linux-kernel - Re: [PATCH] mm/gup: stop leaking pinned pages in low memory conditions

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Message-Id: <20241016154127.3e369be7398bd0c3db27e8e3@linux-foundation.org>
Date: Wed, 16 Oct 2024 15:41:27 -0700
From: Andrew Morton <akpm@...ux-foundation.org>
To: John Hubbard <jhubbard@...dia.com>
Cc: LKML <linux-kernel@...r.kernel.org>, linux-mm@...ck.org, Alistair Popple
 <apopple@...dia.com>, Shigeru Yoshida <syoshida@...hat.com>, David
 Hildenbrand <david@...hat.com>, Jason Gunthorpe <jgg@...dia.com>, Minchan
 Kim <minchan@...nel.org>, Pasha Tatashin <pasha.tatashin@...een.com>
Subject: Re: [PATCH] mm/gup: stop leaking pinned pages in low memory
 conditions

On Wed, 16 Oct 2024 15:05:28 -0700 John Hubbard <jhubbard@...dia.com> wrote:

> On 10/16/24 2:57 PM, Andrew Morton wrote:
> > On Wed, 16 Oct 2024 13:22:42 -0700 John Hubbard <jhubbard@...dia.com> wrote:
> ...
> >> Fix this by unpinning the pages that __get_user_pages_locked() has
> >> pinned, in such error cases.
> > 
> > Thanks.
> > 
> >> Fixes: 24a95998e9ba ("mm/gup.c: simplify and fix check_and_migrate_movable_pages() return codes")
> > 
> > I'll add this to the -stable backport pile, although this seems a bit
> > marginal?
> 
> I'm on the fence about that. It is marginal: you have to
> exhaust memory. On the other hand, a real user reported
> this bug to us.
> 
> I guess I'd lean toward "correctness in -stable", and
> add it to the pile, in the end.

Thanks.  It's a super-simple patch, which helps the decision.