Re: [PATCHv3 01/12] uprobes: split THPs before trying replace them

[Oleg Nesterov]

On 01/29, Kirill A. Shutemov wrote:
>
> For THPs page_check_address() always fails. It leads to endless loop in
> uprobe_write_opcode().
>
> Testcase with huge-tmpfs (not sure if it's possible to trigger this
> uprobe codepath for anon memory):

No, you can't probe the anonymous memory,

> --- a/kernel/events/uprobes.c
> +++ b/kernel/events/uprobes.c
> @@ -300,8 +300,8 @@ int uprobe_write_opcode(struct mm_struct *mm, unsigned long vaddr,
>  
>  retry:
>  	/* Read the page with vaddr into memory */
> -	ret = get_user_pages_remote(NULL, mm, vaddr, 1, FOLL_FORCE, &old_page,
> -			&vma, NULL);
> +	ret = get_user_pages_remote(NULL, mm, vaddr, 1,
> +			FOLL_FORCE | FOLL_SPLIT, &old_page, &vma, NULL);
>  	if (ret <= 0)
>  		return ret;

Thanks,

Acked-by: Oleg Nesterov <oleg@xxxxxxxxxx>