linux-kernel - Re: [PATCH 02/18] mm: make vm

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Message-ID: <20160311125533.GN27701@dhcp22.suse.cz>
Date:	Fri, 11 Mar 2016 13:55:33 +0100
From:	Michal Hocko <mhocko@...nel.org>
To:	Vlastimil Babka <vbabka@...e.cz>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
	Alex Deucher <alexander.deucher@....com>,
	Alex Thorlton <athorlton@....com>,
	Andrea Arcangeli <aarcange@...hat.com>,
	Andy Lutomirski <luto@...capital.net>,
	Benjamin LaHaise <bcrl@...ck.org>,
	Christian König <christian.koenig@....com>,
	Daniel Vetter <daniel.vetter@...el.com>,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	David Airlie <airlied@...ux.ie>,
	Davidlohr Bueso <dave@...olabs.net>,
	David Rientjes <rientjes@...gle.com>,
	"H . Peter Anvin" <hpa@...or.com>, Hugh Dickins <hughd@...gle.com>,
	Ingo Molnar <mingo@...nel.org>,
	Johannes Weiner <hannes@...xchg.org>,
	"Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>,
	Konstantin Khlebnikov <koct9i@...il.com>,
	linux-arch@...r.kernel.org, Mel Gorman <mgorman@...e.de>,
	Oleg Nesterov <oleg@...hat.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Petr Cermak <petrcermak@...omium.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Al Viro <viro@...iv.linux.org.uk>
Subject: Re: [PATCH 02/18] mm: make vm_mmap killable

On Fri 11-03-16 13:43:41, Vlastimil Babka wrote:
> On 03/11/2016 01:12 PM, Michal Hocko wrote:
> >On Fri 11-03-16 10:59:30, Vlastimil Babka wrote:
> >>On 02/29/2016 02:26 PM, Michal Hocko wrote:
> >>>From: Michal Hocko <mhocko@...e.com>
> >>>
> >>>All the callers of vm_mmap seem to check for the failure already
> >>>and bail out in one way or another on the error which means that
> >>
> >>Hmm I'm not that sure about this one:
> >>  17   1071  fs/binfmt_elf.c <<load_elf_binary>>
> >>
> >>Assigns result of vm_mmap() to "error" variable which is never checked.
> >
> >Yes it is not checked but not used either. If the current got killed
> >then it wouldn't return to the userspace so my understanding is that not
> >checking this value is not a problem. At least that is my understanding.
> 
> Hmm, that's true. So,

I have updated the changelog and added the following note:
"
Please note that load_elf_binary is ignoring vm_mmap error for 
current->personality & MMAP_PAGE_ZERO case but that shouldn't be a
problem because the address is not used anywhere and we never return to
the userspace if we got killed.
"
 
> Acked-by: Vlastimil Babka <vbabka@...e.cz>

Thanks!

-- 
Michal Hocko
SUSE Labs