From: Michal Hocko <mhocko@kernel.org>
To: Brian Norris <briannorris@chromium.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>,
Andy Lutomirski <luto@kernel.org>,
Phil not Paul Oester <kernel@linuxace.com>,
linux-kernel@vger.kernel.org, stable@vger.kernel.org,
Willy Tarreau <w@1wt.eu>, Guenter Roeck <linux@roeck-us.net>,
Kees Cook <keescook@chromium.org>,
Dmitry Torokhov <dmitry.torokhov@gmail.com>
Subject: Re: [3.8 Regression] backporting "[PATCH stable pre 3.9] mm, gup: close FOLL MAP_PRIVATE race"
Date: Fri, 21 Oct 2016 08:46:02 +0200 [thread overview]
Message-ID: <20161021064602.GD6045@dhcp22.suse.cz> (raw)
In-Reply-To: <20161021063938.GA5463@google.com>
On Thu 20-10-16 23:39:39, Brian Norris wrote:
> (Preface: this wasn't a clean backport, I'm a bit under the weather, and
> it's getting late here. So forgive me if my head's not on straight.)
>
> Hi,
>
> I'm not sure the best way to report this, but the Chrome OS test
> infrastructure noticed some problems when testing the following patch
> backported to our 3.8 kernels:
>
> http://www.spinics.net/lists/stable/msg147998.html
>
> Specifically (if you can hold your nose and stand Gerrit), this change:
>
> https://chromium-review.googlesource.com/#/c/401041/
This is not correct. You have
https://chromium-review.googlesource.com/#/c/401041/2/mm/memory.c
f ((flags & FOLL_WRITE) && !can_follow_write_pte(pte, page, flags)) {
pte_unmap_unlock(ptep, ptl);
goto no_page;
}
so you do a double unlock. See how my patch does
+ if ((flags & FOLL_WRITE) && !can_follow_write_pte(pte, page, flags)) {
+ pte_unmap_unlock(ptep, ptl);
+ return NULL;
+ }
--
Michal Hocko
SUSE Labs
next prev parent reply other threads:[~2016-10-21 6:46 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-10-21 6:39 [3.8 Regression] backporting "[PATCH stable pre 3.9] mm, gup: close FOLL MAP_PRIVATE race" Brian Norris
2016-10-21 6:46 ` Michal Hocko [this message]
2016-10-21 16:53 ` Brian Norris
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