linux-kernel - Re: [PATCH v11 3/8] highmem: introduce clear_user

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: <87pl7kr5x1.fsf@oracle.com>
Date: Wed, 07 Jan 2026 22:10:18 -0800
From: Ankur Arora <ankur.a.arora@...cle.com>
To: "David Hildenbrand (Red Hat)" <david@...nel.org>
Cc: Ankur Arora <ankur.a.arora@...cle.com>, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org, x86@...nel.org, akpm@...ux-foundation.org,
        bp@...en8.de, dave.hansen@...ux.intel.com, hpa@...or.com,
        mingo@...hat.com, mjguzik@...il.com, luto@...nel.org,
        peterz@...radead.org, tglx@...utronix.de, willy@...radead.org,
        raghavendra.kt@....com, chleroy@...nel.org, ioworker0@...il.com,
        lizhe.67@...edance.com, boris.ostrovsky@...cle.com,
        konrad.wilk@...cle.com
Subject: Re: [PATCH v11 3/8] highmem: introduce clear_user_highpages()


David Hildenbrand (Red Hat) <david@...nel.org> writes:

> On 1/7/26 08:20, Ankur Arora wrote:
>> Define clear_user_highpages() which uses the range clearing primitive,
>> clear_user_pages(). We can safely use this when CONFIG_HIGHMEM is
>> disabled and if the architecture does not have clear_user_highpage.
>> The first is needed to ensure that contiguous page ranges stay
>> contiguous which precludes intermediate maps via HIGMEM.
>> The second, because if the architecture has clear_user_highpage(),
>> it likely needs flushing magic when clearing the page, magic that
>> we aren't privy to.
>> For both of those cases, just fallback to a loop around
>> clear_user_highpage().
>> Signed-off-by: Ankur Arora <ankur.a.arora@...cle.com>
>> ---
>>   include/linux/highmem.h | 45 ++++++++++++++++++++++++++++++++++++++++-
>>   1 file changed, 44 insertions(+), 1 deletion(-)
>> diff --git a/include/linux/highmem.h b/include/linux/highmem.h
>> index 019ab7d8c841..af03db851a1d 100644
>> --- a/include/linux/highmem.h
>> +++ b/include/linux/highmem.h
>> @@ -251,7 +251,14 @@ static inline void clear_user_pages(void *addr, unsigned long vaddr,
>>   #endif
>>   }
>>   -/* when CONFIG_HIGHMEM is not set these will be plain clear/copy_page */
>> +/**
>> + * clear_user_highpage() - clear a page to be mapped to user space
>
> Just a minor comment as I am skimming the patches: I recall kerneldoc does not
> require the "()" here. But I also recall that it doesn't hurt :)

Thanks. I had assumed that the "()" was required. Just now grepped to see
which style is more common and found that I had used both of them in just
this series :).

> Acked-by: David Hildenbrand (Red Hat) <david@...nel.org>

Thanks for all the acks!

--
ankur