linux-kernel - Re: [PATCH V5 0/7] Allow user to request memory to be locked on page fault

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 for Android: free password hash cracker in your pocket

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Tue, 28 Jul 2015 13:17:25 +0200
From:	Michal Hocko <mhocko@...nel.org>
To:	Eric B Munson <emunson@...mai.com>
Cc:	Vlastimil Babka <vbabka@...e.cz>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Shuah Khan <shuahkh@....samsung.com>,
	Michael Kerrisk <mtk.manpages@...il.com>,
	Jonathan Corbet <corbet@....net>,
	Ralf Baechle <ralf@...ux-mips.org>,
	linux-alpha@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-mips@...ux-mips.org, linux-parisc@...r.kernel.org,
	linuxppc-dev@...ts.ozlabs.org, sparclinux@...r.kernel.org,
	linux-xtensa@...ux-xtensa.org, linux-mm@...ck.org,
	linux-arch@...r.kernel.org, linux-api@...r.kernel.org
Subject: Re: [PATCH V5 0/7] Allow user to request memory to be locked on page
 fault

[I am sorry but I didn't get to this sooner.]

On Mon 27-07-15 10:54:09, Eric B Munson wrote:
> Now that VM_LOCKONFAULT is a modifier to VM_LOCKED and
> cannot be specified independentally, it might make more sense to mirror
> that relationship to userspace.  Which would lead to soemthing like the
> following:

A modifier makes more sense.
 
> To lock and populate a region:
> mlock2(start, len, 0);
> 
> To lock on fault a region:
> mlock2(start, len, MLOCK_ONFAULT);
> 
> If LOCKONFAULT is seen as a modifier to mlock, then having the flags
> argument as 0 mean do mlock classic makes more sense to me.
> 
> To mlock current on fault only:
> mlockall(MCL_CURRENT | MCL_ONFAULT);
> 
> To mlock future on fault only:
> mlockall(MCL_FUTURE | MCL_ONFAULT);
> 
> To lock everything on fault:
> mlockall(MCL_CURRENT | MCL_FUTURE | MCL_ONFAULT);

Makes sense to me. The only remaining and still tricky part would be
the munlock{all}(flags) behavior. What should munlock(MLOCK_ONFAULT)
do? Keep locked and poppulate the range or simply ignore the flag an
just unlock?

I can see some sense to allow munlockall(MCL_FUTURE[|MLOCK_ONFAULT]),
munlockall(MCL_CURRENT) resp. munlockall(MCL_CURRENT|MCL_FUTURE) but
other combinations sound weird to me.

Anyway munlock with flags opens new doors of trickiness.
-- 
Michal Hocko
SUSE Labs
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/