linux-kernel - Re: [PATCH v5 18/19] mm: Unpoison vms[area] addresses with a common tag

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: <2xfriqqibrl7pwvcn6f2zwfjromyuvlxas744vpqrn2jthbzu6@nrhlxafjpfnr>
Date: Mon, 8 Sep 2025 15:11:17 +0200
From: Maciej Wieczor-Retman <maciej.wieczor-retman@...el.com>
To: Andrey Konovalov <andreyknvl@...il.com>
CC: <sohil.mehta@...el.com>, <baohua@...nel.org>, <david@...hat.com>,
	<kbingham@...nel.org>, <weixugc@...gle.com>, <Liam.Howlett@...cle.com>,
	<alexandre.chartre@...cle.com>, <kas@...nel.org>, <mark.rutland@....com>,
	<trintaeoitogc@...il.com>, <axelrasmussen@...gle.com>, <yuanchu@...gle.com>,
	<joey.gouly@....com>, <samitolvanen@...gle.com>, <joel.granados@...nel.org>,
	<graf@...zon.com>, <vincenzo.frascino@....com>, <kees@...nel.org>,
	<ardb@...nel.org>, <thiago.bauermann@...aro.org>, <glider@...gle.com>,
	<thuth@...hat.com>, <kuan-ying.lee@...onical.com>,
	<pasha.tatashin@...een.com>, <nick.desaulniers+lkml@...il.com>,
	<vbabka@...e.cz>, <kaleshsingh@...gle.com>, <justinstitt@...gle.com>,
	<catalin.marinas@....com>, <alexander.shishkin@...ux.intel.com>,
	<samuel.holland@...ive.com>, <dave.hansen@...ux.intel.com>, <corbet@....net>,
	<xin@...or.com>, <dvyukov@...gle.com>, <tglx@...utronix.de>,
	<scott@...amperecomputing.com>, <jason.andryuk@....com>, <morbo@...gle.com>,
	<nathan@...nel.org>, <lorenzo.stoakes@...cle.com>, <mingo@...hat.com>,
	<brgerst@...il.com>, <kristina.martsenko@....com>, <bigeasy@...utronix.de>,
	<luto@...nel.org>, <jgross@...e.com>, <jpoimboe@...nel.org>,
	<urezki@...il.com>, <mhocko@...e.com>, <ada.coupriediaz@....com>,
	<hpa@...or.com>, <leitao@...ian.org>, <peterz@...radead.org>,
	<wangkefeng.wang@...wei.com>, <surenb@...gle.com>, <ziy@...dia.com>,
	<smostafa@...gle.com>, <ryabinin.a.a@...il.com>, <ubizjak@...il.com>,
	<jbohac@...e.cz>, <broonie@...nel.org>, <akpm@...ux-foundation.org>,
	<guoweikang.kernel@...il.com>, <rppt@...nel.org>, <pcc@...gle.com>,
	<jan.kiszka@...mens.com>, <nicolas.schier@...ux.dev>, <will@...nel.org>,
	<jhubbard@...dia.com>, <bp@...en8.de>, <x86@...nel.org>,
	<linux-doc@...r.kernel.org>, <linux-mm@...ck.org>, <llvm@...ts.linux.dev>,
	<linux-kbuild@...r.kernel.org>, <kasan-dev@...glegroups.com>,
	<linux-kernel@...r.kernel.org>, <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH v5 18/19] mm: Unpoison vms[area] addresses with a common
 tag

On 2025-09-06 at 19:19:11 +0200, Andrey Konovalov wrote:
>On Mon, Aug 25, 2025 at 10:31 PM Maciej Wieczor-Retman
><maciej.wieczor-retman@...el.com> wrote:
>>
>> The problem presented here is related to NUMA systems and tag-based
>> KASAN mode. It can be explained in the following points:
>>
>>         1. There can be more than one virtual memory chunk.
>>         2. Chunk's base address has a tag.
>>         3. The base address points at the first chunk and thus inherits
>>            the tag of the first chunk.
>>         4. The subsequent chunks will be accessed with the tag from the
>>            first chunk.
>>         5. Thus, the subsequent chunks need to have their tag set to
>>            match that of the first chunk.
>>
>> Unpoison all vms[]->addr memory and pointers with the same tag to
>> resolve the mismatch.
>>
>> Signed-off-by: Maciej Wieczor-Retman <maciej.wieczor-retman@...el.com>
>> ---
>> Changelog v4:
>> - Move tagging the vms[]->addr to this new patch and leave refactoring
>>   there.
>> - Comment the fix to provide some context.
>>
>>  mm/kasan/shadow.c | 10 +++++++++-
>>  1 file changed, 9 insertions(+), 1 deletion(-)
>>
>> diff --git a/mm/kasan/shadow.c b/mm/kasan/shadow.c
>> index b41f74d68916..ee2488371784 100644
>> --- a/mm/kasan/shadow.c
>> +++ b/mm/kasan/shadow.c
>> @@ -646,13 +646,21 @@ void __kasan_poison_vmalloc(const void *start, unsigned long size)
>>         kasan_poison(start, size, KASAN_VMALLOC_INVALID, false);
>>  }
>>
>> +/*
>> + * A tag mismatch happens when calculating per-cpu chunk addresses, because
>> + * they all inherit the tag from vms[0]->addr, even when nr_vms is bigger
>> + * than 1. This is a problem because all the vms[]->addr come from separate
>> + * allocations and have different tags so while the calculated address is
>> + * correct the tag isn't.
>> + */
>>  void __kasan_unpoison_vmap_areas(struct vm_struct **vms, int nr_vms)
>>  {
>>         int area;
>>
>>         for (area = 0 ; area < nr_vms ; area++) {
>>                 kasan_poison(vms[area]->addr, vms[area]->size,
>> -                            arch_kasan_get_tag(vms[area]->addr), false);
>> +                            arch_kasan_get_tag(vms[0]->addr), false);
>> +               arch_kasan_set_tag(vms[area]->addr, arch_kasan_get_tag(vms[0]->addr));
>>         }
>>  }
>>
>> --
>> 2.50.1
>>
>
>Do we need this fix for the HW_TAGS mode too?

Oh, I suppose it could also affect the hardware mode since this is related to
tagged pointers and NUMA nodes. I'll try to also make it work for HW_TAGS.

-- 
Kind regards
Maciej Wieczór-Retman