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Message-ID: <20171207120735.GA24547@atrey.karlin.mff.cuni.cz> Date: Thu, 7 Dec 2017 13:07:35 +0100 From: Pavel Machek <pavel@....cz> To: Michal Hocko <mhocko@...nel.org> Cc: linux-api@...r.kernel.org, Khalid Aziz <khalid.aziz@...cle.com>, Michael Ellerman <mpe@...erman.id.au>, Andrew Morton <akpm@...ux-foundation.org>, Russell King - ARM Linux <linux@...linux.org.uk>, Andrea Arcangeli <aarcange@...hat.com>, linux-mm@...ck.org, LKML <linux-kernel@...r.kernel.org>, linux-arch@...r.kernel.org, Florian Weimer <fweimer@...hat.com>, John Hubbard <jhubbard@...dia.com>, Michal Hocko <mhocko@...e.com> Subject: Re: [PATCH 1/2] mm: introduce MAP_FIXED_SAFE Hi! > MAP_FIXED is used quite often to enforce mapping at the particular > range. The main problem of this flag is, however, that it is inherently > dangerous because it unmaps existing mappings covered by the requested > range. This can cause silent memory corruptions. Some of them even with > serious security implications. While the current semantic might be > really desiderable in many cases there are others which would want to > enforce the given range but rather see a failure than a silent memory > corruption on a clashing range. Please note that there is no guarantee > that a given range is obeyed by the mmap even when it is free - e.g. > arch specific code is allowed to apply an alignment. > > Introduce a new MAP_FIXED_SAFE flag for mmap to achieve this behavior. > It has the same semantic as MAP_FIXED wrt. the given address request Could we get some better name? Functionality seems reasonable, but _SAFE suffix does not really explain what is going on to the user. MAP_ADD_FIXED ? Pavel -- (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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