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Date:   Sun, 08 Jan 2017 10:03:09 -0500
From:   Mimi Zohar <>
To:     Christoph Hellwig <>
Cc:, Dave Chinner <>,
        linux-fsdevel <>,
        linux-kernel <>,
        Al Viro <>
Subject: Re: xfs:  commit 6552321831dc "xfs: remove i_iolock and use    i_rwsem
 in the VFS inode instead"  change causes hang

On Sun, 2017-01-08 at 15:52 +0100, Christoph Hellwig wrote:
> On Sun, Jan 08, 2017 at 09:48:44AM -0500, Mimi Zohar wrote:
> > IMA takes the i_rwsem (fomerly i_mutex) before reading the file to
> > synchronize calculating the file hash and validating the file's
> > hash/signature stored as security.ima xattr
> Well, it shouldn't do that.  In the I/O path i_rwsem is up to the
> fs to use.  Various other file systems also take it internally for
> reads, although mostly only for direct I/O.

But not normally for a normal file read.  For direct I/O, IMA fails the
file hash/signature verification, measurement, audit unless the IMA
"permit_directio" rule is defined.

> So the answer here is that ima needs to stop playing with i_rwsem.

Unless something has changed recently, to synchronize reading files to
calculate the file hash and writing xattrs it has to take the i_rwsem
prior to reading the file.


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