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 E9843171D2; Mon, 19 May 2025 18:19:56 +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=1747678798; cv=none; b=ulGObdJ2VPGdpUL+020tKaIOqNDV0FZhdeKMHMfOcjViTt+VxhqfQ5KLBwRK7eZ0FeJP22gQNx3zqjBWZe05MJWDRe0MLAQiynE+41PengpyifkIwCWODQNlYqNsLG0ccRw+Cd5htnezsOH2HYlcLqNh6qv+WB8rsIExk+t88rQ= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1747678798; c=relaxed/simple; bh=Kmxs929ZOWp5SNI8oGlYhKZHAd9hzey0D1QNUWF3RgE=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=dvoPn2e0mjkrhyr4kSc59lMk16cNQ1LYfDZOOWFJbjB1kPmEqcRg4xiVtaBgDDzUYlFqNkunwzPwj5g5xoT505jwl+7gUDInbOBcOF1idnVAVnhCCMs1+oMvSe0nq7NNlIwI6Q7hZVnaDsy+aeKgKzd1gOpEFuTCgPHv4UYvS84= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=JgY69Bxp; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="JgY69Bxp" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 59B97C4CEE4; Mon, 19 May 2025 18:19:56 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1747678796; bh=Kmxs929ZOWp5SNI8oGlYhKZHAd9hzey0D1QNUWF3RgE=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=JgY69Bxpk8AB1cILkkJz4CG7zJR5luHUNFhoERMmkl6OheX7U5QK1c42iQk8QQI4U fkEUGwySu+xY0JGEhEwhtzVaDImXqaiBNJ0i7fQd0I/lpQSDd6W+eUyJyusu/8aUCt LKbV/pJizCJ4cOxOK8WRFbplqE44G+8hYLZ3SK37TOQPQrnIy2DGF0dWZc74cdtQ/1 C/Fx7IMt9bxIbUwJmhzBgVad/pkY1RBDVSMbkkOI2Y6P5qpTjJTBR53gdNOeU9j1P6 /+EkQzWXO1G2VQcOMJgtdLNwj5SXyFf+5XrNay5rX5Y/kHP/eJ6SqjaqmECuy0Fbth SiribDQorXD3Q== Date: Mon, 19 May 2025 11:19:53 -0700 From: Kees Cook To: =?iso-8859-1?Q?Micka=EBl_Sala=FCn?= Cc: Randy Dunlap , Steven Rostedt , Stephen Rothwell , Linux Next Mailing List , Linux Kernel Mailing List , linux-security-module@vger.kernel.org, =?iso-8859-1?Q?G=FCnther?= Noack Subject: Re: linux-next: Tree for May 16 (security/landlock/ruleset.c) Message-ID: <202505191117.C094A90F88@keescook> References: <20250516202417.31b13d13@canb.auug.org.au> <20250519.jiveise8Rau8@digikod.net> Precedence: bulk X-Mailing-List: linux-next@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20250519.jiveise8Rau8@digikod.net> On Mon, May 19, 2025 at 05:29:30PM +0200, Mickaël Salaün wrote: > On Fri, May 16, 2025 at 07:54:14PM -0700, Randy Dunlap wrote: > > > > > > On 5/16/25 3:24 AM, Stephen Rothwell wrote: > > > Hi all, > > > > > > Changes since 20250515: > > Thanks for the report. > > It is the same warning as reported here: > https://lore.kernel.org/all/202501040747.S3LYfvYq-lkp@intel.com/ > > I don't know what the actual issue is though. > > > > > on i386: > > > > In file included from ../arch/x86/include/asm/string.h:3, > > from ../include/linux/string.h:65, > > from ../include/linux/bitmap.h:13, > > from ../include/linux/cpumask.h:12, > > from ../include/linux/smp.h:13, > > from ../include/linux/lockdep.h:14, > > from ../security/landlock/ruleset.c:16: > > ../security/landlock/ruleset.c: In function 'create_rule': > > ../arch/x86/include/asm/string_32.h:150:25: warning: '__builtin_memcpy' accessing 4294967295 bytes at offsets 20 and 0 overlaps 6442450943 bytes at offset -2147483648 [-Wrestrict] > > 150 | #define memcpy(t, f, n) __builtin_memcpy(t, f, n) > > | ^~~~~~~~~~~~~~~~~~~~~~~~~ > > ../security/landlock/ruleset.c:137:9: note: in expansion of macro 'memcpy' > > 137 | memcpy(new_rule->layers, layers, > > | ^~~~~~ > > > > > > Full randconfig file is attached. The trigger appears to be CONFIG_PROFILE_ALL_BRANCHES, and GCC getting tricked into thinking check_mul_overflow() returns true: In file included from ../arch/x86/include/asm/string.h:3, from ../include/linux/string.h:65, from ../include/linux/bitmap.h:13, from ../include/linux/cpumask.h:12, from ../include/linux/smp.h:13, from ../include/linux/lockdep.h:14, from ../security/landlock/ruleset.c:16: ../security/landlock/ruleset.c: In function 'create_rule': ../arch/x86/include/asm/string_32.h:150:25: warning: '__builtin_memcpy' accessing 4294967295 bytes at offsets 0 and 0 overlaps 6442450943 bytes at offset -2147483648 [-Wrestrict] 150 | #define memcpy(t, f, n) __builtin_memcpy(t, f, n) | ^~~~~~~~~~~~~~~~~~~~~~~~~ ../security/landlock/ruleset.c:137:9: note: in expansion of macro 'memcpy' 137 | memcpy(new_rule->layers, layers, | ^~~~~~ 'create_rule': event 1 ../include/linux/compiler.h:69:46: 68 | (cond) ? \ | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 69 | (__if_trace.miss_hit[1]++,1) : \ | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~ | | | (1) when the condition is evaluated to true 70 | (__if_trace.miss_hit[0]++,0); \ | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ../include/linux/compiler.h:57:69: note: in expansion of macro '__trace_if_value' 57 | #define __trace_if_var(cond) (__builtin_constant_p(cond) ? (cond) : __trace_if_value(cond)) | ^~~~~~~~~~~~~~~~ ../include/linux/compiler.h:55:28: note: in expansion of macro '__trace_if_var' 55 | #define if(cond, ...) if ( __trace_if_var( !!(cond , ## __VA_ARGS__) ) ) | ^~~~~~~~~~~~~~ ../include/linux/overflow.h:270:9: note: in expansion of macro 'if' 270 | if (check_mul_overflow(factor1, factor2, &bytes)) | ^~ 'create_rule': event 2 ../arch/x86/include/asm/string_32.h:150:25: 150 | #define memcpy(t, f, n) __builtin_memcpy(t, f, n) | ^~~~~~~~~~~~~~~~~~~~~~~~~ | | | (2) out of array bounds here ../security/landlock/ruleset.c:137:9: note: in expansion of macro 'memcpy' 137 | memcpy(new_rule->layers, layers, | ^~~~~~ make[1]: Leaving directory '/srv/code/gcc-bug' I'll take a look at ways to make either the overflow macros or memcpy robust against this kind of weirdness... -- Kees Cook