From: Martin Schwidefsky <schwidefsky@de.ibm.com>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Christoph Hellwig <hch@infradead.org>,
linuxppc-dev@lists.ozlabs.org,
Linux List Kernel Mailing <linux-kernel@vger.kernel.org>,
linux-s390 <linux-s390@vger.kernel.org>
Subject: Re: Linux 5.1-rc5
Date: Tue, 16 Apr 2019 11:09:06 +0200 [thread overview]
Message-ID: <20190416110906.6c773aff@mschwideX1> (raw)
In-Reply-To: <CAHk-=wj7jgMOVFW0tiU-X+zhg6+Rn7mEBTej+f26rV3zXezOSA@mail.gmail.com>
On Mon, 15 Apr 2019 09:17:10 -0700
Linus Torvalds <torvalds@linux-foundation.org> wrote:
> On Sun, Apr 14, 2019 at 10:19 PM Christoph Hellwig <hch@infradead.org> wrote:
> >
> > Can we please have the page refcount overflow fixes out on the list
> > for review, even if it is after the fact?
>
> They were actually on a list for review long before the fact, but it
> was the security mailing list. The issue actually got discussed back
> in January along with early versions of the patches, but then we
> dropped the ball because it just wasn't on anybody's radar and it got
> resurrected late March. Willy wrote a rather bigger patch-series, and
> review of that is what then resulted in those commits. So they may
> look recent, but that's just because the original patches got
> seriously edited down and rewritten.
First time I hear about this, thanks for the heads up.
> That said, powerpc and s390 should at least look at maybe adding a
> check for the page ref in their gup paths too. Powerpc has the special
> gup_hugepte() case, and s390 has its own version of gup entirely. I
> was actually hoping the s390 guys would look at using the generic gup
> code.
We did look at converting the s390 gup code to CONFIG_HAVE_GENERIC_GUP,
there are some details that need careful consideration. The top one
is access_ok(), for s390 we always return true. The generic gup code
relies on the fact that a page table walk with a specific address is
doable if access_ok() returned true, the s390 specific check is slightly
different:
if ((end <= start) || (end > mm->context.asce_limit))
return 0;
The obvious approach would be to modify access_ok() to check against
the asce_limit. I will try and see if anything breaks, e.g. the automatic
page table upgrade.
> I ruthlessly also entirely ignored MIPS, SH and sparc, since they seem
> largely irrelevant, partly since even theoretically this whole issue
> needs a _lot_ of memory.
>
> Michael, Martin, see commit 6b3a70773630 ("Merge branch 'page-refs'
> (page ref overflow)"). You may or may not really care.
On s390 we can have up to 16TB of memory in a single LPAR. So yes, I do
care about it.
--
blue skies,
Martin.
"Reality continues to ruin my life." - Calvin.
next prev parent reply other threads:[~2019-04-16 9:11 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <CAHk-=wjvcuyCQGnfOhooaL1H4H63qXO=xgo+9yncSOG=eK+kbA@mail.gmail.com>
[not found] ` <20190415051919.GA31481@infradead.org>
2019-04-15 16:17 ` Linux 5.1-rc5 Linus Torvalds
2019-04-16 9:09 ` Martin Schwidefsky [this message]
2019-04-16 12:06 ` Martin Schwidefsky
2019-04-16 16:16 ` Linus Torvalds
2019-04-16 16:49 ` Linus Torvalds
2019-04-17 7:46 ` Martin Schwidefsky
2019-04-17 8:02 ` Martin Schwidefsky
2019-04-17 16:57 ` Linus Torvalds
2019-04-18 8:02 ` Martin Schwidefsky
2019-04-18 15:49 ` Linus Torvalds
2019-04-18 18:41 ` Martin Schwidefsky
2019-04-19 13:33 ` Martin Schwidefsky
2019-04-19 17:27 ` Linus Torvalds
2019-04-23 15:38 ` Martin Schwidefsky
2019-04-23 16:06 ` Linus Torvalds
2019-04-17 3:38 ` Michael Ellerman
2019-04-17 4:13 ` Linus Torvalds
2019-05-02 12:21 ` Greg KH
2019-05-02 14:17 ` Martin Schwidefsky
2019-05-02 14:31 ` Greg KH
2019-05-02 15:10 ` Martin Schwidefsky
2019-05-20 11:09 ` Greg KH
2019-05-03 13:31 ` Michael Ellerman
2019-05-02 23:15 ` Christoph Hellwig
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