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

[陈力恒]

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?)


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 "