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Date: Mon, 16 Oct 2017 10:52:02 -0700
From: Eric Biggers <ebiggers3@gmail.com>
To: Ben Hutchings <ben.hutchings@codethink.co.uk>
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Subject: Re: Patch "x86/fpu: Don't let userspace set bogus xcomp_bv" has been
 added to the 4.4-stable tree
Message-ID: <20171016175202.GB121701@gmail.com>
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 <1508175292.22379.30.camel@codethink.co.uk>
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Hi Ben,

On Mon, Oct 16, 2017 at 06:34:52PM +0100, Ben Hutchings wrote:
> On Mon, 2017-10-02 at 20:59 +0200, gregkh@linuxfoundation.org wrote:
> [...]
> > From: Eric Biggers <ebiggers@google.com>
> > 
> > commit 814fb7bb7db5433757d76f4c4502c96fc53b0b5e upstream.
> > 
> > [Please apply to 4.4-stable.��Note: the backport includes the
> > fpstate_init() call in xstateregs_set(), since fix is useless without
> > it.��It was added by commit 91c3dba7dbc1 ("x86/fpu/xstate: Fix PTRACE
> > frames for XSAVES"), but it doesn't make sense to backport that whole
> > commit.]
> [...]
> 
> Why doesn't it make sense to backport that?  It seems less important
> than this fix, but it fixes a userspace-visible regression.
> 

It seems that commit was part of a series of commits that fixed XSAVES support
and then re-enabled it.  Before then the XSAVES support was actually disabled;
see commit e88221c50cad ("x86/fpu: Disable XSAVES* support for now").  So commit
91c3dba7dbc1 didn't fix a regression, as the code was already disabled.

Eric