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[209.85.220.65]) by mx.google.com with SMTPS id x7sor5238187ybg.192.2019.07.02.03.45.44 for (Google Transport Security); Tue, 02 Jul 2019 03:45:44 -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="kdVby+/P"; 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=vlidC+hQ/gD/8v9eleM4nXtfiap8zhCG0j5qbLCVw18=; b=kdVby+/PzZu5i6Y9UcQYatHEHHsEPhAQY+mjVHF6xlggt8o+nszbdHXCHfEBil5H5H UL+/28eYKfUAOv8AvNzRMQHWK/y4MABFSamQhRwNZH1hpEc5BUQCjqITvhev6DLWRzG3 uOgpinFcBt7pSePpbwiWspS3cbj7dBXMod+4Z94YngJ+nIPc3qdhbsYftXAC3oBGhakE Bt+6iCjbrfqQEg0SzB1WdrzlyuHEb0JfhuYdop7KFU8fbo4QPvOCj4+Z+NVkWFYsg5RT IRHHoit1jxeDZWaJHULPmpdSPTutxwczS9nSE3h7MYk2MPhM/kHniCv9ovLGXWy3LfTv lmfQ== X-Google-Smtp-Source: APXvYqzMdrjXgWGhi/zPaZxEj+t8DhHrW56qP/YMhmryxOT2o02rqdhc3hQ5y4gjPvsnd8KwypjTK3Tgmn2Zfydvxjo= X-Received: by 2002:a25:8109:: with SMTP id o9mr16913558ybk.132.1562064343920; Tue, 02 Jul 2019 03:45:43 -0700 (PDT) MIME-Version: 1.0 References: <156174687561.1557469.7505651950825460767.stgit@magnolia> <156174690758.1557469.9258105121276292687.stgit@magnolia> <20190701154200.GK1404256@magnolia> In-Reply-To: <20190701154200.GK1404256@magnolia> From: Amir Goldstein Date: Tue, 2 Jul 2019 13:45:32 +0300 Message-ID: Subject: Re: [PATCH v2 4/4] vfs: don't allow most setxattr to immutable files To: "Darrick J. Wong" Cc: matthew.garrett@nebula.com, Chao Yu , Theodore Tso , Ard Biesheuvel , Josef Bacik , Christoph Hellwig , Chris Mason , Andreas Dilger , Al Viro , Jan Kara , David Sterba , Jaegeuk Kim , jk@ozlabs.org, reiserfs-devel@vger.kernel.org, linux-efi@vger.kernel.org, devel@lists.orangefs.org, linux-kernel , linux-f2fs-devel@lists.sourceforge.net, linux-xfs , Linux MM , linux-nilfs@vger.kernel.org, linux-mtd@lists.infradead.org, ocfs2-devel@oss.oracle.com, linux-fsdevel , Ext4 , Linux Btrfs 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 Mon, Jul 1, 2019 at 7:31 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 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 > --- > v2: use memcmp instead of open coding a bunch of checks Thanks, Reviewed-by: Amir Goldstein > --- > fs/inode.c | 17 +++++++++++++++++ > 1 file changed, 17 insertions(+) > > diff --git a/fs/inode.c b/fs/inode.c > index cf07378e5731..31f694e405fe 100644 > --- a/fs/inode.c > +++ b/fs/inode.c > @@ -2214,6 +2214,14 @@ int vfs_ioc_setflags_prepare(struct inode *inode, unsigned int oldflags, > !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) && > + oldflags != flags) > + return -EPERM; > + > /* > * Now that we're done checking the new flags, flush all pending IO and > * dirty mappings before setting S_IMMUTABLE on an inode via > @@ -2284,6 +2292,15 @@ int vfs_ioc_fssetxattr_check(struct inode *inode, const struct fsxattr *old_fa, > !(S_ISREG(inode->i_mode) || S_ISDIR(inode->i_mode))) > return -EINVAL; > > + /* > + * We aren't allowed to change any fields if the immutable flag is > + * already set and is not being unset. > + */ > + if ((old_fa->fsx_xflags & FS_XFLAG_IMMUTABLE) && > + (fa->fsx_xflags & FS_XFLAG_IMMUTABLE) && > + memcmp(fa, old_fa, offsetof(struct fsxattr, fsx_pad))) > + 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);