From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pa0-f51.google.com (mail-pa0-f51.google.com [209.85.220.51]) by kanga.kvack.org (Postfix) with ESMTP id B0ACC6B0253 for ; Tue, 13 Oct 2015 01:53:12 -0400 (EDT) Received: by padhy16 with SMTP id hy16so10569045pad.1 for ; Mon, 12 Oct 2015 22:53:12 -0700 (PDT) Received: from mail.linuxfoundation.org (mail.linuxfoundation.org. [140.211.169.12]) by mx.google.com with ESMTPS id yw10si2494582pac.86.2015.10.12.22.53.11 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 12 Oct 2015 22:53:11 -0700 (PDT) Date: Mon, 12 Oct 2015 22:41:24 -0700 From: Greg Kroah-Hartman Subject: Re: [PATCH v2] thp: use is_zero_pfn only after pte_present check Message-ID: <20151013054124.GB20952@kroah.com> References: <1444703918-16597-1-git-send-email-minchan@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1444703918-16597-1-git-send-email-minchan@kernel.org> Sender: owner-linux-mm@kvack.org List-ID: To: Minchan Kim Cc: Andrew Morton , "Kirill A. Shutemov" , Mel Gorman , Vlastimil Babka , Andrea Arcangeli , Hugh Dickins , Rik van Riel , linux-kernel@vger.kernel.org, linux-mm@kvack.org, stable@vger.kernel.org, "Kirill A. Shutemov" On Tue, Oct 13, 2015 at 11:38:38AM +0900, Minchan Kim wrote: > Use is_zero_pfn on pteval only after pte_present check on pteval > (It might be better idea to introduce is_zero_pte where checks > pte_present first). Otherwise, it could work with swap or > migration entry and if pte_pfn's result is equal to zero_pfn > by chance, we lose user's data in __collapse_huge_page_copy. > So if you're luck, the application is segfaulted and finally you > could see below message when the application is exit. > > BUG: Bad rss-counter state mm:ffff88007f099300 idx:2 val:3 > > Cc: > Acked-by: Kirill A. Shutemov > Reviewed-by: Andrea Arcangeli > Signed-off-by: Minchan Kim > --- > Hello Greg, > > This patch should go to -stable but when you will apply it > after merging of linus tree, it will be surely conflicted due > to userfaultfd part. > > I want to know how to handle it. You will get an automated email saying it didn't apply and then you provide a backported version. Or you send a properly backported version to stable@vger.kernel.org before then, with the git commit id of the patch in Linus's tree. thanks, greg k-h -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org