From mboxrd@z Thu Jan 1 00:00:00 1970 From: leif.lindholm@linaro.org (Leif Lindholm) Date: Fri, 20 Jan 2017 14:42:45 +0000 Subject: [PATCH] arm64: defconfig: disable CONFIG_DEVMEM In-Reply-To: <20170119094917.GA11954@arm.com> References: <20170113113734.16524-1-leif.lindholm@linaro.org> <20170113114801.GD3253@arm.com> <20170115124254.GF25883@bivouac.eciton.net> <20170119094917.GA11954@arm.com> Message-ID: <20170120144245.GG25883@bivouac.eciton.net> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On Thu, Jan 19, 2017 at 09:49:17AM +0000, Will Deacon wrote: > On Wed, Jan 18, 2017 at 05:58:05PM +0000, Leif Lindholm wrote: > > On 15 January 2017 at 12:42, Leif Lindholm wrote: > > > On Fri, Jan 13, 2017 at 11:48:01AM +0000, Will Deacon wrote: > > >> On Fri, Jan 13, 2017 at 11:37:34AM +0000, Leif Lindholm wrote: > > >> > /dev/mem is the opposite of what an operating system is for. > > >> > Additionally, on arm* it opens up for denial-of-service attacks from > > >> > userspace. So leave it disabled by default, requiring people who need > > >> > it to enable it explicitly. > > >> > > >> I really like the idea, but are we sure that nothing common breaks without > > >> this? For example, does Debian still boot nicely with this patch applied? > > > > > > Getting distros to not have to shop around for config fragments in > > > order to be able to a stable system is one of my main purposes of this > > > patch. > > > > > > Since Debian just published a 4.9 kernel, I gave that a spin (both DT > > > and ACPI). No issues. > > > > Will, any comments? > > Nope; fine by me. arm-soc usually pick these up. Arnd, Olof? > FWIW, I did do a Debian CodeSearch for /dev/mem and there were more hits > than I was hoping for. However, much of the code looked either: > > (a) Broken anyway > (b) Not relevant to arm64 > (c) /dev/mem was just a string in a comment or something > > There are a couple of crazy projects that appear to use /dev/mem to > implement a heap, but I really couldn't figure out how that worked. Yeah, I noticed those too. I don't think they do. / Leif