From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754011Ab2CCWdj (ORCPT ); Sat, 3 Mar 2012 17:33:39 -0500 Received: from mail-bk0-f46.google.com ([209.85.214.46]:54253 "EHLO mail-bk0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752380Ab2CCWdi (ORCPT ); Sat, 3 Mar 2012 17:33:38 -0500 Authentication-Results: mr.google.com; spf=pass (google.com: domain of gorcunov@gmail.com designates 10.204.133.196 as permitted sender) smtp.mail=gorcunov@gmail.com; dkim=pass header.i=gorcunov@gmail.com Date: Sun, 4 Mar 2012 02:33:33 +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: <20120303223333.GB26846@moon> References: <20120229151634.GE4796@moon> <20120229192400.GA13194@redhat.com> <20120229200103.GJ11326@moon> <20120301180616.GA7652@redhat.com> <20120301191714.GF9930@moon> <20120301194120.GA11400@redhat.com> <20120302142630.GK8681@moon> <20120302152621.GA29744@redhat.com> <20120302161247.GO8681@moon> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20120302161247.GO8681@moon> 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 Fri, Mar 02, 2012 at 08:12:47PM +0400, Cyrill Gorcunov wrote: ... > > Yes, Oleg, you're right of course! The set_mm_exe_file confused > me a bit (I didn't reply to your previous emails simply because > you were asking me to prove what exactly is broken when num_exe_file_vmas > greater 2 and we reassign new exe_file, and I didn't know what to reply > since I knew I was wrong in first assumption). > > As a conclusion -- sure I need to check for num_exe_file_vmas to > not break current logic, thanks! > Hi Oleg, i suppose the below one should do the trick. I mostly concerned at moment if I added all permission tests needed. Cyrill --- c/r: prctl: Add ability to set new mm_struct::exe_file v2 From: Cyrill Gorcunov 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 the 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 | 56 ++++++++++++++++++++++++++++++++++++++++++++++++++ 2 files changed, 57 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 +36,8 @@ #include #include #include +#include +#include #include #include #include @@ -1701,6 +1703,56 @@ 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 *exe_file; + struct dentry *dentry; + int err; + + exe_file = fget(fd); + if (!exe_file) + return -EBADF; + + dentry = exe_file->f_path.dentry; + + /* + * Permissions should be the same as if the + * file has being opened by the kernel for + * execution. + */ + err = -EACCES; + if (!S_ISREG(dentry->d_inode->i_mode) || + exe_file->f_path.mnt->mnt_flags & MNT_NOEXEC) + goto exit; + + if ((exe_file->f_flags & O_ACCMODE) != O_RDONLY) + goto exit; + + err = inode_permission(dentry->d_inode, MAY_EXEC); + if (err) + goto exit; + + down_write(&mm->mmap_sem); + if (mm->num_exe_file_vmas) { + + err = deny_write_access(exe_file); + if (err) { + up_write(&mm->mmap_sem); + goto exit; + } + + fput(mm->exe_file); + mm->exe_file = exe_file; + } else { + fput(exe_file); + err = -ENXIO; + } + up_write(&mm->mmap_sem); + +exit: + return err; +} + static int prctl_set_mm(int opt, unsigned long addr, unsigned long arg4, unsigned long arg5) { @@ -1715,6 +1767,9 @@ 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 +1892,7 @@ static int prctl_set_mm(int opt, unsigne return 0; } + default: error = -EINVAL; goto out;