From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-8.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id BD583C433DF for ; Mon, 6 Jul 2020 15:22:24 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 9F52F206CD for ; Mon, 6 Jul 2020 15:22:24 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729403AbgGFPWX (ORCPT ); Mon, 6 Jul 2020 11:22:23 -0400 Received: from foss.arm.com ([217.140.110.172]:49078 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729197AbgGFPWX (ORCPT ); Mon, 6 Jul 2020 11:22:23 -0400 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 42D44C0A; Mon, 6 Jul 2020 08:22:22 -0700 (PDT) Received: from lakrids.cambridge.arm.com (usa-sjc-imap-foss1.foss.arm.com [10.121.207.14]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 1987A3F71E; Mon, 6 Jul 2020 08:22:20 -0700 (PDT) Date: Mon, 6 Jul 2020 16:21:53 +0100 From: Mark Rutland To: Vincenzo Frascino Cc: kasan-dev@googlegroups.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org, Andrey Ryabinin , Alexander Potapenko , Dmitry Vyukov , Andrew Morton Subject: Re: [PATCH] kasan: Remove kasan_unpoison_stack_above_sp_to() Message-ID: <20200706152152.GA45787@lakrids.cambridge.arm.com> References: <20200706143505.23299-1-vincenzo.frascino@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200706143505.23299-1-vincenzo.frascino@arm.com> User-Agent: Mutt/1.11.1+11 (2f07cb52) (2018-12-01) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Jul 06, 2020 at 03:35:05PM +0100, Vincenzo Frascino wrote: > The function kasan_unpoison_stack_above_sp_to() is defined in kasan code > but never used. The function was introduced as part of the commit: > > commit 9f7d416c36124667 ("kprobes: Unpoison stack in jprobe_return() for KASAN") > > ... where it was necessary because x86's jprobe_return() would leave > stale shadow on the stack, and was an oddity in that regard. > > Since then, jprobes were removed entirely, and as of commit: > > commit 80006dbee674f9fa ("kprobes/x86: Remove jprobe implementation") > > ... there have been no callers of this function. > > Remove the declaration and the implementation. > > Cc: Andrey Ryabinin > Cc: Alexander Potapenko > Cc: Dmitry Vyukov > Cc: Andrew Morton > Signed-off-by: Vincenzo Frascino This looks sane to me, and I'm not aware of any cases oputside of jprobes that would need this, so FWIW: Reviewed-by: Mark Rutland Mark. > --- > include/linux/kasan.h | 2 -- > mm/kasan/common.c | 15 --------------- > 2 files changed, 17 deletions(-) > > diff --git a/include/linux/kasan.h b/include/linux/kasan.h > index 82522e996c76..0ebf2fab8567 100644 > --- a/include/linux/kasan.h > +++ b/include/linux/kasan.h > @@ -38,7 +38,6 @@ extern void kasan_disable_current(void); > void kasan_unpoison_shadow(const void *address, size_t size); > > void kasan_unpoison_task_stack(struct task_struct *task); > -void kasan_unpoison_stack_above_sp_to(const void *watermark); > > void kasan_alloc_pages(struct page *page, unsigned int order); > void kasan_free_pages(struct page *page, unsigned int order); > @@ -101,7 +100,6 @@ void kasan_restore_multi_shot(bool enabled); > static inline void kasan_unpoison_shadow(const void *address, size_t size) {} > > static inline void kasan_unpoison_task_stack(struct task_struct *task) {} > -static inline void kasan_unpoison_stack_above_sp_to(const void *watermark) {} > > static inline void kasan_enable_current(void) {} > static inline void kasan_disable_current(void) {} > diff --git a/mm/kasan/common.c b/mm/kasan/common.c > index 757d4074fe28..6339179badb2 100644 > --- a/mm/kasan/common.c > +++ b/mm/kasan/common.c > @@ -180,21 +180,6 @@ asmlinkage void kasan_unpoison_task_stack_below(const void *watermark) > kasan_unpoison_shadow(base, watermark - base); > } > > -/* > - * Clear all poison for the region between the current SP and a provided > - * watermark value, as is sometimes required prior to hand-crafted asm function > - * returns in the middle of functions. > - */ > -void kasan_unpoison_stack_above_sp_to(const void *watermark) > -{ > - const void *sp = __builtin_frame_address(0); > - size_t size = watermark - sp; > - > - if (WARN_ON(sp > watermark)) > - return; > - kasan_unpoison_shadow(sp, size); > -} > - > void kasan_alloc_pages(struct page *page, unsigned int order) > { > u8 tag; > -- > 2.27.0 >