linux-kernel - Re: [PATCH] vmap(): don't allow invalid pages

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: <5b62ed03-8da8-a94d-cc48-a8cac1eae1c9@arm.com>
Date:   Thu, 20 Jan 2022 09:07:11 +0530
From:   Anshuman Khandual <anshuman.khandual@....com>
To:     Yury Norov <yury.norov@...il.com>
Cc:     Matthew Wilcox <willy@...radead.org>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Nicholas Piggin <npiggin@...il.com>,
        Ding Tianhong <dingtianhong@...wei.com>,
        Alexey Klimov <aklimov@...hat.com>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org, Uladzislau Rezki <urezki@...il.com>
Subject: Re: [PATCH] vmap(): don't allow invalid pages



On 1/19/22 10:52 PM, Yury Norov wrote:
>> Why should not this just scan over the entire user provided struct page
>> array and make sure that all pages there in are valid via above method,
>> but in vmap() itself before calling vmap_pages_range(). Because seems
>> like a single invalid page detected in vmap_pages_pte_range() will
>> anyways abort the entire vmap(). This will also enable us to drop the
>> existing NULL check above.
>
> I can do this, but why is it any better than the current approach?

Because it will just return on the first instance where the valid page
check fails, saving us some CPU cycles and an incomplete mapping ?