From: "Darrick J. Wong" <darrick.wong@oracle.com>
To: matthew.garrett@nebula.com, yuchao0@huawei.com, tytso@mit.edu,
darrick.wong@oracle.com, 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
Cc: 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
Subject: [PATCH v3 0/6] vfs: make immutable files actually immutable
Date: Mon, 10 Jun 2019 21:46:09 -0700 [thread overview]
Message-ID: <156022836912.3227213.13598042497272336695.stgit@magnolia> (raw)
Hi all,
The chattr(1) manpage has this to say about the immutable bit that
system administrators can set on 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."
Given the clause about how the file 'cannot be modified', it is
surprising that programs holding writable file descriptors can continue
to write to and truncate files after the immutable flag has been set,
but they cannot call other things such as utimes, fallocate, unlink,
link, setxattr, or reflink.
Since the immutable flag is only settable by administrators, resolve
this inconsistent behavior in favor of the documented behavior -- once
the flag is set, the file cannot be modified, period. We presume that
administrators must be trusted to know what they're doing, and that
cutting off programs with writable fds will probably break them.
Therefore, add immutability checks to the relevant VFS functions, then
refactor the SETFLAGS and FSSETXATTR implementations to use common
argument checking functions so that we can then force pagefaults on all
the file data when setting immutability.
Note that various distro manpages points out the inconsistent behavior
of the various Linux filesystems w.r.t. immutable. This fixes all that.
If you're going to start using this mess, you probably ought to just
pull from my git trees, which are linked below.
This has been lightly tested with fstests. Enjoy!
Comments and questions are, as always, welcome.
--D
kernel git tree:
https://git.kernel.org/cgit/linux/kernel/git/djwong/xfs-linux.git/log/?h=immutable-files
fstests git tree:
https://git.kernel.org/cgit/linux/kernel/git/djwong/xfstests-dev.git/log/?h=immutable-files
next reply other threads:[~2019-06-11 4:47 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-06-11 4:46 Darrick J. Wong [this message]
2019-06-11 4:46 ` [PATCH 1/6] mm/fs: don't allow writes to immutable files Darrick J. Wong
2019-06-20 21:52 ` Theodore Ts'o
2019-06-20 22:13 ` Darrick J. Wong
2019-06-21 0:54 ` Theodore Ts'o
2019-06-11 4:46 ` [PATCH 2/6] vfs: flush and wait for io when setting the immutable flag via SETFLAGS Darrick J. Wong
2019-06-20 14:00 ` Jan Kara
2019-06-20 22:09 ` Darrick J. Wong
2019-06-11 4:46 ` [PATCH 3/6] vfs: flush and wait for io when setting the immutable flag via FSSETXATTR Darrick J. Wong
2019-06-11 4:46 ` [PATCH 4/6] vfs: don't allow most setxattr to immutable files Darrick J. Wong
2019-06-20 14:03 ` Jan Kara
2019-06-20 21:36 ` Darrick J. Wong
2019-06-11 4:46 ` [PATCH 5/6] xfs: refactor setflags to use setattr code directly Darrick J. Wong
2019-06-11 4:47 ` [PATCH 6/6] xfs: clean up xfs_merge_ioc_xflags Darrick J. Wong
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