From mboxrd@z Thu Jan 1 00:00:00 1970 From: luto@amacapital.net (Andy Lutomirski) Date: Tue, 3 Jan 2017 14:09:16 -0800 Subject: [RFC, PATCHv2 29/29] mm, x86: introduce RLIMIT_VADDR In-Reply-To: <21511994.eBlbEPoKOz@wuerfel> References: <20161227015413.187403-1-kirill.shutemov@linux.intel.com> <3492795.xaneWtGxgW@wuerfel> <21511994.eBlbEPoKOz@wuerfel> Message-ID: To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On Tue, Jan 3, 2017 at 2:07 PM, Arnd Bergmann wrote: > On Tuesday, January 3, 2017 10:29:33 AM CET Andy Lutomirski wrote: >> >> Hmm. What if we approached this a bit differently? We could add a >> single new personality bit ADDR_LIMIT_EXPLICIT. Setting this bit >> cause PER_LINUX32_3GB etc to be automatically cleared. > > Both the ADDR_LIMIT_32BIT and ADDR_LIMIT_3GB flags I guess? Yes. > >> When >> ADDR_LIMIT_EXPLICIT is in effect, prctl can set a 64-bit numeric >> limit. If ADDR_LIMIT_EXPLICIT is cleared, the prctl value stops being >> settable and reading it via prctl returns whatever is implied by the >> other personality bits. > > I don't see anything wrong with it, but I'm a bit confused now > what this would be good for, compared to using just prctl. > > Is this about setuid clearing the personality but not the prctl, > or something else? It's to avid ambiguity as to what happens if you set ADDR_LIMIT_32BIT and use the prctl. ISTM it would be nice for the semantics to be fully defined in all cases. --Andy