From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-oi0-f71.google.com (mail-oi0-f71.google.com [209.85.218.71]) by kanga.kvack.org (Postfix) with ESMTP id 41CD06B02F2 for ; Tue, 25 Apr 2017 15:01:25 -0400 (EDT) Received: by mail-oi0-f71.google.com with SMTP id k77so106242661oih.11 for ; Tue, 25 Apr 2017 12:01:25 -0700 (PDT) Received: from mail-oi0-x236.google.com (mail-oi0-x236.google.com. [2607:f8b0:4003:c06::236]) by mx.google.com with ESMTPS id 126si13212114oig.267.2017.04.25.12.01.23 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 25 Apr 2017 12:01:23 -0700 (PDT) Received: by mail-oi0-x236.google.com with SMTP id y11so151100050oie.0 for ; Tue, 25 Apr 2017 12:01:23 -0700 (PDT) MIME-Version: 1.0 In-Reply-To: <20170425185333.3ecz46gn5ufy4bwi@gmail.com> References: <20170425092557.21852-1-kirill.shutemov@linux.intel.com> <20170425185333.3ecz46gn5ufy4bwi@gmail.com> From: Dan Williams Date: Tue, 25 Apr 2017 12:01:22 -0700 Message-ID: Subject: Re: [PATCH] x86/mm/64: Fix crash in remove_pagetable() Content-Type: text/plain; charset=UTF-8 Sender: owner-linux-mm@kvack.org List-ID: To: Ingo Molnar Cc: "Kirill A. Shutemov" , X86 ML , Thomas Gleixner , Ingo Molnar , "H. Peter Anvin" , Andi Kleen , Dave Hansen , Andy Lutomirski , Linux MM , "linux-kernel@vger.kernel.org" On Tue, Apr 25, 2017 at 11:53 AM, Ingo Molnar wrote: > > * Dan Williams wrote: > >> On Tue, Apr 25, 2017 at 2:25 AM, Kirill A. Shutemov >> wrote: >> > remove_pagetable() does page walk using p*d_page_vaddr() plus cast. >> > It's not canonical approach -- we usually use p*d_offset() for that. >> > >> > It works fine as long as all page table levels are present. We broke the >> > invariant by introducing folded p4d page table level. >> > >> > As result, remove_pagetable() interprets PMD as PUD and it leads to >> > crash: >> > >> > BUG: unable to handle kernel paging request at ffff880300000000 >> > IP: memchr_inv+0x60/0x110 >> > PGD 317d067 >> > P4D 317d067 >> > PUD 3180067 >> > PMD 33f102067 >> > PTE 8000000300000060 >> > >> > Let's fix this by using p*d_offset() instead of p*d_page_vaddr() for >> > page walk. >> > >> > Signed-off-by: Kirill A. Shutemov >> > Reported-by: Dan Williams >> > Fixes: f2a6a7050109 ("x86: Convert the rest of the code to support p4d_t") >> >> Thanks! This patch on top of tip/master passes a full run of the >> nvdimm regression suite. >> >> Tested-by: Dan Williams > > Does a re-application of: > > "x86/mm/gup: Switch GUP to the generic get_user_page_fast() implementation" > > still work (which you can achive via 'git revert 6dd29b3df975'), or is that > another breakage? That's another breakage. We're discussing how to resolve it in this thread: http://www.spinics.net/lists/linux-mm/msg126056.html -- 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