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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
From: Ben Hutchings <ben.hutchings@codethink.co.uk>
To: Eric Biggers <ebiggers3@gmail.com>
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Date: Mon, 16 Oct 2017 18:55:06 +0100
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On Mon, 2017-10-16 at 10:52 -0700, Eric Biggers wrote:
> 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.

I missed that.  Thanks.

Ben.

-- 
Ben Hutchings
Software Developer, Codethink Ltd.