[LTP] [PATCH] sigaltstack01: Fix check about alternative stack

[Petr Vorel]

Hi Liheng Chen,

> Hi Petr Vorel,


> Recently I want to test if Gramine-SGX (emulates Linux in Intel SGX trusted execution environment) works exactly like Linux, and avoid it from harming users.


> sigaltstack01 mallocs a buffer with size SIGSTKSZ (8192) and uses this buffer as an alternative stack. However, in Gramine-SGX, it needs to reserve a large memory to save xstate, sigframe, and restorer's address, thus it needs to reserve memory larger than 11452 bytes, which overflows SIGSTKSZ. In this situation, I noticed the wrong check we talked about. (Detail: https://github.com/gramineproject/gramine/issues/2153 , is it OK to paste a link?)

Thanks a lot for sharing the details and your patch!
Merged with added additional info from you to the commit message.

Kind regards,
Petr

> Kind regards,
> Liheng Chen


> ------------------ Original ------------------


> Hi Liheng,

> > Hi all,

> > This check seems should be (alt_stk < sigstk.ss_sp) || (alt_stk > (sigstk.ss_sp + SIGSTKSZ)), not &&

> You're right. IMHO the error goes down to the original addition in
> 865695bbc89088b9526ea9045410e5afb70a985c

> Out of curiosity, did you find a system where it should fail but it didn't?

> Reviewed-by: Petr Vorel <pvorel@suse.cz>

> > Kind regards,
> > Liheng Chen

> > Signed-off-by: Liheng Chen <791960492@qq.com>
> > ---
> >  testcases/kernel/syscalls/sigaltstack/sigaltstack01.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)

> > diff --git a/testcases/kernel/syscalls/sigaltstack/sigaltstack01.c b/testcases/kernel/syscalls/sigaltstack/sigaltstack01.c
> > index 9a2e3a440..147659467 100644
> > --- a/testcases/kernel/syscalls/sigaltstack/sigaltstack01.c
> > +++ b/testcases/kernel/syscalls/sigaltstack/sigaltstack01.c
> > @@ -142,7 +142,7 @@ int main(int ac, char **av)
> >  			 * Check that main_stk is outside the
> >  			 * alternate stk boundaries.
> >  			 */
> > -			if ((alt_stk < sigstk.ss_sp) &&
> > +			if ((alt_stk < sigstk.ss_sp) ||
> >  			    (alt_stk > (sigstk.ss_sp + SIGSTKSZ))) {
> >  				tst_resm(TFAIL,
> >  					 "alt. stack is not within the "