linux-kernel - Re: [PATCHv3 5/8] x86/uaccess: Provide untagged_addr() and remove tags before address check

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]

Message-ID: <CAMe9rOq_WT-dxS3xthGtagn=aHruHyUJDR_=RDvMi9vX5PCmnA@mail.gmail.com>
Date:   Fri, 17 Jun 2022 07:22:57 -0700
From:   "H.J. Lu" <hjl.tools@...il.com>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        "Edgecombe, Rick P" <rick.p.edgecombe@...el.com>,
        "Lutomirski, Andy" <luto@...nel.org>,
        "dave.hansen@...ux.intel.com" <dave.hansen@...ux.intel.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        "kcc@...gle.com" <kcc@...gle.com>,
        "andreyknvl@...il.com" <andreyknvl@...il.com>,
        "ak@...ux.intel.com" <ak@...ux.intel.com>,
        "dvyukov@...gle.com" <dvyukov@...gle.com>,
        "x86@...nel.org" <x86@...nel.org>,
        "ryabinin.a.a@...il.com" <ryabinin.a.a@...il.com>,
        "glider@...gle.com" <glider@...gle.com>
Subject: Re: [PATCHv3 5/8] x86/uaccess: Provide untagged_addr() and remove
 tags before address check

On Fri, Jun 17, 2022 at 4:36 AM Peter Zijlstra <peterz@...radead.org> wrote:
>
> On Thu, Jun 16, 2022 at 07:44:40PM +0300, Kirill A. Shutemov wrote:
> > Any objection against this variant (was posted in the thread):
> >
> >               #define untagged_addr(mm, addr) ({                                      \
> >                       u64 __addr = (__force u64)(addr);                               \
> >                       s64 sign = (s64)__addr >> 63;                                   \
> >                       __addr &= (mm)->context.untag_mask | sign;                      \
> >                       (__force __typeof__(addr))__addr;                               \
> >               })
> >
> > ?
>
> Yeah, I suppose that should work fine.

Won't the sign bit be put at the wrong place?

-- 
H.J.