Silent stack-heap collision under GNU/Linux

[Ian Lance Taylor]

On Sun, Jul 20, 2014 at 10:49 AM, Vincent Lefevre
<vincent+gcc@vinc17.org> wrote:
> It appears that GCC can generate code that yields silent stack-heap
> collision under GNU/Linux. I mean, the program doesn't crash (at least
> not immediately), the memory just gets corrupted. At the same time,
> this overrides the stack-size limit defined at the kernel level
> (getrlimit system call / RLIMIT_STACK) because the kernel has no
> chance to detect the collision (no page fault); thus this limit
> doesn't protect the user, and the problem seems to be on GCC's side.
>
> Why aren't such collisions detected by default?

Because it's expensive, and GCC takes the attitude that the C language
comes without safety guards.


> How can one tell GCC to detect them?

Use the -fstack-check option.  Or -fsanitize=address.  Or if you don't
need variable length arrays at all, you could use -Werror=vla.

Ian