On Tue, Jul 26, 2016 at 5:28 AM, Arnd Bergmann <[email protected]> wrote: > 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 <[email protected]> > Fixes: a3dff71c1c88 ("lkdtm: split usercopy tests to separate file")
Acked-by: Kees Cook <[email protected]> I thought I already sent this fix to Greg? Maybe it got lost... -Kees > --- > 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 > -- Kees Cook Chrome OS & Brillo Security
