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

From	Oleg Nesterov <oleg@redhat.com>
Newsgroups	linux.kernel
Subject	Re: [PATCHv3 01/12] uprobes: split THPs before trying replace them
Date	2017-01-31 17:10 +0100
Message-ID	<t5Jai-2Mv-5@gated-at.bofh.it> (permalink)
References	<t51Ci-1v9-13@gated-at.bofh.it> <t51Ci-1v9-11@gated-at.bofh.it>
Organization	linux.* mail to news gateway

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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@redhat.com>

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Re: [PATCHv3 01/12] uprobes: split THPs before trying replace them Oleg Nesterov <oleg@redhat.com> - 2017-01-31 17:10 +0100

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