From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (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 A38F2351C1E; Wed, 7 Oct 2026 02:04:36 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1791338677; cv=none; b=VaXLtPAOSLZT5985CNVAq5MvCK0sv0wXBWntJ9dgO/5emllMeaTRFWTOSPhQVmiligdajoJBsSKaW/X/j2cAjCb1iKtitJjk117y4DEHgy2viOgG6woVfw9c+Gp25GPGW6PN+7MZjcp3J2Vu1Oq2aSglU5+vV9W4hQWSqOZkuOY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1791338677; c=relaxed/simple; bh=PwzR/ysO+s24mTwsG/AacQqcFPleu87XDZpPpXmgw/Y=; h=Date:To:From:Subject:Message-Id; b=CV14mYKxRBIJiN5NSOFVfJKPh2ghVx0zpIVVShM8wtbXhDhWDQnd3cLnBy6fIikiZ219AkD0NUpIK0l/kgM2vEi3gKmYVfQUtEyoTF6f8Kb8PwNS9FqKf8uTNLahs+mcJ7sJoseYNniMhYOxKwZBMWoVgWGkxxqQP6/OhFUWu+U= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b=gma53Nmg; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b="gma53Nmg" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 76A1C1F0089C; Wed, 7 Oct 2026 02:04:36 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux-foundation.org; s=korg; t=1791338676; bh=GgdayeBC89P3JHvyvvCmvvAzWpEcs/PN7NCA/oCuOdo=; h=Date:To:From:Subject; b=gma53NmggWukp4p1Hi+xjqiX575sRb1BNwmuo/vqoNZcSB1lIcsVeJBKN4kxGtEhW hjPBEntKQBj/pBDOBI9RRsoc/h7G1aS8JWHUGJGArX3FiHZ2GYkMLECDlLIdaVdoFG /iJ9zE+OgEn5nx58sL7EsIM85ikVRE1Fdpu0ARuQ= Date: Tue, 06 Oct 2026 19:04:36 -0700 To: mm-commits@vger.kernel.org,vbabka@kernel.org,stable@vger.kernel.org,peterz@infradead.org,mingo@redhat.com,kees@kernel.org,include@grrlz.net,kmehltretter@gmail.com,akpm@linux-foundation.org From: Andrew Morton Subject: [merged mm-nonmm-stable] fork-honor-task_structs-declared-alignment.patch removed from -mm tree Message-Id: <20261007020436.76A1C1F0089C@smtp.kernel.org> Precedence: bulk X-Mailing-List: mm-commits@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: The quilt patch titled Subject: fork: honor task_struct's declared alignment has been removed from the -mm tree. Its filename was fork-honor-task_structs-declared-alignment.patch This patch was dropped because it was merged into the mm-nonmm-stable branch of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm ------------------------------------------------------ From: Karl Mehltretter Subject: fork: honor task_struct's declared alignment Date: Fri, 10 Jul 2026 14:39:57 +0200 Since commit cb7ca40a3882 ("x86/fpu: Make task_struct::thread constant size"), struct task_struct is declared __attribute__((aligned(64))) on all architectures. But fork_init() still sets the task_struct slab cache's alignment to align = max(L1_CACHE_BYTES, ARCH_MIN_TASKALIGN) which is smaller than 64 on architectures whose cache lines are below 64 bytes: e.g. 32 on ARMv5. In practice plain SLUB happens to hand out 64-byte-aligned objects anyway. With CONFIG_SLUB_DEBUG_ON the red-zone padding shifts objects to the requested alignment. With CONFIG_UBSAN_ALIGNMENT=y a boot on QEMU versatilepb (ARM926EJ-S, v7.2-rc2, gcc 13.3) floods the console with reports like: UBSAN: misaligned-access in include/linux/sched.h:2087:9 member access within misaligned address c295d7e0 for type 'struct task_struct' which requires 64 byte alignment CPU: 0 UID: 0 PID: 15 Comm: pr/ttyAMA-1 Not tainted 7.2.0-rc2 #1 VOLUNTARY Set the slab alignment to at least the type's declared alignment. Link: https://lore.kernel.org/20260710123957.31774-1-kmehltretter@gmail.com Fixes: cb7ca40a3882 ("x86/fpu: Make task_struct::thread constant size") Signed-off-by: Karl Mehltretter Signed-off-by: Andrew Morton Reviewed-by: Bradley Morgan Assisted-by: Claude:claude-fable-5 Cc: Ingo Molnar Cc: Kees Cook Cc: Peter Zijlstra Cc: Vlastimil Babka Cc: --- kernel/fork.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) --- a/kernel/fork.c~fork-honor-task_structs-declared-alignment +++ a/kernel/fork.c @@ -858,7 +858,8 @@ void __init fork_init(void) #ifndef ARCH_MIN_TASKALIGN #define ARCH_MIN_TASKALIGN 0 #endif - int align = max_t(int, L1_CACHE_BYTES, ARCH_MIN_TASKALIGN); + int align = max3(L1_CACHE_BYTES, ARCH_MIN_TASKALIGN, + __alignof__(struct task_struct)); unsigned long useroffset, usersize; /* create a slab on which task_structs can be allocated */ _ Patches currently in -mm which might be from kmehltretter@gmail.com are docs-mm-ksm-use-the-renamed-ksm-structure-names.patch mm-secretmem-fix-the-enable-parameter-description.patch mm-damon-core-preserve-the-quota-passed-to-damon_new_scheme.patch mm-damon-tests-core-kunit-test-preservation-of-quota-state.patch mm-damon-tests-core-kunit-test-psi-goal-values-with-explicit-samples.patch ocfs2-cluster-hold-a-reference-on-the-heartbeat-thread.patch resource-kunit-stop-selecting-get_free_region.patch kcov-report-spurious-pcs-in-the-interrupt-selftest.patch squashfs-fix-fragment-index-table-sizing-overflow-on-32-bit.patch squashfs-make-the-fragment-index-table-bounds-check-overflow-safe.patch