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[209.85.220.65]) by mx.google.com with SMTPS id a4sor39633ywh.4.2019.03.28.14.24.59 for (Google Transport Security); Thu, 28 Mar 2019 14:24:59 -0700 (PDT) Received-SPF: pass (google.com: domain of amir73il@gmail.com designates 209.85.220.65 as permitted sender) client-ip=209.85.220.65; Authentication-Results: mx.google.com; dkim=pass header.i=@gmail.com header.s=20161025 header.b=k5fGldQp; spf=pass (google.com: domain of amir73il@gmail.com designates 209.85.220.65 as permitted sender) smtp.mailfrom=amir73il@gmail.com; dmarc=pass (p=NONE sp=QUARANTINE dis=NONE) header.from=gmail.com DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=+5hDRqCC4Yz7e19xR7ypxPfWKLZ6F+sf7ORQmgcR9Ps=; b=k5fGldQpVI0bwsgIZNr9pXognzOfQvw5xFDhUL7N+zK6kdMbOoGBjgvosPG29RWwLi lw29EFJqYdKmc6UHgxTRSvab4ooaaBXrtxJIklUQx+K36ExLyoD+O+Kc4ydeRy5T5lTI btB6Q51tBV5SLbomzbqjtuhO+exQ8c1ArjLZRFvyoFxh9syQSV1vnMIKA1IT3AdcWMOK NNqQ6gflcs2/UtDzHP2D/RQj5YcLQCvR+NB4mnPmHqXj9AYZjkRdbM+Jez2Xw3HZXn8h NCKI7RKUVTQ9xmN4h83TKgVt8ekc/AGflRYCC8phl2G1czt1AtwjA7pBn4PtSaqFIB4c 4AbA== X-Google-Smtp-Source: APXvYqwYYXQujvgO0SGJ/j2p6/WWoKZg2i6iM5EpYPfHmNXAa0l+VqisTK4JaZddN4+LHCMHdLa+l5R5TpIE7qfdepY= X-Received: by 2002:a0d:e252:: with SMTP id l79mr36846886ywe.248.1553808299501; Thu, 28 Mar 2019 14:24:59 -0700 (PDT) MIME-Version: 1.0 References: <155379543409.24796.5783716624820175068.stgit@magnolia> <155379545404.24796.5019142212767521955.stgit@magnolia> In-Reply-To: <155379545404.24796.5019142212767521955.stgit@magnolia> From: Amir Goldstein Date: Thu, 28 Mar 2019 23:24:48 +0200 Message-ID: Subject: Re: [PATCH 3/3] xfs: don't allow most setxattr to immutable files To: "Darrick J. Wong" Cc: linux-xfs , linux-fsdevel , Ext4 , Linux Btrfs , Linux MM Content-Type: text/plain; charset="UTF-8" X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Thu, Mar 28, 2019 at 7:51 PM 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 project ids and extent size hints on > supposedly immutable files. Therefore, reject a setattr call on an > immutable file except for the case where we're trying to unset > IMMUTABLE. > I think if preventing modification of projid and extent size hints is what you are after you should place the check in xfs_ioctl_setattr() and not in xfs_ioctl_setattr_xflags(). Yes, it sounds tempting to block changes of xfs_ioc_setxflags(), but it leads you to a trap of 2nd time chattr +i fails on -EPERM, because chattr(1) doesn't optimize out the SETFLAGS ioctl in the case of unmodified flags. I think if you try to fix that, code will get ugly, so I suggest that you let SETFLAGS slide. Thanks, Amir. > Signed-off-by: Darrick J. Wong > --- > fs/xfs/xfs_ioctl.c | 8 ++++++++ > 1 file changed, 8 insertions(+) > > > diff --git a/fs/xfs/xfs_ioctl.c b/fs/xfs/xfs_ioctl.c > index 2bd1c5ab5008..9cf0bc0ae2bd 100644 > --- a/fs/xfs/xfs_ioctl.c > +++ b/fs/xfs/xfs_ioctl.c > @@ -1067,6 +1067,14 @@ xfs_ioctl_setattr_xflags( > !capable(CAP_LINUX_IMMUTABLE)) > return -EPERM; > > + /* > + * If immutable is set and we are not clearing it, we're not allowed > + * to change anything else in the inode. > + */ > + if ((ip->i_d.di_flags & XFS_DIFLAG_IMMUTABLE) && > + (fa->fsx_xflags & FS_XFLAG_IMMUTABLE)) > + return -EPERM; > + > /* diflags2 only valid for v3 inodes. */ > di_flags2 = xfs_flags2diflags2(ip, fa->fsx_xflags); > if (di_flags2 && ip->i_d.di_version < 3) >