From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758420AbdJQM4J (ORCPT ); Tue, 17 Oct 2017 08:56:09 -0400 Received: from mx2.suse.de ([195.135.220.15]:34953 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754092AbdJQM4I (ORCPT ); Tue, 17 Oct 2017 08:56:08 -0400 Date: Tue, 17 Oct 2017 14:56:05 +0200 From: Michal Hocko To: Baoquan He Cc: LKML , Linus Torvalds , Kees Cook , Jiri Kosina , Al Viro , Oleg Nesterov , Ingo Molnar Subject: Re: [PATCH 1/2] fs, elf: drop MAP_FIXED usage from elf_map Message-ID: <20171017125605.7quzqa3swvagyeiq@dhcp22.suse.cz> References: <20171004075059.bbx7madwgwflb7ky@dhcp22.suse.cz> <20171016134446.19910-1-mhocko@kernel.org> <20171016134446.19910-2-mhocko@kernel.org> <20171017122614.GJ11198@x1> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20171017122614.GJ11198@x1> User-Agent: NeoMutt/20170609 (1.8.3) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue 17-10-17 20:26:14, Baoquan He wrote: > Hi Michal, > > Earlier I posted a patchset to clean up these in a different way, but > patches sent to your below mail address are all rejected. > > : host mail.kerne.org[104.131.33.237] said: 454 4.1.1 > : Recipient address rejected: User unknown in virtual > mailbox table (in reply to RCPT TO command) yes, there was a typo in the email address which I've fixed up in the reply... Your cleanup was mostly about replacing vm_mmap by get_unmaped_area which is an independent issue to what I am trying to achieve here. > On 10/16/17 at 03:44pm, Michal Hocko wrote: > > From: Michal Hocko > > diff --git a/fs/binfmt_elf.c b/fs/binfmt_elf.c > > index 6466153f2bf0..09456e2add18 100644 > > --- a/fs/binfmt_elf.c > > +++ b/fs/binfmt_elf.c > > @@ -341,6 +341,29 @@ create_elf_tables(struct linux_binprm *bprm, struct elfhdr *exec, > > > > #ifndef elf_map > > > > +static unsigned long elf_vm_mmap(struct file *filep, unsigned long addr, > > + unsigned long size, int prot, int type, unsigned long off) > > +{ > > + unsigned long map_addr; > > + > > + /* > > + * If caller requests the mapping at a specific place, make sure we fail > > + * rather than potentially clobber an existing mapping which can have > > + * security consequences (e.g. smash over the stack area). > > + */ > > + map_addr = vm_mmap(filep, addr, size, prot, type & ~MAP_FIXED, off); > > + if (BAD_ADDR(map_addr)) > > + return map_addr; > > + > > + if ((type & MAP_FIXED) && map_addr != addr) { > > + pr_info("Uhuuh, elf segement at %p requested but the memory is mapped already\n", > > + (void*)addr); > > + return -EAGAIN; > > + } > > + > > + return map_addr; > > +} > > + > > static unsigned long elf_map(struct file *filep, unsigned long addr, > > struct elf_phdr *eppnt, int prot, int type, > > unsigned long total_size) > > @@ -366,11 +389,11 @@ static unsigned long elf_map(struct file *filep, unsigned long addr, > > */ > > if (total_size) { > > total_size = ELF_PAGEALIGN(total_size); > > - map_addr = vm_mmap(filep, addr, total_size, prot, type, off); > > + map_addr = elf_vm_mmap(filep, addr, total_size, prot, type, off); > > if (!BAD_ADDR(map_addr)) > > vm_munmap(map_addr+size, total_size-size); > > Here we will still take the map total, then unmap the rest way. > > I am wondering why we don't fix those issues we figured out, but add > another level of wrapper elf_vm_mmap() to hack it. Could you be more specific please? > So we will have > elf_map() -> elf_vm_mmap() -> vm_mmap(), not even counting > vm_mmap_pgoff(), then finally enter into do_mmap_pgoff(), to do the > maping for elf program. I've added another level of helper to keep the code in elf_map saner. It is quite complex already. -- Michal Hocko SUSE Labs