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: Fri, 14 Feb 2020 16:07:04 -0500 [thread overview]
Message-ID: <x497e0odgjr.fsf@segfault.boston.devel.redhat.com> (raw)
In-Reply-To: <20200213121416.57ddim2ygktctjrl@box> (Kirill A. Shutemov's message of "Thu, 13 Feb 2020 15:14:16 +0300")
"Kirill A. Shutemov" <kirill@shutemov.name> writes:
> On Wed, Feb 12, 2020 at 09:22:03AM -0500, Jeff Moyer wrote:
>> "Kirill A. Shutemov" <kirill@shutemov.name> writes:
>>
>> > On Tue, Feb 11, 2020 at 11:27:36AM -0500, Jeff Moyer wrote:
>> >> > 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. :)
>> >
>> > The first attempt on the real solution is below.
>> >
>> > Yeah, this is ugly. Any suggestion on clearing up this mess is welcome.
>> >
>> > Jeff, could you give it a try?
>>
>> Yes, that patch appears to fix the problem. I wonder if we could remove
>> the clear_page completely, though. I'd rather see the program segfault
>> than operate on bad data. What do you think?
>
> It is long standing policy: see 6aab341e0a28 ("mm: re-architect the
> VM_UNPAGED logic") from 2005. Some obscure case may break if change it.
I'll take your word for it.
> I think it is fine to live with the WARN for a while and change it to
> SIGBUS once we can be relatively sure that it is okay.
OK, fine by me.
Thanks for looking into this!
-Jeff
prev parent reply other threads:[~2020-02-14 21:07 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
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 [this message]
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=x497e0odgjr.fsf@segfault.boston.devel.redhat.com \
--to=jmoyer@redhat.com \
--cc=catalin.marinas@arm.com \
--cc=justin.he@arm.com \
--cc=kirill.shutemov@linux.intel.com \
--cc=kirill@shutemov.name \
--cc=linux-mm@kvack.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).