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Date:   Wed, 15 Jan 2020 10:21:45 +0000
From:   David Laight <David.Laight@...LAB.COM>
To:     "''" <>,
        "" <>
CC:     Alexander Viro <>,
        "Darrick J. Wong" <>,
        Dan Williams <>,
        "Dave Chinner" <>,
        Christoph Hellwig <>,
        "Theodore Y. Ts'o" <>, Jan Kara <>,
        "" <>,
        "" <>,
        "" <>
Subject: RE: [RFC PATCH V2 09/12] fs: Prevent mode change if file is mmap'ed

> Sent: 10 January 2020 19:30
> Page faults need to ensure the inode mode is correct and consistent with
> the vmf information at the time of the fault.  There is no easy way to
> ensure the vmf information is correct if a mode change is in progress.
> Furthermore, there is no good use case to require a mode change while
> the file is mmap'ed.
> Track mmap's of the file and fail the mode change if the file is
> mmap'ed.

This seems wrong to me.
I presume the 'mode changes' are from things like 'chmod -w ...'.
mmap() should be no different to open().
Only the permissions set when the file is opened count.

Next you'll be stopping unlink() when a file is open :-)


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