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From: Jeff Moyer <jmoyer@redhat.com>
To: "Kirill A. Shutemov" <kirill@shutemov.name>
Cc: Jia He <justin.he@arm.com>,
	 Catalin Marinas <catalin.marinas@arm.com>,
	 "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
	 linux-mm@kvack.org
Subject: Re: bug: data corruption introduced by commit 83d116c53058 ("mm: fix double page fault on arm64 if PTE_AF is cleared")
Date: Tue, 11 Feb 2020 11:27:36 -0500	[thread overview]
Message-ID: <x49wo8tnl6v.fsf@segfault.boston.devel.redhat.com> (raw)
In-Reply-To: <20200211145158.5wt7nepe3flx25bj@box> (Kirill A. Shutemov's message of "Tue, 11 Feb 2020 17:51:58 +0300")

Hi, Kirill,

"Kirill A. Shutemov" <kirill@shutemov.name> writes:

> My guess is that MADV_DONTNEED get the page unmapped under you and
> __copy_from_user_inatomic() sees empty PTE instead of the populated PTE it
> expects.
>
> Below is my completely untested attempt to fix it.
>
> It is going to hurt perfomance in common case, but it should be good
> enough to test my idea.

Yes, that resolves the issue for me.

> The real solution would be to retry __copy_from_user_inatomic() under ptl
> if the first attempt fails. I expect it to be ugly.

So long as it's correct.  :)

Thanks!
Jeff



  reply	other threads:[~2020-02-11 16:27 UTC|newest]

Thread overview: 15+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-02-10 22:51 bug: data corruption introduced by commit 83d116c53058 ("mm: fix double page fault on arm64 if PTE_AF is cleared") Jeff Moyer
2020-02-11  4:17 ` Justin He
2020-02-11  4:29   ` Justin He
2020-02-11 16:44     ` Jeff Moyer
2020-02-11 17:33       ` Kirill A. Shutemov
2020-02-11 17:55         ` Jeff Moyer
2020-02-11 21:44           ` Kirill A. Shutemov
2020-02-11 22:01             ` Jeff Moyer
2020-02-11 22:15               ` Kirill A. Shutemov
2020-02-11 14:51 ` Kirill A. Shutemov
2020-02-11 16:27   ` Jeff Moyer [this message]
2020-02-11 22:40     ` Kirill A. Shutemov
2020-02-12 14:22       ` Jeff Moyer
2020-02-13 12:14         ` Kirill A. Shutemov
2020-02-14 21:07           ` Jeff Moyer

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