The do_usercopy_stack() function uses uninitialized stack data to initialize
more of the stack, which causes a warning in some configurations (ARM
allmodconfig):
drivers/misc/lkdtm_usercopy.c:52:15: warning: 'bad_stack' may be used
uninitialized in this function [-Wmaybe-uninitialized]
The warning gets reports by Mark Brown's build bot and looks correct (we are
trying
to trick the compiler here, and sometimes the compiler notices), and I could
reproduce
it with gcc-4.7 through gcc-5.3 but not gcc-6.1 for some reason.
This changes the code to use the low byte of the address of the stack to
initialize
the stack data, instead of using data from the stack itself, to avoid the
warning.
Signed-off-by: Arnd Bergmann <a...@arndb.de>
Fixes: a3dff71c1c88 ("lkdtm: split usercopy tests to separate file")
---
drivers/misc/lkdtm_usercopy.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/misc/lkdtm_usercopy.c b/drivers/misc/lkdtm_usercopy.c
index 5a3fd76eec27..5525a204db93 100644
--- a/drivers/misc/lkdtm_usercopy.c
+++ b/drivers/misc/lkdtm_usercopy.c
@@ -49,7 +49,7 @@ static noinline void do_usercopy_stack(bool to_user, bool
bad_frame)
/* This is a pointer to outside our current stack frame. */
if (bad_frame) {
- bad_stack = do_usercopy_stack_callee((uintptr_t)bad_stack);
+ bad_stack = do_usercopy_stack_callee((uintptr_t)&bad_stack);
} else {
/* Put start address just inside stack. */
bad_stack = task_stack_page(current) + THREAD_SIZE;
--
2.9.0
