From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-108-mta187.mxroute.com (mail-108-mta187.mxroute.com [136.175.108.187]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 98701221F1F for ; Tue, 19 May 2026 00:20:08 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=136.175.108.187 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1779150010; cv=none; b=b3fdl2zAMmlVRO7tKeu3pTkDQCKW/BdCB/btusEGJXaAu1Y1NOcb5zRm8ywtFXqa94/Ks9Q+Hu8TDGP9mMLxQg6jPofaCtvQDSai9YtjLVqCfAeJ7gmEem0KsdDHrWvDGdFPoyvbQQ2zW2Y3XRbVSHHfNoiW002sTn8PuZ3dUsk= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1779150010; c=relaxed/simple; bh=MdUU1wqw7M7+hjy9Kiscz6aK6KJgNl83gpqCLEt4HGw=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=mjC7CYfTj+31Sj5HxZCFaMwOCHre0xRD3lXA9ggvu6UAxuyrz7KKK3ytT1gSjuyW3aG0QTuLLc30jQy/qRzuQ1UkeWlawsGY3Eo5QmsRrFPKPhDDxnvzAY9EoWZhP1UaVnETf9buKeHJvVR781tY9e7ra0OVjEmctXmCs5ZZj+Y= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=wii.dev; spf=pass smtp.mailfrom=wii.dev; dkim=pass (2048-bit key) header.d=wii.dev header.i=@wii.dev header.b=aLZICZu7; arc=none smtp.client-ip=136.175.108.187 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=wii.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=wii.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=wii.dev header.i=@wii.dev header.b="aLZICZu7" Received: from filter006.mxroute.com ([136.175.111.3] filter006.mxroute.com) (Authenticated sender: mN4UYu2MZsgR) by mail-108-mta187.mxroute.com (ZoneMTA) with ESMTPSA id 19e3d95f2ce00067f7.00d for (version=TLSv1.3 cipher=TLS_AES_256_GCM_SHA384); Tue, 19 May 2026 00:14:57 +0000 X-Zone-Loop: 87554ce25c4daa70790573e03a0908d2869f6f58aeb5 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=wii.dev; s=x; h=In-Reply-To:Content-Transfer-Encoding:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To:Content-ID: Content-Description:Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc :Resent-Message-ID:List-Id:List-Help:List-Unsubscribe:List-Subscribe: List-Post:List-Owner:List-Archive; bh=fMA0+wZo70MBMLEaecLU1LClg4illspgGkTP+hxG9bw=; b=aLZICZu7bpj6wuzhlp7SxDTkN9 N0QSkc9ujoCSGiVBHwj5qEqCz3VxHlVYp1DHXkeNZna4RfgrkcCE+UqPNK/kto2IzX5YqlA7DraXs xDHE9PYL+iTkqBX7hCNKMYQKuXvyBbOhy5FbA4dVr6D3nUPLBFBOjWj+DZCUVq/kBabFXFWd+/lsc 1vS8B4F+poYohn9Cf4KCgMLM19fpmJG96W92uvvJ8/6Xgvj4fv8Nm8yPMHse1xASKHmvs/n80wkhD yzyCrfltB2Ce4tLrzBqhRcG/yotOX/k0h4CtQ8q3CTsBUwrczkjJCylBkUmQWD5YXLTD0Ioyj2htj q4R5/3Ig==; Date: Tue, 19 May 2026 00:14:34 +0000 From: Richard Patel To: "H. Peter Anvin" Cc: x86@kernel.org, Rick Edgecombe , Yu-cheng Yu , Dave Hansen , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Andy Lutomirski , Kees Cook , Peter Zijlstra , Shuah Khan , linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 4/7] x86: ban 32-bit sigreturn when user IBT enabled Message-ID: References: <20260517183024.16292-1-ripatel@wii.dev> <20260517183024.16292-5-ripatel@wii.dev> Precedence: bulk X-Mailing-List: linux-kselftest@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: X-Authenticated-Id: ripatel@wii.dev On Mon, May 18, 2026 at 01:22:19PM -0700, H. Peter Anvin wrote: > On May 17, 2026 11:30:21 AM PDT, Richard Patel wrote: > >IBT is not implemented for 32-bit and cannot be enabled using a > >32-bit syscall. However, a 64-bit thread could far jump into 32-bit. > >Therefore, 32-bit sigreturn must be banned until IBT supports that > >environment. > Dumb question: is there any reason not to just enable it for 32 bits? It doesn't seem that it would be that big of a delta to Just Do It.™ > > That being said, I suspect the number of users will be very small if any. Yes, partially, good call. It'd be tricky for legacy IA32 signals. sigframe_ia32 would need to be modified I think. For rt_sigframe_ia32 (rt_sigreturn) we can put it in ucontext_ia32::uc_flags. I'll fix it in v2 later this week and add tests.