From mboxrd@z Thu Jan 1 00:00:00 1970 From: Mike Rapoport Subject: Re: [PATCH RFC] mm: add MAP_EXCLUSIVE to create exclusive user mappings Date: Mon, 28 Oct 2019 14:00:19 +0100 Message-ID: <20191028130018.GA7192@rapoport-lnx> References: <1572171452-7958-1-git-send-email-rppt@kernel.org> <1572171452-7958-2-git-send-email-rppt@kernel.org> <20191028123124.ogkk5ogjlamvwc2s@box> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <20191028123124.ogkk5ogjlamvwc2s@box> Sender: linux-kernel-owner@vger.kernel.org To: "Kirill A. Shutemov" Cc: linux-kernel@vger.kernel.org, Alexey Dobriyan , Andrew Morton , Andy Lutomirski , Arnd Bergmann , Borislav Petkov , Dave Hansen , James Bottomley , Peter Zijlstra , Steven Rostedt , Thomas Gleixner , Ingo Molnar , "H. Peter Anvin" , linux-api@vger.kernel.org, linux-mm@kvack.org, x86@kernel.org, Mike Rapoport List-Id: linux-api@vger.kernel.org On Mon, Oct 28, 2019 at 03:31:24PM +0300, Kirill A. Shutemov wrote: > On Sun, Oct 27, 2019 at 12:17:32PM +0200, Mike Rapoport wrote: > > From: Mike Rapoport > > > > The mappings created with MAP_EXCLUSIVE are visible only in the context of > > the owning process and can be used by applications to store secret > > information that will not be visible not only to other processes but to the > > kernel as well. > > > > The pages in these mappings are removed from the kernel direct map and > > marked with PG_user_exclusive flag. When the exclusive area is unmapped, > > the pages are mapped back into the direct map. > > I probably blind, but I don't see where you manipulate direct map... __get_user_pages() calls __set_page_user_exclusive() which in turn calls set_direct_map_invalid_noflush() that makes the page not present. > -- > Kirill A. Shutemov -- Sincerely yours, Mike.