Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
Subject: Re: [kernel-hardening] [PATCH 09/38] usercopy: Mark kmalloc caches as
 usercopy caches
To:     Vlastimil Babka <vbabka@suse.cz>, Jann Horn <jannh@google.com>,
        Kees Cook <keescook@chromium.org>
Cc:     Christoph Hellwig <hch@infradead.org>,
        Christopher Lameter <cl@linux.com>,
        Jiri Slaby <jslaby@suse.cz>,
        Julian Wiedmann <jwi@linux.ibm.com>,
        Ursula Braun <ubraun@linux.ibm.com>,
        Alexander Viro <viro@zeniv.linux.org.uk>,
        kernel list <linux-kernel@vger.kernel.org>,
        David Windsor <dave@nullcore.net>,
        Pekka Enberg <penberg@kernel.org>,
        David Rientjes <rientjes@google.com>,
        Joonsoo Kim <iamjoonsoo.kim@lge.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Linux-MM <linux-mm@kvack.org>, linux-xfs@vger.kernel.org,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Andy Lutomirski <luto@kernel.org>,
        "David S. Miller" <davem@davemloft.net>,
        Laura Abbott <labbott@redhat.com>,
        Mark Rutland <mark.rutland@arm.com>,
        "Martin K. Petersen" <martin.petersen@oracle.com>,
        Paolo Bonzini <pbonzini@redhat.com>,
        Christoffer Dall <christoffer.dall@linaro.org>,
        Dave Kleikamp <dave.kleikamp@oracle.com>,
        Jan Kara <jack@suse.cz>,
        Luis de Bethencourt <luisbg@kernel.org>,
        Marc Zyngier <marc.zyngier@arm.com>,
        Rik van Riel <riel@redhat.com>,
        Matthew Garrett <mjg59@google.com>,
        linux-fsdevel <linux-fsdevel@vger.kernel.org>,
        linux-arch <linux-arch@vger.kernel.org>,
        Network Development <netdev@vger.kernel.org>,
        Kernel Hardening <kernel-hardening@lists.openwall.com>,
        Michal Kubecek <mkubecek@suse.cz>
References: <201911121313.1097D6EE@keescook> <201911141327.4DE6510@keescook>
 <bfca96db-bbd0-d958-7732-76e36c667c68@suse.cz>
 <202001271519.AA6ADEACF0@keescook>
 <5861936c-1fe1-4c44-d012-26efa0c8b6e7@de.ibm.com>
 <202001281457.FA11CC313A@keescook>
 <alpine.DEB.2.21.2001291640350.1546@www.lameter.com>
 <6844ea47-8e0e-4fb7-d86f-68046995a749@de.ibm.com>
 <20200129170939.GA4277@infradead.org>
 <771c5511-c5ab-3dd1-d938-5dbc40396daa@de.ibm.com>
 <202001300945.7D465B5F5@keescook>
 <CAG48ez1a4waGk9kB0WLaSbs4muSoK0AYAVk8=XYaKj4_+6e6Hg@mail.gmail.com>
 <7d810f6d-8085-ea2f-7805-47ba3842dc50@suse.cz>
From:   Christian Borntraeger <borntraeger@de.ibm.com>
Autocrypt: addr=borntraeger@de.ibm.com; prefer-encrypt=mutual; keydata=
 xsFNBE6cPPgBEAC2VpALY0UJjGmgAmavkL/iAdqul2/F9ONz42K6NrwmT+SI9CylKHIX+fdf
 J34pLNJDmDVEdeb+brtpwC9JEZOLVE0nb+SR83CsAINJYKG3V1b3Kfs0hydseYKsBYqJTN2j
 CmUXDYq9J7uOyQQ7TNVoQejmpp5ifR4EzwIFfmYDekxRVZDJygD0wL/EzUr8Je3/j548NLyL
 4Uhv6CIPf3TY3/aLVKXdxz/ntbLgMcfZsDoHgDk3lY3r1iwbWwEM2+eYRdSZaR4VD+JRD7p8
 0FBadNwWnBce1fmQp3EklodGi5y7TNZ/CKdJ+jRPAAnw7SINhSd7PhJMruDAJaUlbYaIm23A
 +82g+IGe4z9tRGQ9TAflezVMhT5J3ccu6cpIjjvwDlbxucSmtVi5VtPAMTLmfjYp7VY2Tgr+
 T92v7+V96jAfE3Zy2nq52e8RDdUo/F6faxcumdl+aLhhKLXgrozpoe2nL0Nyc2uqFjkjwXXI
 OBQiaqGeWtxeKJP+O8MIpjyGuHUGzvjNx5S/592TQO3phpT5IFWfMgbu4OreZ9yekDhf7Cvn
 /fkYsiLDz9W6Clihd/xlpm79+jlhm4E3xBPiQOPCZowmHjx57mXVAypOP2Eu+i2nyQrkapaY
 IdisDQfWPdNeHNOiPnPS3+GhVlPcqSJAIWnuO7Ofw1ZVOyg/jwARAQABzUNDaHJpc3RpYW4g
 Qm9ybnRyYWVnZXIgKDJuZCBJQk0gYWRkcmVzcykgPGJvcm50cmFlZ2VyQGxpbnV4LmlibS5j
 b20+wsF5BBMBAgAjBQJdP/hMAhsDBwsJCAcDAgEGFQgCCQoLBBYCAwECHgECF4AACgkQEXu8
 gLWmHHy/pA/+JHjpEnd01A0CCyfVnb5fmcOlQ0LdmoKWLWPvU840q65HycCBFTt6V62cDljB
 kXFFxMNA4y/2wqU0H5/CiL963y3gWIiJsZa4ent+KrHl5GK1nIgbbesfJyA7JqlB0w/E/SuY
 NRQwIWOo/uEvOgXnk/7+rtvBzNaPGoGiiV1LZzeaxBVWrqLtmdi1iulW/0X/AlQPuF9dD1Px
 hx+0mPjZ8ClLpdSp5d0yfpwgHtM1B7KMuQPQZGFKMXXTUd3ceBUGGczsgIMipZWJukqMJiJj
 QIMH0IN7XYErEnhf0GCxJ3xAn/J7iFpPFv8sFZTvukntJXSUssONnwiKuld6ttUaFhSuSoQg
 OFYR5v7pOfinM0FcScPKTkrRsB5iUvpdthLq5qgwdQjmyINt3cb+5aSvBX2nNN135oGOtlb5
 tf4dh00kUR8XFHRrFxXx4Dbaw4PKgV3QLIHKEENlqnthH5t0tahDygQPnSucuXbVQEcDZaL9
 WgJqlRAAj0pG8M6JNU5+2ftTFXoTcoIUbb0KTOibaO9zHVeGegwAvPLLNlKHiHXcgLX1tkjC
 DrvE2Z0e2/4q7wgZgn1kbvz7ZHQZB76OM2mjkFu7QNHlRJ2VXJA8tMXyTgBX6kq1cYMmd/Hl
 OhFrAU3QO1SjCsXA2CDk9MM1471mYB3CTXQuKzXckJnxHkHOwU0ETpw8+AEQAJjyNXvMQdJN
 t07BIPDtbAQk15FfB0hKuyZVs+0lsjPKBZCamAAexNRk11eVGXK/YrqwjChkk60rt3q5i42u
 PpNMO9aS8cLPOfVft89Y654Qd3Rs1WRFIQq9xLjdLfHh0i0jMq5Ty+aiddSXpZ7oU6E+ud+X
 Czs3k5RAnOdW6eV3+v10sUjEGiFNZwzN9Udd6PfKET0J70qjnpY3NuWn5Sp1ZEn6lkq2Zm+G
 9G3FlBRVClT30OWeiRHCYB6e6j1x1u/rSU4JiNYjPwSJA8EPKnt1s/Eeq37qXXvk+9DYiHdT
 PcOa3aNCSbIygD3jyjkg6EV9ZLHibE2R/PMMid9FrqhKh/cwcYn9FrT0FE48/2IBW5mfDpAd
 YvpawQlRz3XJr2rYZJwMUm1y+49+1ZmDclaF3s9dcz2JvuywNq78z/VsUfGz4Sbxy4ShpNpG
 REojRcz/xOK+FqNuBk+HoWKw6OxgRzfNleDvScVmbY6cQQZfGx/T7xlgZjl5Mu/2z+ofeoxb
 vWWM1YCJAT91GFvj29Wvm8OAPN/+SJj8LQazd9uGzVMTz6lFjVtH7YkeW/NZrP6znAwv5P1a
 DdQfiB5F63AX++NlTiyA+GD/ggfRl68LheSskOcxDwgI5TqmaKtX1/8RkrLpnzO3evzkfJb1
 D5qh3wM1t7PZ+JWTluSX8W25ABEBAAHCwV8EGAECAAkFAk6cPPgCGwwACgkQEXu8gLWmHHz8
 2w//VjRlX+tKF3szc0lQi4X0t+pf88uIsvR/a1GRZpppQbn1jgE44hgF559K6/yYemcvTR7r
 6Xt7cjWGS4wfaR0+pkWV+2dbw8Xi4DI07/fN00NoVEpYUUnOnupBgychtVpxkGqsplJZQpng
 v6fauZtyEcUK3dLJH3TdVQDLbUcL4qZpzHbsuUnTWsmNmG4Vi0NsEt1xyd/Wuw+0kM/oFEH1
 4BN6X9xZcG8GYUbVUd8+bmio8ao8m0tzo4pseDZFo4ncDmlFWU6hHnAVfkAs4tqA6/fl7RLN
 JuWBiOL/mP5B6HDQT9JsnaRdzqF73FnU2+WrZPjinHPLeE74istVgjbowvsgUqtzjPIG5pOj
 cAsKoR0M1womzJVRfYauWhYiW/KeECklci4TPBDNx7YhahSUlexfoftltJA8swRshNA/M90/
 i9zDo9ySSZHwsGxG06ZOH5/MzG6HpLja7g8NTgA0TD5YaFm/oOnsQVsf2DeAGPS2xNirmknD
 jaqYefx7yQ7FJXXETd2uVURiDeNEFhVZWb5CiBJM5c6qQMhmkS4VyT7/+raaEGgkEKEgHOWf
 ZDP8BHfXtszHqI3Fo1F4IKFo/AP8GOFFxMRgbvlAs8z/+rEEaQYjxYJqj08raw6P4LFBqozr
 nS4h0HDFPrrp1C2EMVYIQrMokWvlFZbCpsdYbBI=
Date:   Tue, 7 Apr 2020 13:05:46 +0200
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101
 Thunderbird/68.5.0
MIME-Version: 1.0
In-Reply-To: <7d810f6d-8085-ea2f-7805-47ba3842dc50@suse.cz>
Content-Type: text/plain; charset=utf-8
Content-Language: en-US
Content-Transfer-Encoding: 7bit
Message-Id: <aecba9ae-887d-39c5-c3b7-8236fbcaa898@de.ibm.com>
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk


On 07.04.20 10:00, Vlastimil Babka wrote:
> On 1/31/20 1:03 PM, Jann Horn wrote:
> 
>> I think dma-kmalloc slabs should be handled the same way as normal
>> kmalloc slabs. When a dma-kmalloc allocation is freshly created, it is
>> just normal kernel memory - even if it might later be used for DMA -,
>> and it should be perfectly fine to copy_from_user() into such
>> allocations at that point, and to copy_to_user() out of them at the
>> end. If you look at the places where such allocations are created, you
>> can see things like kmemdup(), memcpy() and so on - all normal
>> operations that shouldn't conceptually be different from usercopy in
>> any relevant way.
>  
> So, let's do that?
> 
> ----8<----
> From d5190e4e871689a530da3c3fd327be45a88f006a Mon Sep 17 00:00:00 2001
> From: Vlastimil Babka <vbabka@suse.cz>
> Date: Tue, 7 Apr 2020 09:58:00 +0200
> Subject: [PATCH] usercopy: Mark dma-kmalloc caches as usercopy caches
> 
> We have seen a "usercopy: Kernel memory overwrite attempt detected to SLUB
> object 'dma-kmalloc-1 k' (offset 0, size 11)!" error on s390x, as IUCV uses
> kmalloc() with __GFP_DMA because of memory address restrictions.
> The issue has been discussed [2] and it has been noted that if all the kmalloc
> caches are marked as usercopy, there's little reason not to mark dma-kmalloc
> caches too. The 'dma' part merely means that __GFP_DMA is used to restrict
> memory address range.
> 
> As Jann Horn put it [3]:
> 
> "I think dma-kmalloc slabs should be handled the same way as normal
> kmalloc slabs. When a dma-kmalloc allocation is freshly created, it is
> just normal kernel memory - even if it might later be used for DMA -,
> and it should be perfectly fine to copy_from_user() into such
> allocations at that point, and to copy_to_user() out of them at the
> end. If you look at the places where such allocations are created, you
> can see things like kmemdup(), memcpy() and so on - all normal
> operations that shouldn't conceptually be different from usercopy in
> any relevant way."
> 
> Thus this patch marks the dma-kmalloc-* caches as usercopy.
> 
> [1] https://bugzilla.suse.com/show_bug.cgi?id=1156053
> [2] https://lore.kernel.org/kernel-hardening/bfca96db-bbd0-d958-7732-76e36c667c68@suse.cz/
> [3] https://lore.kernel.org/kernel-hardening/CAG48ez1a4waGk9kB0WLaSbs4muSoK0AYAVk8=XYaKj4_+6e6Hg@mail.gmail.com/
> 
> Signed-off-by: Vlastimil Babka <vbabka@suse.cz>

Acked-by: Christian Borntraeger <borntraeger@de.ibm.com>

> ---
>  mm/slab_common.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/mm/slab_common.c b/mm/slab_common.c
> index 5282f881d2f5..ae9486160594 100644
> --- a/mm/slab_common.c
> +++ b/mm/slab_common.c
> @@ -1303,7 +1303,8 @@ void __init create_kmalloc_caches(slab_flags_t flags)
>  			kmalloc_caches[KMALLOC_DMA][i] = create_kmalloc_cache(
>  				kmalloc_info[i].name[KMALLOC_DMA],
>  				kmalloc_info[i].size,
> -				SLAB_CACHE_DMA | flags, 0, 0);
> +				SLAB_CACHE_DMA | flags, 0,
> +				kmalloc_info[i].size);
>  		}
>  	}
>  #endif
>