linux-kernel - Re: [PATCH] mm: Respect FOLL_FORCE/FOLL

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]

Date:   Thu, 5 Jan 2017 16:06:06 -0500
From:   Keno Fischer <keno@...iacomputing.com>
To:     "Kirill A. Shutemov" <kirill@...temov.name>
Cc:     linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        torvalds@...ux-foundation.org, Greg Thelen <gthelen@...gle.com>,
        npiggin@...il.com, Willy Tarreau <w@....eu>,
        Oleg Nesterov <oleg@...hat.com>,
        Kees Cook <keescook@...omium.org>, luto@...nel.org,
        mhocko@...e.com, Hugh Dickins <hughd@...gle.com>
Subject: Re: [PATCH] mm: Respect FOLL_FORCE/FOLL_COW for thp

>> @@ -783,7 +793,7 @@ struct page *follow_devmap_pmd(struct vm_area_struct *vma, unsigned long addr,
>>
>>       assert_spin_locked(pmd_lockptr(mm, pmd));
>>
>> -     if (flags & FOLL_WRITE && !pmd_write(*pmd))
>> +     if (flags & FOLL_WRITE && !can_follow_write_pmd(*pmd, flags))
>>               return NULL;
>
> I don't think this part is needed: once we COW devmap PMD entry, we split
> it into PTE table, so IIUC we never get here with PMD.
>
> Maybe we should WARN_ONCE() if have FOLL_COW here.

Sounds good to me. As I said, I don't have a testcase for this code
path, I just noticed the same pattern.
Will send an updated patch with the WARN_ONCE there.