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;
Received-SPF: None (esa4.hc3370-68.iphmx.com: no sender
  authenticity information available from domain of
  sergey.dyasli@citrix.com) identity=pra;
  client-ip=162.221.158.21; receiver=esa4.hc3370-68.iphmx.com;
  envelope-from="sergey.dyasli@citrix.com";
  x-sender="sergey.dyasli@citrix.com";
  x-conformance=sidf_compatible
Received-SPF: Pass (esa4.hc3370-68.iphmx.com: domain of
  sergey.dyasli@citrix.com designates 162.221.158.21 as
  permitted sender) identity=mailfrom;
  client-ip=162.221.158.21; receiver=esa4.hc3370-68.iphmx.com;
  envelope-from="sergey.dyasli@citrix.com";
  x-sender="sergey.dyasli@citrix.com";
  x-conformance=sidf_compatible; x-record-type="v=spf1";
  x-record-text="v=spf1 ip4:209.167.231.154 ip4:178.63.86.133
  ip4:195.66.111.40/30 ip4:85.115.9.32/28 ip4:199.102.83.4
  ip4:192.28.146.160 ip4:192.28.146.107 ip4:216.52.6.88
  ip4:216.52.6.188 ip4:162.221.158.21 ip4:162.221.156.83
  ip4:168.245.78.127 ~all"
Received-SPF: None (esa4.hc3370-68.iphmx.com: no sender
  authenticity information available from domain of
  postmaster@mail.citrix.com) identity=helo;
  client-ip=162.221.158.21; receiver=esa4.hc3370-68.iphmx.com;
  envelope-from="sergey.dyasli@citrix.com";
  x-sender="postmaster@mail.citrix.com";
  x-conformance=sidf_compatible
IronPort-SDR: +bTwz3rb6Pt3yrpWyywqXjEWMAEX4c/82keB2YSJFPUWl/kcbbp2jzBF6YJLhblAe5aQQSPmR7
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 J10=
Subject: Re: [PATCH v1 4/4] xen/netback: Fix grant copy across page boundary
 with KASAN
To:     Vlastimil Babka <vbabka@suse.cz>, <xen-devel@lists.xen.org>,
        <kasan-dev@googlegroups.com>, <linux-mm@kvack.org>,
        <linux-kernel@vger.kernel.org>
CC:     Andrey Ryabinin <aryabinin@virtuozzo.com>,
        Alexander Potapenko <glider@google.com>,
        Dmitry Vyukov <dvyukov@google.com>,
        Boris Ostrovsky <boris.ostrovsky@oracle.com>,
        Juergen Gross <jgross@suse.com>,
        "Stefano Stabellini" <sstabellini@kernel.org>,
        George Dunlap <george.dunlap@citrix.com>,
        Ross Lagerwall <ross.lagerwall@citrix.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Wei Liu <wei.liu@kernel.org>, "Paul Durrant" <paul@xen.org>,
        "sergey.dyasli@citrix.com >> Sergey Dyasli" 
        <sergey.dyasli@citrix.com>
References: <20200108152100.7630-1-sergey.dyasli@citrix.com>
 <20200108152100.7630-5-sergey.dyasli@citrix.com>
 <26c43c43-b303-938c-2f26-8e0144159e29@suse.cz>
From:   Sergey Dyasli <sergey.dyasli@citrix.com>
Autocrypt: addr=sergey.dyasli@citrix.com; keydata=
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Message-ID: <e0663153-35e0-32ef-87a5-39189c440a3d@citrix.com>
Date:   Wed, 15 Jan 2020 11:02:59 +0000
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Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

On 09/01/2020 10:33, Vlastimil Babka wrote:
> On 1/8/20 4:21 PM, Sergey Dyasli wrote:
>> From: Ross Lagerwall <ross.lagerwall@citrix.com>
>>
>> When KASAN (or SLUB_DEBUG) is turned on, the normal expectation that
>> allocations are aligned to the next power of 2 of the size does not
>> hold.
>
> Hmm, really? They should after 59bb47985c1d ("mm, sl[aou]b: guarantee
> natural alignment for kmalloc(power-of-two)"), i.e. since 5.4.
>
> But actually the guarantee is only for precise power of two sizes given
> to kmalloc(). Allocations of sizes that end up using the 96 or 192 bytes
> kmalloc cache have no such guarantee. But those might then cross page
> boundary also without SLUB_DEBUG.

That's interesting to know. It's certainly not the case for 4.19 kernel
for which PV KASAN was initially developed. But I guess this means that
only patch description needs updating.

>
>> Therefore, handle grant copies that cross page boundaries.
>>
>> Signed-off-by: Ross Lagerwall <ross.lagerwall@citrix.com>
>> Signed-off-by: Sergey Dyasli <sergey.dyasli@citrix.com>

--
Thanks,
Sergey