From: "Theodore Ts'o" <tytso@mit.edu>
To: "Darrick J. Wong" <darrick.wong@oracle.com>
Cc: linux-xfs@vger.kernel.org, linux-fsdevel@vger.kernel.org,
linux-ext4@vger.kernel.org, linux-btrfs@vger.kernel.org,
linux-mm@kvack.org
Subject: Re: [PATCH 1/8] mm/fs: don't allow writes to immutable files
Date: Sun, 9 Jun 2019 21:43:29 -0400 [thread overview]
Message-ID: <20190610014329.GA3266@mit.edu> (raw)
In-Reply-To: <155552787330.20411.11893581890744963309.stgit@magnolia>
On Wed, Apr 17, 2019 at 12:04:33PM -0700, Darrick J. Wong wrote:
> From: Darrick J. Wong <darrick.wong@oracle.com>
>
> 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."
>
> Once the flag is set, it is enforced for quite a few file operations,
> such as fallocate, fpunch, fzero, rm, touch, open, etc. However, we
> don't check for immutability when doing a write(), a PROT_WRITE mmap(),
> a truncate(), or a write to a previously established mmap.
>
> If a program has an open write fd to a file that the administrator
> subsequently marks immutable, the program still can change the file
> contents. Weird!
>
> The ability to write to an immutable file does not follow the manpage
> promise that immutable files cannot be modified. Worse yet it's
> inconsistent with the behavior of other syscalls which don't allow
> modifications of immutable files.
>
> Therefore, add the necessary checks to make the write, mmap, and
> truncate behavior consistent with what the manpage says and consistent
> with other syscalls on filesystems which support IMMUTABLE.
>
> Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Thanks, looks good. I'm going to take this patch through the ext4
tree since it doesn't have any dependencies on the rest of the patch
series.
- Ted
next prev parent reply other threads:[~2019-06-10 1:43 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-04-17 19:04 [PATCH v2 0/8] vfs: make immutable files actually immutable Darrick J. Wong
2019-04-17 19:04 ` [PATCH 1/8] mm/fs: don't allow writes to immutable files Darrick J. Wong
2019-04-26 18:17 ` Brian Foster
2019-06-10 1:43 ` Theodore Ts'o [this message]
2019-06-10 1:51 ` Theodore Ts'o
2019-06-10 4:41 ` Darrick J. Wong
2019-06-10 13:14 ` Theodore Ts'o
2019-06-10 16:09 ` Darrick J. Wong
2019-06-10 20:41 ` Theodore Ts'o
2019-06-11 3:26 ` Darrick J. Wong
2019-06-11 4:01 ` Darrick J. Wong
2019-04-17 19:04 ` [PATCH 2/8] xfs: unlock inode when xfs_ioctl_setattr_get_trans can't get transaction Darrick J. Wong
2019-04-26 18:17 ` Brian Foster
2019-04-17 19:04 ` [PATCH 3/8] xfs: flush page mappings as part of setting immutable Darrick J. Wong
2019-04-26 18:18 ` Brian Foster
2019-04-17 19:04 ` [PATCH 4/8] xfs: refactor setflags to use setattr code directly Darrick J. Wong
2019-04-17 19:05 ` [PATCH 5/8] xfs: clean up xfs_merge_ioc_xflags Darrick J. Wong
2019-04-17 19:05 ` [PATCH 6/8] xfs: don't allow most setxattr to immutable files Darrick J. Wong
2019-04-17 19:05 ` [PATCH 7/8] btrfs: don't allow any modifications to an immutable file Darrick J. Wong
2019-04-17 19:05 ` [PATCH 8/8] ext4: " Darrick J. Wong
2019-04-30 15:46 ` [PATCH v2 0/8] vfs: make immutable files actually immutable David Sterba
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