[Cluster-devel] [PATCH] Check for immutable flag in fallocate path

[Cluster-devel] [PATCH] Check for immutable flag in fallocate path

[Christoph Hellwig]

On Mon, Feb 21, 2011 at 09:26:32AM +0100, Marco Stornelli wrote:
> From: Marco Stornelli <marco.stornelli@gmail.com>
> 
> 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.

[Cluster-devel] [PATCH v2] Check for immutable flag in fallocate path

[Christoph Hellwig]

On Fri, Mar 04, 2011 at 08:39:03AM +1100, Dave Chinner wrote:
> WTF?  Why does append mode have any effect on whether we can punch
> holes in a file or not? There's no justification for adding this in
> the commit message. Why is it even in a patch that is for checking
> immutable inodes? What is the point of adding it, when all that will
> happen is people will switch to XFS_IOC_UNRESVSP which has never had
> this limitation?

xfs_ioc_space unconditionally rejects inodes with S_APPEND set for
all preallocation / hole punching ioctls.  This might be overzealous for
preallocations not changing the size, or just extending i_size, but it's
IMHO entirely correct for hole punching.