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    SubjectRe: [PATCH] Check for immutable flag in fallocate path
    Il 27/02/2011 23:49, Ted Ts'o ha scritto:
    > On Mon, Feb 21, 2011 at 05:50:21PM +0100, Marco Stornelli wrote:
    >> 2011/2/21 Christoph Hellwig <hch@infradead.org>:
    >>> 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.
    >>>
    >>>
    >>
    >> 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


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