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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 44612CDB465 for ; Mon, 16 Oct 2023 08:51:11 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230017AbjJPIvK (ORCPT ); Mon, 16 Oct 2023 04:51:10 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:56630 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232982AbjJPIvJ (ORCPT ); Mon, 16 Oct 2023 04:51:09 -0400 Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id D67D6E3 for ; Mon, 16 Oct 2023 01:51:06 -0700 (PDT) Received: by smtp.kernel.org (Postfix) with ESMTPSA id D1D31C433C7; Mon, 16 Oct 2023 08:51:05 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1697446266; bh=fKu2ve04M7Fj5S3UWheCamY9z+JCuonuFplNMnFGywE=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=ufUL7/xisLbo08p7Xbd9ynPQRxQbe+03R9HsivDPSIs458rtu6rqe4MOO3j7JDnUe IPDoRX/Mub+LjbafJjwQsXxDnaQszoPPHsKlY+iePdUUDx41SziKwNaRtvdbc2jpO9 tJjuUeSo4dmZoR3udGTEBb7GmPyF76qaziBzl7pw= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Fei Yang , "Kirill A. Shutemov" , Ingo Molnar , "Peter Zijlstra (Intel)" , Linus Torvalds Subject: [PATCH 5.15 080/102] x86/alternatives: Disable KASAN in apply_alternatives() Date: Mon, 16 Oct 2023 10:41:19 +0200 Message-ID: <20231016083955.828521823@linuxfoundation.org> X-Mailer: git-send-email 2.42.0 In-Reply-To: <20231016083953.689300946@linuxfoundation.org> References: <20231016083953.689300946@linuxfoundation.org> User-Agent: quilt/0.67 X-stable: review X-Patchwork-Hint: ignore MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org 5.15-stable review patch. If anyone has any objections, please let me know. ------------------ From: Kirill A. Shutemov commit d35652a5fc9944784f6f50a5c979518ff8dacf61 upstream. Fei has reported that KASAN triggers during apply_alternatives() on a 5-level paging machine: BUG: KASAN: out-of-bounds in rcu_is_watching() Read of size 4 at addr ff110003ee6419a0 by task swapper/0/0 ... __asan_load4() rcu_is_watching() trace_hardirqs_on() text_poke_early() apply_alternatives() ... On machines with 5-level paging, cpu_feature_enabled(X86_FEATURE_LA57) gets patched. It includes KASAN code, where KASAN_SHADOW_START depends on __VIRTUAL_MASK_SHIFT, which is defined with cpu_feature_enabled(). KASAN gets confused when apply_alternatives() patches the KASAN_SHADOW_START users. A test patch that makes KASAN_SHADOW_START static, by replacing __VIRTUAL_MASK_SHIFT with 56, works around the issue. Fix it for real by disabling KASAN while the kernel is patching alternatives. [ mingo: updated the changelog ] Fixes: 6657fca06e3f ("x86/mm: Allow to boot without LA57 if CONFIG_X86_5LEVEL=y") Reported-by: Fei Yang Signed-off-by: Kirill A. Shutemov Signed-off-by: Ingo Molnar Acked-by: Peter Zijlstra (Intel) Cc: Linus Torvalds Cc: stable@vger.kernel.org Link: https://lore.kernel.org/r/20231012100424.1456-1-kirill.shutemov@linux.intel.com Signed-off-by: Kirill A. Shutemov Signed-off-by: Greg Kroah-Hartman --- arch/x86/kernel/alternative.c | 13 +++++++++++++ 1 file changed, 13 insertions(+) --- a/arch/x86/kernel/alternative.c +++ b/arch/x86/kernel/alternative.c @@ -269,6 +269,17 @@ void __init_or_module noinline apply_alt u8 insn_buff[MAX_PATCH_LEN]; DPRINTK("alt table %px, -> %px", start, end); + + /* + * In the case CONFIG_X86_5LEVEL=y, KASAN_SHADOW_START is defined using + * cpu_feature_enabled(X86_FEATURE_LA57) and is therefore patched here. + * During the process, KASAN becomes confused seeing partial LA57 + * conversion and triggers a false-positive out-of-bound report. + * + * Disable KASAN until the patching is complete. + */ + kasan_disable_current(); + /* * The scan order should be from start to end. A later scanned * alternative code can overwrite previously scanned alternative code. @@ -336,6 +347,8 @@ void __init_or_module noinline apply_alt next: optimize_nops(instr, a->instrlen); } + + kasan_enable_current(); } #if defined(CONFIG_RETPOLINE) && defined(CONFIG_STACK_VALIDATION)