Re: [PATCH] ELF: warn if process starts with executable stack

[Andrew Morton]

On Mon, 18 Nov 2019 17:51:15 +0300 Alexey Dobriyan <adobriyan@xxxxxxxxx> wrote:

> PT_GNU_STACK is fail open design,

Not sure what this means.  Please expand on the motivation for this
change.

> at least warn people that something
> isn't right.

People who use an executable stack get a kernel splat.  How is that
useful?

> ...
>
> --- a/fs/exec.c
> +++ b/fs/exec.c
> @@ -762,6 +762,13 @@ int setup_arg_pages(struct linux_binprm *bprm,
>  		goto out_unlock;
>  	BUG_ON(prev != vma);
>  
> +#ifdef CONFIG_MMU
> +	if (vm_flags & VM_EXEC) {
> +		pr_warn_once("process '%s'/%u started with executable stack\n",
> +			     current->comm, current->pid);
> +	}
> +#endif
>
>  	/* Move stack pages down in memory. */
>  	if (stack_shift) {
>  		ret = shift_arg_pages(vma, stack_shift);