Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752442Ab3F3BQS (ORCPT ); Sat, 29 Jun 2013 21:16:18 -0400 Received: from out01.mta.xmission.com ([166.70.13.231]:57419 "EHLO out01.mta.xmission.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751027Ab3F3BQQ (ORCPT ); Sat, 29 Jun 2013 21:16:16 -0400 From: ebiederm@xmission.com (Eric W. Biederman) To: Rob Landley Cc: linux-kernel@vger.kernel.org, Al Viro References: <1372536729.850656@landley.net> Date: Sat, 29 Jun 2013 18:15:40 -0700 In-Reply-To: <1372536729.850656@landley.net> (Rob Landley's message of "Sat, 29 Jun 2013 13:12:14 -0700 (PDT)") Message-ID: <87y59swg8z.fsf@xmission.com> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/24.1 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain X-XM-AID: U2FsdGVkX1+zxUciEgJl6ax4laeDH3yPgsXXrU5Mi30= X-SA-Exim-Connect-IP: 98.207.154.105 X-SA-Exim-Mail-From: ebiederm@xmission.com X-Spam-Report: * -1.0 ALL_TRUSTED Passed through trusted hosts only via SMTP * 1.5 XMNoVowels Alpha-numberic number with no vowels * 0.0 T_TM2_M_HEADER_IN_MSG BODY: T_TM2_M_HEADER_IN_MSG * -3.0 BAYES_00 BODY: Bayes spam probability is 0 to 1% * [score: 0.0000] * -0.0 DCC_CHECK_NEGATIVE Not listed in DCC * [sa07 1397; Body=1 Fuz1=1 Fuz2=1] * 0.0 T_TooManySym_01 4+ unique symbols in subject X-Spam-DCC: XMission; sa07 1397; Body=1 Fuz1=1 Fuz2=1 X-Spam-Combo: ;Rob Landley X-Spam-Relay-Country: Subject: Re: [PATCH 1/5] initmpfs: replace MS_NOUSER in initramfs X-Spam-Flag: No X-SA-Exim-Version: 4.2.1 (built Wed, 14 Nov 2012 14:26:46 -0700) X-SA-Exim-Scanned: Yes (on in02.mta.xmission.com) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1533 Lines: 47 Rob Landley writes: > From: Rob Landley > > Mounting MS_NOUSER prevents --bind mounts from rootfs. Prevent new rootfs > mounts with a different mechanism that doesn't affect bind mounts. I don't see patches 4 and 5 so I don't know if you have covered this elsewhere but a very important part of the reason for MS_NOUSER is to prevent unmounting of rootfs. The entire vfs breaks if you are allowed to unmount rootfs, and it appears this patch is allowing that. Eric > Signed-off-by: Rob Landley > --- > > fs/ramfs/inode.c | 9 ++++++++- > 1 file changed, 8 insertions(+), 1 deletion(-) > > diff --git a/fs/ramfs/inode.c b/fs/ramfs/inode.c > index c24f1e1..14b9c35 100644 > --- a/fs/ramfs/inode.c > +++ b/fs/ramfs/inode.c > @@ -247,7 +247,14 @@ struct dentry *ramfs_mount(struct file_system_type *fs_type, > static struct dentry *rootfs_mount(struct file_system_type *fs_type, > int flags, const char *dev_name, void *data) > { > - return mount_nodev(fs_type, flags|MS_NOUSER, data, ramfs_fill_super); > + static int once; > + > + if (once) > + return ERR_PTR(-ENODEV); > + else > + once++; > + > + return mount_nodev(fs_type, flags, data, ramfs_fill_super); > } > > static void ramfs_kill_sb(struct super_block *sb) -- 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/