linux-kernel - Re: [PATCH] mm: move mask update out of the atomic context

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] [day] [month] [year] [list]

Message-ID: <4214d6d6-f8d5-43b3-a413-f576fdaf215d@redhat.com>
Date: Mon, 23 Jun 2025 21:45:34 +0200
From: David Hildenbrand <david@...hat.com>
To: Dev Jain <dev.jain@....com>, Alexander Gordeev <agordeev@...ux.ibm.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mm: move mask update out of the atomic context

On 23.06.25 12:09, Dev Jain wrote:
> 
> On 23/06/25 3:07 pm, Alexander Gordeev wrote:
>> On Mon, Jun 23, 2025 at 02:26:29PM +0530, Dev Jain wrote:
>>> On 23/06/25 1:34 pm, Alexander Gordeev wrote:
>>>> There is not need to modify page table synchronization mask
>>>> while apply_to_pte_range() holds user page tables spinlock.
>>> I don't get you, what is the problem with the current code?
>>> Are you just concerned about the duration of holding the
>>> lock?
>> Yes.
> 
> Doesn't really matter but still a correct change:

Let's ask the real questions: who checks PGTBL_PTE_MODIFIED?

I see

if (mask & ARCH_PAGE_TABLE_SYNC_MASK)
	arch_sync_kernel_mappings(start, start + size);

And then

arch/arm/include/asm/page.h:#define ARCH_PAGE_TABLE_SYNC_MASK   PGTBL_PMD_MODIFIED
arch/x86/include/asm/pgtable-2level_types.h:#define ARCH_PAGE_TABLE_SYNC_MASK   PGTBL_PMD_MODIFIED
arch/x86/include/asm/pgtable-3level_types.h:#define ARCH_PAGE_TABLE_SYNC_MASK   PGTBL_PMD_MODIFIED


Which makes me wonder why we need PGTBL_PTE_MODIFIED at all? Is there some other check I am missing?

(same question regarding everything excepy PGTBL_PMD_MODIFIED, because that actually seems to be used)

-- 
Cheers,

David / dhildenb