linux-kernel - Re: [PATCH] x86/mm/64: Fix crash in remove

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:   Tue, 25 Apr 2017 12:01:22 -0700
From:   Dan Williams <dan.j.williams@...el.com>
To:     Ingo Molnar <mingo@...nel.org>
Cc:     "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        X86 ML <x86@...nel.org>, Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>, Andi Kleen <ak@...ux.intel.com>,
        Dave Hansen <dave.hansen@...el.com>,
        Andy Lutomirski <luto@...capital.net>,
        Linux MM <linux-mm@...ck.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] x86/mm/64: Fix crash in remove_pagetable()

On Tue, Apr 25, 2017 at 11:53 AM, Ingo Molnar <mingo@...nel.org> wrote:
>
> * Dan Williams <dan.j.williams@...el.com> wrote:
>
>> On Tue, Apr 25, 2017 at 2:25 AM, Kirill A. Shutemov
>> <kirill.shutemov@...ux.intel.com> 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 <kirill.shutemov@...ux.intel.com>
>> > Reported-by: Dan Williams <dan.j.williams@...el.com>
>> > 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 <dan.j.williams@...el.com>
>
> 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