From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 B233A2EBDCC; Tue, 17 Jun 2025 15:41:26 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1750174886; cv=none; b=ST1n5ejqojj7o2Mk/KCwDDeBsGJBaiSygd/3lQEKs1CyX6hDX9H+WDqd8xpw8m2x82nVaMX0dbSXd+oF3f6GwPI6lcOrahfYExFG7s88dwB0kfGQ63qA7/E2fl2gKW062+8L9mFsfCr487c8BLTLx0tSEnD6RjlqfRKTtsWMPrs= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1750174886; c=relaxed/simple; bh=oowcxXkBPCRlRaRHiwVcI1Mi/UQ5rBmhOTN+MY7rGDI=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=WpBfAaz7+7P6lvPyU3pgs+G/I6TlC/zlAqy951BU+l0DZk9mddQMmRVvoc0CF7Ux0saLpm2mP2/8UmNZAPkt1GtNcRH3tdlbs1bh6trsgXr2YuUll0erPuhwDPjbcJMqUNdroebCVq6bfaM6/aCKfwGrUYsnGbuBkyl1OU2i55A= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=rQm9RG+Y; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="rQm9RG+Y" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 2A7B8C4CEF0; Tue, 17 Jun 2025 15:41:26 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1750174886; bh=oowcxXkBPCRlRaRHiwVcI1Mi/UQ5rBmhOTN+MY7rGDI=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=rQm9RG+Y7OEwT+t5ZeZW4p8F+psSRPh458I3QOQL/TSLayibsNExtvLVKDH2L5L2W Fxb7Z6FBTH5u9ONJNtIaHAMA9pvLvB+EUb5MhDsL7fViQs4d7ey7DAQye1oelZNbFt dfiC7UCLWJBnSfWwyLdgJhXYvJb7krKREnpe1k2o= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, "Ahmed S. Darwish" , Ingo Molnar , Andrew Cooper , "H. Peter Anvin" , John Ogness , x86-cpuid@lists.linux.dev, Sasha Levin Subject: [PATCH 6.15 030/780] x86/cpu: Sanitize CPUID(0x80000000) output Date: Tue, 17 Jun 2025 17:15:38 +0200 Message-ID: <20250617152452.731151133@linuxfoundation.org> X-Mailer: git-send-email 2.49.0 In-Reply-To: <20250617152451.485330293@linuxfoundation.org> References: <20250617152451.485330293@linuxfoundation.org> User-Agent: quilt/0.68 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.15-stable review patch. If anyone has any objections, please let me know. ------------------ From: Ahmed S. Darwish [ Upstream commit cc663ba3fe383a628a812f893cc98aafff39ab04 ] CPUID(0x80000000).EAX returns the max extended CPUID leaf available. On x86-32 machines without an extended CPUID range, a CPUID(0x80000000) query will just repeat the output of the last valid standard CPUID leaf on the CPU; i.e., a garbage values. Current tip:x86/cpu code protects against this by doing: eax = cpuid_eax(0x80000000); c->extended_cpuid_level = eax; if ((eax & 0xffff0000) == 0x80000000) { // CPU has an extended CPUID range. Check for 0x80000001 if (eax >= 0x80000001) { cpuid(0x80000001, ...); } } This is correct so far. Afterwards though, the same possibly broken EAX value is used to check the availability of other extended CPUID leaves: if (c->extended_cpuid_level >= 0x80000007) ... if (c->extended_cpuid_level >= 0x80000008) ... if (c->extended_cpuid_level >= 0x8000000a) ... if (c->extended_cpuid_level >= 0x8000001f) ... which is invalid. Fix this by immediately setting the CPU's max extended CPUID leaf to zero if CPUID(0x80000000).EAX doesn't indicate a valid CPUID extended range. While at it, add a comment, similar to kernel/head_32.S, clarifying the CPUID(0x80000000) sanity check. References: 8a50e5135af0 ("x86-32: Use symbolic constants, safer CPUID when enabling EFER.NX") Fixes: 3da99c977637 ("x86: make (early)_identify_cpu more the same between 32bit and 64 bit") Signed-off-by: Ahmed S. Darwish Signed-off-by: Ingo Molnar Cc: Andrew Cooper Cc: H. Peter Anvin Cc: John Ogness Cc: x86-cpuid@lists.linux.dev Link: https://lore.kernel.org/r/20250506050437.10264-3-darwi@linutronix.de Signed-off-by: Sasha Levin --- arch/x86/kernel/cpu/common.c | 17 +++++++++-------- 1 file changed, 9 insertions(+), 8 deletions(-) diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c index 0ff057ff11ce9..5de4a879232a6 100644 --- a/arch/x86/kernel/cpu/common.c +++ b/arch/x86/kernel/cpu/common.c @@ -1005,17 +1005,18 @@ void get_cpu_cap(struct cpuinfo_x86 *c) c->x86_capability[CPUID_D_1_EAX] = eax; } - /* AMD-defined flags: level 0x80000001 */ + /* + * Check if extended CPUID leaves are implemented: Max extended + * CPUID leaf must be in the 0x80000001-0x8000ffff range. + */ eax = cpuid_eax(0x80000000); - c->extended_cpuid_level = eax; + c->extended_cpuid_level = ((eax & 0xffff0000) == 0x80000000) ? eax : 0; - if ((eax & 0xffff0000) == 0x80000000) { - if (eax >= 0x80000001) { - cpuid(0x80000001, &eax, &ebx, &ecx, &edx); + if (c->extended_cpuid_level >= 0x80000001) { + cpuid(0x80000001, &eax, &ebx, &ecx, &edx); - c->x86_capability[CPUID_8000_0001_ECX] = ecx; - c->x86_capability[CPUID_8000_0001_EDX] = edx; - } + c->x86_capability[CPUID_8000_0001_ECX] = ecx; + c->x86_capability[CPUID_8000_0001_EDX] = edx; } if (c->extended_cpuid_level >= 0x80000007) { -- 2.39.5