linux-kernel - Re: [PATCH 1/2] drm/i915: Remove redundant user_access_end() from __copy_from

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Message-ID: <20190725202114.hxwnnu4sihus53ci@treble>
Date:   Thu, 25 Jul 2019 15:21:14 -0500
From:   Josh Poimboeuf <jpoimboe@...hat.com>
To:     Sedat Dilek <sedat.dilek@...il.com>
Cc:     x86@...nel.org, linux-kernel@...r.kernel.org,
        Peter Zijlstra <peterz@...radead.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Chris Wilson <chris@...is-wilson.co.uk>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Nathan Chancellor <natechancellor@...il.com>,
        Arnd Bergmann <arnd@...db.de>
Subject: Re: [PATCH 1/2] drm/i915: Remove redundant user_access_end() from
 __copy_from_user() error path

On Thu, Jul 25, 2019 at 08:10:49AM +0200, Sedat Dilek wrote:
> On Thu, Jul 25, 2019 at 12:48 AM Josh Poimboeuf <jpoimboe@...hat.com> wrote:
> >
> > Objtool reports:
> >
> >   drivers/gpu/drm/i915/gem/i915_gem_execbuffer.o: warning: objtool: .altinstr_replacement+0x36: redundant UACCESS disable
> >
> > __copy_from_user() already does both STAC and CLAC, so the
> > user_access_end() in its error path adds an extra unnecessary CLAC.
> >
> > Fixes: 0b2c8f8b6b0c ("i915: fix missing user_access_end() in page fault exception case")
> > Reported-by: Thomas Gleixner <tglx@...utronix.de>
> > Reported-by: Sedat Dilek <sedat.dilek@...il.com>
> > Acked-by: Peter Zijlstra (Intel) <peterz@...radead.org>
> > Tested-by: Nick Desaulniers <ndesaulniers@...gle.com>
> > Link: https://github.com/ClangBuiltLinux/linux/issues/617
> > Signed-off-by: Josh Poimboeuf <jpoimboe@...hat.com>
> 
> Just for the records and ensuing ages:
> 
> Tested-by: Sedat Dilek <sedat.dilek@...il.com>

Thanks Sedat.  Since the objtool fix already got merged separately I'll
resend this patch to the drm folks.

-- 
Josh