Re: [PATCH] Restrict stack space reservation to rlimit

[AmÃrico Wang]

On Mon, Feb 8, 2010 at 2:05 PM, KOSAKI Motohiro
<kosaki.motohiro@xxxxxxxxxxxxxx> wrote:
>> --- linux-2.6-ozlabs.orig/fs/exec.c
>> +++ linux-2.6-ozlabs/fs/exec.c
>> @@ -627,10 +627,13 @@ int setup_arg_pages(struct linux_binprm
>> Â Â Â Â Â Â Â Â Â Â Â goto out_unlock;
>> Â Â Â }
>>
>> + Â Â stack_base = min(EXTRA_STACK_VM_PAGES * PAGE_SIZE,
>> + Â Â Â Â Â Â Â Â Â Â Âcurrent->signal->rlim[RLIMIT_STACK].rlim_cur -
>> + Â Â Â Â Â Â Â Â Â Â Â ÂPAGE_SIZE);
>
> This line is a bit unclear why "- PAGE_SIZE" is necessary.
> personally, I like following likes explicit comments.
>
> Â Â Â Âstack_expand = EXTRA_STACK_VM_PAGES * PAGE_SIZE;
> Â Â Â Âstack_lim = ACCESS_ONCE(rlim[RLIMIT_STACK].rlim_cur);
>
> Â Â Â Â/* Initial stack must not cause stack overflow. */
> Â Â Â Âif (stack_expand + PAGE_SIZE > stack_lim)
> Â Â Â Â Â Â Â Âstack_expand = stack_lim - PAGE_SIZE;
>
> note: accessing rlim_cur require ACCESS_ONCE.
>
>
> Thought?

It's better to use the helper function: rlimit().
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/