Il 27/02/2011 23:49, Ted Ts'o ha scritto:

On Mon, Feb 21, 2011 at 05:50:21PM +0100, Marco Stornelli wrote:

quoted

2011/2/21 Christoph Hellwig [off-list ref]:

quoted

On Mon, Feb 21, 2011 at 09:26:32AM +0100, Marco Stornelli wrote:

quoted

From: Marco Stornelli <redacted>

All fs must check for the immutable flag in their fallocate callback.
It's possible to have a race condition in this scenario: an application
open a file in read/write and it does something, meanwhile root set the
immutable flag on the file, the application at that point can call
fallocate with success. Only Ocfs2 check for the immutable flag at the
moment.

Please add the check in fs/open.c:do_fallocate() so that it covers all
filesystems.

The check should be done after the fs got the inode mutex lock.

Why?  None of the other places which check the IMMUTABLE flag do so

I add to my previous response an other point: IMHO each fs should check
for it because after the inclusion of punch hole patch, the fs
can/cannot check for the append-only flag. So XFS (it supports the
"unreserve") should check even for append. I think we don't want to
allow this operation for an append-only file, isn't it? About this point
I'll update and resend my patch.

Marco