
@@ -334,9 +334,10 @@ static void execute_location(void *dst)
 
 static void execute_user_location(void *dst)
 {
+	/* Intentionally crossing kernel/user memory boundary. */
 	void (*func)(void) = dst;
 
-	if (copy_to_user(dst, do_nothing, EXEC_SIZE))
+	if (copy_to_user((void __user *)dst, do_nothing, EXEC_SIZE))
 		return;
 	func();
 }
@@ -408,6 +409,8 @@ static void lkdtm_do_action(enum ctype which)
 	case CT_SPINLOCKUP:
 		/* Must be called twice to trigger. */
 		spin_lock(&lock_me_up);
+		/* Let sparse know we intended to exit holding the lock. */
+		__release(&lock_me_up);
 		break;
 	case CT_HUNG_TASK:
 		set_current_state(TASK_UNINTERRUPTIBLE);
-- 
1.7.9.5


-- 
Kees Cook
Chrome OS Security
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