From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail.zytor.com (terminus.zytor.com [198.137.202.136]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 28C2619F489 for ; Tue, 12 Nov 2024 02:54:08 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=198.137.202.136 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1731380051; cv=none; b=kF/CnO9t13sHFFmkHzYYZim3mTsC4uquZvM3MG2ksaFUZ48qZmc9ES5tiIN1vJKY+o71REMDohEzUNXxriKIu0gRYcbfWSo4MToMf2ojxzX9XiqDh67rTVJRDFW1IXVjGyYdvpKIjNO1BUxzBREGgt1XZ9bj9G+y8iv2VP3stgg= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1731380051; c=relaxed/simple; bh=wlbvrhqyWyTvnCkoAxzxk1XF4fc0oJTGZ1qf5xAYkWY=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=D5NHmxTi8IrRr3lzOzFcMnQThDRqYDAopuklMWNUrC9iWaE1S3Ol58X/sGKvFEJ+Vs6v4ZO2uZjMUhMygEYFEX8btbM4iPsvmQwCSylPm0MRV/Wyz9L0GNlll3LAX5lsRk6t5E4+8MCRlBFk6m1vIP3fKDNKpzEBglMMiu1UEVI= ARC-Authentication-Results:i=1; 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h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=e3Bp+zDBUBc7t8gSWsAhOHpGiz0jxnlMUf3VfEm8JKCFYxBffzsXvcR9zQbzDk977 /m+F2GDcomvYNCAUaL6T15PQrHe2q92yDhWWekgLC95WqKi5JPdV05IxpCd7qZo6i7 Qu+wViP/q82NKcdfSip9eB35A568wGEClK74jAOEuu92gdIxunNtGmkQTHLKIGaT1u wXjRH0IBMJnsfFlqK/2wLG1jieL+rxE3V5D+HljOrd518oxkwjt8mWEwbtScnoNkEq MCNi67i2EMX6wZzFhUQZxmc3Ck+erSU94EejGbT+9/0UChcgRBS+4c4S6zNf7MKbOU prZ/TdGjVxpmA== Message-ID: <6735d24c-b031-499d-b298-ef8861b4daba@zytor.com> Date: Mon, 11 Nov 2024 18:53:09 -0800 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 1/1] x86/fred: Clear WFE in missing-ENDBRANCH #CPs To: Andrew Cooper , linux-kernel@vger.kernel.org Cc: tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, dave.hansen@linux.intel.com, x86@kernel.org, hpa@zytor.com, peterz@infradead.org References: <20240916181000.416513-1-xin@zytor.com> <49b6c23b-dfd8-4874-bd6e-998dd039ed1a@zytor.com> <473f9dae-b711-4d96-8804-209275b963a2@citrix.com> Content-Language: en-US From: Xin Li Autocrypt: addr=xin@zytor.com; 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charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 11/8/2024 12:53 PM, Andrew Cooper wrote: >> Andrew, >> >> can you please take another look? > After discussing with Dave on IRC, the ibt_clear_fred_wfe(regs); really > needs to be inside the ibt_selftest_noendbr path. > Sigh, I missed the discussion. > It's a selftest where we're deliberately trying to trigger #CP, and in > the one case where we're happy should we say "yeah, safe to clobber WFE > in the interrupted context" to let execution continue. > > Clobbering WFE in any other circumstance is a security-relevant bug. I think we also need to clear WFE when !ibt_fatal. No? diff --git a/arch/x86/kernel/cet.c b/arch/x86/kernel/cet.c index fb8f4238969e..69a34636811f 100644 --- a/arch/x86/kernel/cet.c +++ b/arch/x86/kernel/cet.c @@ -128,6 +128,7 @@ static void do_kernel_cp_fault(struct pt_regs *regs, unsigned long error_code) if (!ibt_fatal) { printk(KERN_DEFAULT CUT_HERE); __warn(__FILE__, __LINE__, (void *)regs->ip, TAINT_WARN, regs, NULL); + ibt_clear_fred_wfe(regs); return; } BUG();