linux-kernel - Re: [PATCH 0/4] arch, mm: improve robustness of direct map manipulation

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: <20201026090526.GA1154158@kernel.org>
Date:   Mon, 26 Oct 2020 11:05:26 +0200
From:   Mike Rapoport <rppt@...nel.org>
To:     "Edgecombe, Rick P" <rick.p.edgecombe@...el.com>
Cc:     "akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
        "david@...hat.com" <david@...hat.com>,
        "cl@...ux.com" <cl@...ux.com>,
        "gor@...ux.ibm.com" <gor@...ux.ibm.com>,
        "hpa@...or.com" <hpa@...or.com>,
        "peterz@...radead.org" <peterz@...radead.org>,
        "catalin.marinas@....com" <catalin.marinas@....com>,
        "dave.hansen@...ux.intel.com" <dave.hansen@...ux.intel.com>,
        "borntraeger@...ibm.com" <borntraeger@...ibm.com>,
        "will@...nel.org" <will@...nel.org>,
        "penberg@...nel.org" <penberg@...nel.org>,
        "iamjoonsoo.kim@....com" <iamjoonsoo.kim@....com>,
        "aou@...s.berkeley.edu" <aou@...s.berkeley.edu>,
        "kirill@...temov.name" <kirill@...temov.name>,
        "rientjes@...gle.com" <rientjes@...gle.com>,
        "rppt@...ux.ibm.com" <rppt@...ux.ibm.com>,
        "paulus@...ba.org" <paulus@...ba.org>,
        "hca@...ux.ibm.com" <hca@...ux.ibm.com>,
        "pavel@....cz" <pavel@....cz>, "bp@...en8.de" <bp@...en8.de>,
        "sparclinux@...r.kernel.org" <sparclinux@...r.kernel.org>,
        "mpe@...erman.id.au" <mpe@...erman.id.au>,
        "luto@...nel.org" <luto@...nel.org>,
        "davem@...emloft.net" <davem@...emloft.net>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        "tglx@...utronix.de" <tglx@...utronix.de>,
        "rjw@...ysocki.net" <rjw@...ysocki.net>,
        "linux-riscv@...ts.infradead.org" <linux-riscv@...ts.infradead.org>,
        "benh@...nel.crashing.org" <benh@...nel.crashing.org>,
        "linuxppc-dev@...ts.ozlabs.org" <linuxppc-dev@...ts.ozlabs.org>,
        "x86@...nel.org" <x86@...nel.org>,
        "linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "palmer@...belt.com" <palmer@...belt.com>,
        "Brown, Len" <len.brown@...el.com>,
        "mingo@...hat.com" <mingo@...hat.com>,
        "linux-s390@...r.kernel.org" <linux-s390@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "paul.walmsley@...ive.com" <paul.walmsley@...ive.com>
Subject: Re: [PATCH 0/4] arch, mm: improve robustness of direct map
 manipulation

On Mon, Oct 26, 2020 at 01:13:52AM +0000, Edgecombe, Rick P wrote:
> On Sun, 2020-10-25 at 12:15 +0200, Mike Rapoport wrote:
> > Indeed, for architectures that define CONFIG_ARCH_HAS_SET_DIRECT_MAP
> > it is
> > possible that __kernel_map_pages() would fail, but since this
> > function is
> > void, the failure will go unnoticed.
> 
> Could you elaborate on how this could happen? Do you mean during
> runtime today or if something new was introduced?

A failure in__kernel_map_pages() may happen today. For instance, on x86
if the kernel is built with DEBUG_PAGEALLOC.

	__kernel_map_pages(page, 1, 0);

will need to split, say, 2M page and during the split an allocation of
page table could fail.

Currently, the only user of __kernel_map_pages() outside DEBUG_PAGEALLOC
is hibernation, but I think it would be safer to entirely prevent usage
of __kernel_map_pages() when DEBUG_PAGEALLOC=n.

-- 
Sincerely yours,
Mike.