From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Darrick J. Wong" Subject: Re: [PATCH 4/6] vfs: don't allow most setxattr to immutable files Date: Thu, 20 Jun 2019 14:36:29 -0700 Message-ID: <20190620213629.GB5375@magnolia> References: <156022836912.3227213.13598042497272336695.stgit@magnolia> <156022840560.3227213.4776913678782966728.stgit@magnolia> <20190620140345.GI30243@quack2.suse.cz> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=oracle.com; h=date : from : to : message-id : references : mime-version : in-reply-to : cc : subject : list-id : list-unsubscribe : list-archive : list-post : list-help : list-subscribe : content-type : content-transfer-encoding : sender; s=corp-2018-07-02; bh=MRDeE/if/9gyCkDUzf4q3uU1bqQ5tlis5p1XRL9HdpI=; b=lWOgzGeXzj8vRkk8H7gn1xr9qOLQCmtMwAki+bfbhHLO0YhLb3PLQewBjbM/hh8hcQqv LrZNVAOqKkeG85Bl1iccSiu3tcYQyAUztasn7ebaKA7CwI+6qhzfsInD+aAS73ctlBJ8 +Ve6A7gjCYFQcoSDj25sZBq+IjmUeG8v38H0bMPZ1kOxWEYWqSyTGkveKdwOGPyj6WmX RwyIcIZAfxYi4q9VPJbXjppt6CE1ojCVHz7bcVk9RvIU4pFdgaXfd7R6iT1kNyPReuL9 TDc9+9id4Draw7H7nuLk3Psxv5n29MOo+gN/gze3KBbboPG2ANgD2NWzMrhMC/RHkARg lw== Content-Disposition: inline In-Reply-To: <20190620140345.GI30243@quack2.suse.cz> List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: ocfs2-devel-bounces@oss.oracle.com Errors-To: ocfs2-devel-bounces@oss.oracle.com To: Jan Kara Cc: linux-efi@vger.kernel.org, linux-btrfs@vger.kernel.org, yuchao0@huawei.com, linux-mm@kvack.org, clm@fb.com, adilger.kernel@dilger.ca, matthew.garrett@nebula.com, linux-nilfs@vger.kernel.org, linux-ext4@vger.kernel.org, devel@lists.orangefs.org, josef@toxicpanda.com, reiserfs-devel@vger.kernel.org, viro@zeniv.linux.org.uk, dsterba@suse.com, jaegeuk@kernel.org, tytso@mit.edu, ard.biesheuvel@linaro.org, linux-kernel@vger.kernel.org, linux-f2fs-devel@lists.sourceforge.net, linux-xfs@vger.kernel.org, jk@ozlabs.org, jack@suse.com, linux-fsdevel@vger.kernel.org, linux-mtd@lists.infradead.org, ocfs2-devel@oss.oracle.com On Thu, Jun 20, 2019 at 04:03:45PM +0200, Jan Kara wrote: > 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... Good point! I'll fix it. --D > > > + 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