From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S965419Ab2CBO0j (ORCPT ); Fri, 2 Mar 2012 09:26:39 -0500 Received: from mail-bk0-f46.google.com ([209.85.214.46]:42323 "EHLO mail-bk0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757915Ab2CBO0f (ORCPT ); Fri, 2 Mar 2012 09:26:35 -0500 Authentication-Results: mr.google.com; spf=pass (google.com: domain of gorcunov@gmail.com designates 10.204.148.89 as permitted sender) smtp.mail=gorcunov@gmail.com; dkim=pass header.i=gorcunov@gmail.com Date: Fri, 2 Mar 2012 18:26:30 +0400 From: Cyrill Gorcunov To: Oleg Nesterov Cc: LKML , Andrew Morton , KOSAKI Motohiro , Pavel Emelyanov , Kees Cook , Tejun Heo Subject: Re: [RFC] c/r: prctl: Add ability to set new mm_struct::exe_file Message-ID: <20120302142630.GK8681@moon> References: <20120229151634.GE4796@moon> <20120229192400.GA13194@redhat.com> <20120229200103.GJ11326@moon> <20120301180616.GA7652@redhat.com> <20120301191714.GF9930@moon> <20120301194120.GA11400@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20120301194120.GA11400@redhat.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Mar 01, 2012 at 08:41:20PM +0100, Oleg Nesterov wrote: ... > Still can't understand. I think you need: > > file = fget(fd); > if (!file) > return -EBADF; > > down_write(&mm->mmap_sem); > if (mm->num_exe_file_vmas) { > fput(mm->exe_file); > mm->exe_file = file; > file = NULL; > } > up_write(&mm->mmap_sem); > > if (!file) > return 0; > > fput(file); > return -ESOMETHING; > > and that is all. Hi Oleg, sure you were right. I even think testing for num_exe_file_vmas is not needed, since until real executable VMA is read and mapped it might remain zero. So I guess something like below should work. Cyrill --- From: Cyrill Gorcunov Subject: c/r: prctl: Add ability to set new mm_struct::exe_file v2 When we do restore we would like to have a way to setup a former mm_struct::exe_file so that /proc/pid/exe would point to the original executable file a process had at checkpoint time. For this sake PR_SET_MM_EXE_FILE code is introduced. This feature is available iif CONFIG_CHECKPOINT_RESTORE is set. Signed-off-by: Cyrill Gorcunov CC: Oleg Nesterov CC: KOSAKI Motohiro CC: Pavel Emelyanov CC: Kees Cook CC: Tejun Heo --- include/linux/prctl.h | 1 + kernel/sys.c | 24 ++++++++++++++++++++++++ 2 files changed, 25 insertions(+) Index: linux-2.6.git/include/linux/prctl.h =================================================================== --- linux-2.6.git.orig/include/linux/prctl.h +++ linux-2.6.git/include/linux/prctl.h @@ -118,5 +118,6 @@ # define PR_SET_MM_ENV_START 10 # define PR_SET_MM_ENV_END 11 # define PR_SET_MM_AUXV 12 +# define PR_SET_MM_EXE_FILE 13 #endif /* _LINUX_PRCTL_H */ Index: linux-2.6.git/kernel/sys.c =================================================================== --- linux-2.6.git.orig/kernel/sys.c +++ linux-2.6.git/kernel/sys.c @@ -36,6 +36,7 @@ #include #include #include +#include #include #include #include @@ -1701,6 +1702,25 @@ static bool vma_flags_mismatch(struct vm (vma->vm_flags & banned); } +static int prctl_set_mm_exe_file(struct mm_struct *mm, unsigned int fd) +{ + struct file *new_exe_file, *old_exe_file; + + new_exe_file = fget(fd); + if (!new_exe_file) + return -EBADF; + + down_write(&mm->mmap_sem); + old_exe_file = mm->exe_file; + mm->exe_file = new_exe_file; + up_write(&mm->mmap_sem); + + if (old_exe_file) + fput(old_exe_file); + + return 0; +} + static int prctl_set_mm(int opt, unsigned long addr, unsigned long arg4, unsigned long arg5) { @@ -1715,6 +1735,9 @@ static int prctl_set_mm(int opt, unsigne if (!capable(CAP_SYS_ADMIN)) return -EPERM; + if (opt == PR_SET_MM_EXE_FILE) + return prctl_set_mm_exe_file(mm, (unsigned int)addr); + if (addr >= TASK_SIZE) return -EINVAL; @@ -1837,6 +1860,7 @@ static int prctl_set_mm(int opt, unsigne return 0; } + default: error = -EINVAL; goto out;