From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx2.suse.de ([195.135.220.15]:49182 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726551AbfFTODs (ORCPT ); Thu, 20 Jun 2019 10:03:48 -0400 Date: Thu, 20 Jun 2019 16:03:45 +0200 From: Jan Kara Subject: Re: [PATCH 4/6] vfs: don't allow most setxattr to immutable files Message-ID: <20190620140345.GI30243@quack2.suse.cz> References: <156022836912.3227213.13598042497272336695.stgit@magnolia> <156022840560.3227213.4776913678782966728.stgit@magnolia> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <156022840560.3227213.4776913678782966728.stgit@magnolia> Sender: linux-xfs-owner@vger.kernel.org List-ID: List-Id: xfs To: "Darrick J. Wong" Cc: matthew.garrett@nebula.com, yuchao0@huawei.com, tytso@mit.edu, ard.biesheuvel@linaro.org, josef@toxicpanda.com, clm@fb.com, adilger.kernel@dilger.ca, viro@zeniv.linux.org.uk, jack@suse.com, dsterba@suse.com, jaegeuk@kernel.org, jk@ozlabs.org, reiserfs-devel@vger.kernel.org, linux-efi@vger.kernel.org, devel@lists.orangefs.org, linux-kernel@vger.kernel.org, linux-f2fs-devel@lists.sourceforge.net, linux-xfs@vger.kernel.org, linux-mm@kvack.org, linux-nilfs@vger.kernel.org, linux-mtd@lists.infradead.org, ocfs2-devel@oss.oracle.com, linux-fsdevel@vger.kernel.org, linux-ext4@vger.kernel.org, linux-btrfs@vger.kernel.org On Mon 10-06-19 21:46:45, Darrick J. Wong wrote: > From: Darrick J. Wong > > The chattr manpage has this to say about immutable files: > > "A file with the 'i' attribute cannot be modified: it cannot be deleted > or renamed, no link can be created to this file, most of the file's > metadata can not be modified, and the file can not be opened in write > mode." > > However, we don't actually check the immutable flag in the setattr code, > which means that we can update inode flags and project ids and extent > size hints on supposedly immutable files. Therefore, reject setflags > and fssetxattr calls on an immutable file if the file is immutable and > will remain that way. > > Signed-off-by: Darrick J. Wong > --- > fs/inode.c | 31 +++++++++++++++++++++++++++++++ > 1 file changed, 31 insertions(+) > > > diff --git a/fs/inode.c b/fs/inode.c > index a3757051fd55..adfb458bf533 100644 > --- a/fs/inode.c > +++ b/fs/inode.c > @@ -2184,6 +2184,17 @@ int vfs_ioc_setflags_check(struct inode *inode, int oldflags, int flags) > !capable(CAP_LINUX_IMMUTABLE)) > return -EPERM; > > + /* > + * We aren't allowed to change any other flags if the immutable flag is > + * already set and is not being unset. > + */ > + if ((oldflags & FS_IMMUTABLE_FL) && > + (flags & FS_IMMUTABLE_FL)) { > + if ((oldflags & ~FS_IMMUTABLE_FL) != > + (flags & ~FS_IMMUTABLE_FL)) This check looks a bit strange when you've just check FS_IMMUTABLE_FL isn't changing... Why not just oldflags != flags? > + if ((old_fa->fsx_xflags & FS_XFLAG_IMMUTABLE) && > + (fa->fsx_xflags & FS_XFLAG_IMMUTABLE)) { > + if ((old_fa->fsx_xflags & ~FS_XFLAG_IMMUTABLE) != > + (fa->fsx_xflags & ~FS_XFLAG_IMMUTABLE)) Ditto here... > + return -EPERM; > + if (old_fa->fsx_projid != fa->fsx_projid) > + return -EPERM; > + if ((fa->fsx_xflags & (FS_XFLAG_EXTSIZE | > + FS_XFLAG_EXTSZINHERIT)) && > + old_fa->fsx_extsize != fa->fsx_extsize) > + return -EPERM; > + if ((old_fa->fsx_xflags & FS_XFLAG_COWEXTSIZE) && > + old_fa->fsx_cowextsize != fa->fsx_cowextsize) > + return -EPERM; > + } > + > /* Extent size hints of zero turn off the flags. */ > if (fa->fsx_extsize == 0) > fa->fsx_xflags &= ~(FS_XFLAG_EXTSIZE | FS_XFLAG_EXTSZINHERIT); Honza -- Jan Kara SUSE Labs, CR