Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933633Ab2BBX1L (ORCPT ); Thu, 2 Feb 2012 18:27:11 -0500 Received: from mail.linuxfoundation.org ([140.211.169.12]:38392 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932145Ab2BBX1H (ORCPT ); Thu, 2 Feb 2012 18:27:07 -0500 Date: Thu, 2 Feb 2012 15:27:05 -0800 From: Andrew Morton To: Cyrill Gorcunov Cc: linux-kernel@vger.kernel.org, Pavel Emelyanov , Serge Hallyn , KAMEZAWA Hiroyuki , Kees Cook , Tejun Heo , Andrew Vagin , "Eric W. Biederman" , Alexey Dobriyan , Andi Kleen , Michael Kerrisk , Vasiliy Kulikov Subject: Re: [patch cr 4/4] c/r: prctl: Extend PR_SET_MM to set up more mm_struct entries Message-Id: <20120202152705.831b00c7.akpm@linux-foundation.org> In-Reply-To: <20120130141852.466613862@openvz.org> References: <20120130140905.441199885@openvz.org> <20120130141852.466613862@openvz.org> X-Mailer: Sylpheed 3.0.2 (GTK+ 2.20.1; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2832 Lines: 95 On Mon, 30 Jan 2012 18:09:09 +0400 Cyrill Gorcunov wrote: > After restore we would like the 'ps' command show the command > line and evironment exactly the same it was at checkpoint time. > > So this additional PR_SET_MM_ allow us to do so. Note that > these members of mm_struct is rather used for output in > procfs, except auxv vector which is used by ld.so mostly. This changelog is pretty darned hard to understand. Can we have a version 2 please? > > ... > > @@ -1753,19 +1755,6 @@ static int prctl_set_mm(int opt, unsigne > mm->end_data = addr; > break; > > - case PR_SET_MM_START_STACK: > - > -#ifdef CONFIG_STACK_GROWSUP > - vm_req_flags = VM_READ | VM_WRITE | VM_GROWSUP; > -#else > - vm_req_flags = VM_READ | VM_WRITE | VM_GROWSDOWN; > -#endif > - if ((vma->vm_flags & vm_req_flags) != vm_req_flags) > - goto out; > - > - mm->start_stack = addr; > - break; > - > case PR_SET_MM_START_BRK: > if (addr <= mm->end_data) > goto out; > @@ -1790,16 +1779,53 @@ static int prctl_set_mm(int opt, unsigne > mm->brk = addr; > break; Here would be a good place to add some nice comments explaining what these do. Although I guess that isn't needed if one can get that info by typing "man prctl". > + case PR_SET_MM_START_STACK: > + case PR_SET_MM_ARG_START: > + case PR_SET_MM_ARG_END: > + case PR_SET_MM_ENV_START: > + case PR_SET_MM_ENV_END: > +#ifdef CONFIG_STACK_GROWSUP > + if (vma_flags_mismatch(vma, VM_READ | VM_WRITE | VM_GROWSUP, 0)) > +#else > + if (vma_flags_mismatch(vma, VM_READ | VM_WRITE | VM_GROWSDOWN, 0)) > +#endif > + goto out; > + if (opt == PR_SET_MM_START_STACK) > + mm->start_stack = addr; > + else if (opt == PR_SET_MM_ARG_START) > + mm->arg_start = addr; > + else if (opt == PR_SET_MM_ARG_END) > + mm->arg_end = addr; > + else if (opt == PR_SET_MM_ENV_START) > + mm->env_start = addr; > + else if (opt == PR_SET_MM_ENV_END) > + mm->env_end = addr; > + break; > + > + case PR_SET_MM_AUXV: { > + unsigned long user_auxv[AT_VECTOR_SIZE]; > + > + if (arg4 > sizeof(mm->saved_auxv)) > + goto out; > + up_read(&mm->mmap_sem); > + > + if (copy_from_user(user_auxv, (const void __user *)addr, arg4)) > + return EFAULT; > + > + task_lock(current); > + memcpy(mm->saved_auxv, user_auxv, arg4); > + task_unlock(current); > + > + return 0; > + } I worry a bit about this. We're giving userspace the ability to modify various mm_struct fields. Userspace can already do this via exec(elf-file), but perhaps this opens up a way in which userspace can newly trigger kernel bugs. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/