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From: Roman Gushchin <guro@fb.com>
To: Greg KH <gregkh@linuxfoundation.org>
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Subject: Re: FAILED: patch "[PATCH] mm: treat indirectly reclaimable memory as
 free in overcommit" failed to apply to 4.16-stable tree
Date: Thu, 11 Oct 2018 21:04:17 +0000
Message-ID: <20181011210409.GA4320@tower.DHCP.thefacebook.com>
References: <1526132159220203@kroah.com> <20180514104553.GA28956@castle>
 <20181011142746.GE9507@kroah.com>
In-Reply-To: <20181011142746.GE9507@kroah.com>
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On Thu, Oct 11, 2018 at 04:27:46PM +0200, Greg KH wrote:
> On Mon, May 14, 2018 at 11:46:00AM +0100, Roman Gushchin wrote:
> > On Sat, May 12, 2018 at 03:35:59PM +0200, gregkh@linuxfoundation.org wr=
ote:
> > >=20
> > > The patch below does not apply to the 4.16-stable tree.
> > > If someone wants it applied there, or to any other stable or longterm
> > > tree, then please email the backport, including the original git comm=
it
> > > id to <stable@vger.kernel.org>.
> > >=20
> > > thanks,
> > >=20
> > > greg k-h
> >=20
> > Hi, Greg!
> >=20
> > This patch is a part of the following patchset:
> > 7aaf77272358 mm: don't show nr_indirectly_reclaimable in /proc/vmstat
> > d79f7aa496fc mm: treat indirectly reclaimable memory as free in overcom=
mit logic
> > f1782c9bc547 dcache: account external names as indirectly reclaimable m=
emory
> > 034ebf65c3c2 mm: treat indirectly reclaimable memory as available in Me=
mAvailable
> > eb59254608bc mm: introduce NR_INDIRECTLY_RECLAIMABLE_BYTES
> >=20
> > It should be backported as a whole. It applies cleanly on 4.16-stable,
> > and with a minor trivial adjustment to 4.14-stable.
>=20
> Sorry for the long delay, digging out of my stable backlog...
>=20
> Anyway, is this still needed for 4.14-stable?

There is a security issue, which these patches are closing. It allows to ca=
use
a system-wide memory allocation failure, if overcommit logic is enabled and
it's possible to create negative dentries (e.g. asking httpd for non-existi=
ng
files). The issue is very old and exists in most stable branches, so Idk ho=
w
bad is to leave it open in 4.14.
Anyway, please, let me know if I can help somehow.

Thanks!