linux-kernel - Re: [kernel-hardening] [PATCH 09/38] usercopy: Mark kmalloc caches as usercopy caches

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Message-Id: <5861936c-1fe1-4c44-d012-26efa0c8b6e7@de.ibm.com>
Date:   Tue, 28 Jan 2020 08:58:31 +0100
From:   Christian Borntraeger <borntraeger@...ibm.com>
To:     Kees Cook <keescook@...omium.org>, Jiri Slaby <jslaby@...e.cz>,
        Julian Wiedmann <jwi@...ux.ibm.com>,
        Ursula Braun <ubraun@...ux.ibm.com>
Cc:     Alexander Viro <viro@...iv.linux.org.uk>,
        linux-kernel@...r.kernel.org, David Windsor <dave@...lcore.net>,
        Pekka Enberg <penberg@...nel.org>,
        David Rientjes <rientjes@...gle.com>,
        Joonsoo Kim <iamjoonsoo.kim@....com>,
        Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
        linux-xfs@...r.kernel.org,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Andy Lutomirski <luto@...nel.org>,
        Christoph Hellwig <hch@...radead.org>,
        Christoph Lameter <cl@...ux.com>,
        "David S. Miller" <davem@...emloft.net>,
        Laura Abbott <labbott@...hat.com>,
        Mark Rutland <mark.rutland@....com>,
        "Martin K. Petersen" <martin.petersen@...cle.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Christoffer Dall <christoffer.dall@...aro.org>,
        Dave Kleikamp <dave.kleikamp@...cle.com>,
        Jan Kara <jack@...e.cz>,
        Luis de Bethencourt <luisbg@...nel.org>,
        Marc Zyngier <marc.zyngier@....com>,
        Rik van Riel <riel@...hat.com>,
        Matthew Garrett <mjg59@...gle.com>,
        linux-fsdevel@...r.kernel.org, linux-arch@...r.kernel.org,
        netdev@...r.kernel.org, kernel-hardening@...ts.openwall.com,
        Vlastimil Babka <vbabka@...e.cz>,
        Michal Kubecek <mkubecek@...e.cz>
Subject: Re: [kernel-hardening] [PATCH 09/38] usercopy: Mark kmalloc caches as
 usercopy caches



On 28.01.20 00:19, Kees Cook wrote:
> On Thu, Jan 23, 2020 at 09:14:20AM +0100, Jiri Slaby wrote:
>> On 14. 11. 19, 22:27, Kees Cook wrote:
>>> On Tue, Nov 12, 2019 at 01:21:54PM -0800, Kees Cook wrote:
>>>> How is iucv the only network protocol that has run into this? Do others
>>>> use a bounce buffer?
>>>
>>> Another solution would be to use a dedicated kmem cache (instead of the
>>> shared kmalloc dma one)?
>>
>> Has there been any conclusion to this thread yet? For the time being, we
>> disabled HARDENED_USERCOPY on s390...
>>
>> https://lore.kernel.org/kernel-hardening/9519edb7-456a-a2fa-659e-3e5a1ff89466@suse.cz/
> 
> I haven't heard anything new. What did people think of a separate kmem
> cache?
> 

Adding Julian and Ursula. A separate kmem cache for iucv might be indeed
a solution for the user hardening issue.
On the other hand not marking the DMA caches still seems questionable.

For reference
https://bugzilla.suse.com/show_bug.cgi?id=1156053
the kernel hardening now triggers a warning.