From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id E8E3FC44512 for ; Thu, 16 Jul 2026 19:38:10 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id A86CB6B00CF; Thu, 16 Jul 2026 15:38:09 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id A10586B00D0; Thu, 16 Jul 2026 15:38:09 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 8FFCC6B00D1; Thu, 16 Jul 2026 15:38:09 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0012.hostedemail.com [216.40.44.12]) by kanga.kvack.org (Postfix) with ESMTP id 666B66B00CF for ; Thu, 16 Jul 2026 15:38:09 -0400 (EDT) Received: from smtpin27.hostedemail.com (lb01a-stub [10.200.18.249]) by unirelay03.hostedemail.com (Postfix) with ESMTP id F100DA025F for ; Thu, 16 Jul 2026 19:38:08 +0000 (UTC) X-FDA: 84995650656.27.99B8921 Received: from out-174.mta0.migadu.com (out-174.mta0.migadu.com [91.218.175.174]) by imf30.hostedemail.com (Postfix) with ESMTP id BE25280002 for ; Thu, 16 Jul 2026 19:38:06 +0000 (UTC) Authentication-Results: imf30.hostedemail.com; dkim=pass header.d=linux.dev header.s=key1 header.b=LTnTyNuJ; dmarc=pass (policy=none) header.from=linux.dev; spf=pass (imf30.hostedemail.com: domain of shakeel.butt@linux.dev designates 91.218.175.174 as permitted sender) smtp.mailfrom=shakeel.butt@linux.dev ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1784230687; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=T2ZOq4dcOvepgVVTva9wQ6lBd75ccF2O3Asl/sIYvfo=; b=ILWUlQ7g26jD++Ymf1rcZG2M7FUBACTMTEZ/QiUFg2Alsimw/+DupwZtrD0/S6iwUXlmBi zlgjoyR6C0Q1jKwzqaSZsCiSrkWFzRS5twLDbXXofeSGfjgRamXzTaq8m0AIQeVLvvy28l OCHCF7c4BAOJUncCPYbQ4YCGh7QiEmo= ARC-Authentication-Results: i=1; imf30.hostedemail.com; dkim=pass header.d=linux.dev header.s=key1 header.b=LTnTyNuJ; dmarc=pass (policy=none) header.from=linux.dev; spf=pass (imf30.hostedemail.com: domain of shakeel.butt@linux.dev designates 91.218.175.174 as permitted sender) smtp.mailfrom=shakeel.butt@linux.dev ARC-Seal: i=1; a=rsa-sha256; d=hostedemail.com; s=arc-20220608; cv=none; t=1784230687; b=eKl7NqjYCUmk54VhQH38s52wIIMj5IMWLb11D+YxnqKtIYVqcOWZ3xl7auzg2xLhQHDcEX 0/2ucTpHffFxg3DAAc8dc3kD9oe1nZeSMNVJgIaXYcrP6HXBSsY6P4keElK5SS5Fyxq8Eo wwaFtfyIopzNoJIaFSY56widR9wurD8= Date: Thu, 16 Jul 2026 12:37:54 -0700 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1784230684; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=T2ZOq4dcOvepgVVTva9wQ6lBd75ccF2O3Asl/sIYvfo=; b=LTnTyNuJ23iroHykIM9DWrv5Mc+O853WCxFpELImlcaiqni67nE3vSlsN4B3i58rHJJmfg eqCChLNCNxO/mnMiL+QNF30S3vqP4JnMignVWSspJmANeC6YfH+aHds/LiPbhhc7jY2oL9 S8tFD2tjlBv5OY1k2a2QtG+zyOED6X0= X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: Shakeel Butt To: "Harry Yoo (Oracle)" Cc: Vlastimil Babka , Andrew Morton , Hao Li , Christoph Lameter , David Rientjes , Roman Gushchin , "Liam R. Howlett" , Suren Baghdasaryan , Hao Ge , Kees Cook , Pedro Falcato , Danielle Constantino , linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH slab/for-next-fixes v3 0/4] mm/slab: fix unbounded recursion in free path with memalloc profiling Message-ID: References: <20260713-kmalloc-no-objext-v3-0-47c7bd138de7@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260713-kmalloc-no-objext-v3-0-47c7bd138de7@kernel.org> X-Migadu-Flow: FLOW_OUT X-Rspamd-Queue-Id: BE25280002 X-Stat-Signature: odhdcr7h6joemsucyw3wsj4fma7gewy8 X-Rspam-User: X-Rspamd-Server: rspam12 X-HE-Tag: 1784230686-887046 X-HE-Meta: U2FsdGVkX1/zd794blwZLBLHmiptQX5pW3jEsjBc/wfkECkOmrl95QBF5rjqJueXzT8GAISF3AapYi2gt6vh5RJXeZzLnp8q90DjouSOkEAS7PyYMo2APSdhKTaNaxIeaSnCmyY9GGkWaHlZkH24VrvZDItcY9gX7SQ60gIY58DDteCqJdWBb4yYDvuBf+rNuVYnHcv1ebHjZ8uBMPN5MVIRIVO+9PFSDo+29x69SR8fIMqFx5KLey5926xrZa4ztARLkKV8QSGXapgjmgnJ+uvC5ux2ELoO5dCD6tGtH2gfIkwQ3oPkgPF6P+82+83mY9M8khnDggJ3dtiFQz5Ni3z/bh68RmWrNL/3sqVovVmTRA2P32qDOckrTwzvyG2KBv4UNpraYkXSjP/dlLGewuswsR6pZ9bczJCe31Yblfzo3ACL3GHLLHCsm5m5vNVCUjeQi6EhlLdzMd0t7FG6FsExsaXusVlJVDY91GQTwBtps6ML2V5WbGz1K47lz8zlU6DkTqJzm3I6iB1hYsgoW6x2uPhIklU5ng3IkQXoYHK3Wbfg4w0pAjw7ap4oWQ/OyhXzoQABr9FXDWmpr1OrNRVQ8pVcgfsNWfBO0+pyKsedS/qdbeY9twgWOdUwE4Vb2SwgMTiMeX7X7XU6HLwbsZGAE0sxO96+Qu8aDnuWekJ9tR3zVwa8PaY41lrObA0H4mq56xJhXMQrH6kR6SGQyIanJKAazPxnaz6yxJlXaHk/FHrSa1Xyf/fKvGCb4X4xF9qYHszZECtBWQlETQ3stJ7bvH2igBKKHSSpS+m0GvCdq4c+cbaQlvQ47iLShji+nJbebKV8Vvd2PMqK2kqeT6WAtUmMIRU8w6Ho5Gwl79Qy7Z44pLbdHs+fKlaOBXHiTMf0QXFNRbjA923T2/mGMAK68n/e7c26KlGQlGwACKR8yiCzaj/OfOwBzq2D9LeGg5gSHFIHw9NxYUB3tF5 H12jLsSC 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 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Mon, Jul 13, 2026 at 11:28:48PM +0900, Harry Yoo (Oracle) wrote: > This is a follow-up fix after the recent discussion [1]. > See patch 4 for the detailed description on the bug. > > Based on slab/for-next-fixes (af9ea231c0b45) and is available at > git.kernel.org [2]. > > Instead preventing cycles by bumping up the allocation size of obj_exts > arrays, it introduces a new kmalloc type called KMALLOC_NO_OBJ_EXT and > disallow formation of cycles between kmalloc types when allocating > obj_exts arrays. obj_exts arrays of normal kmalloc caches are served > from KMALLOC_NO_OBJ_EXT caches (that don't have obj_exts), and all other > obj_exts arrays are served from normal kmalloc caches. > > I tried to reuse SLAB_ALLOC_NO_RECURSE to make kmalloc_slab() select > KMALLOC_NO_OBJ_EXT, but it was not great because it does not allow > sheaves for those caches. So I introduced a new slab alloc flag > SLAB_ALLOC_NO_OBJ_EXT. > > To avoid huge confusion, I had to decouple "disallowing sheaves" > semantics from SLAB_NO_OBJ_EXT and introduced SLAB_NO_SHEAVES. > > While this cannot be directly backported to v6.18 and v6.12 due to lack > of SLAB_ALLOC_* flags and kmalloc_flags(), I don't this will be > particularily challenging to backport it. Instead of a new slab alloc > flag, we can use __GFP_NO_OBJ_EXT to select KMALLOC_NO_OBJ_EXT as > kmalloc caches don't have sheaves in v6.18 anyway. > > [1] https://lore.kernel.org/linux-mm/9a139365-28e6-4f1e-b35b-7f6091e9aa14@kernel.org > > [2] https://git.kernel.org/pub/scm/linux/kernel/git/harry/linux.git/log/?h=kmalloc-no-objext-v3r1 > > To: Vlastimil Babka > To: Andrew Morton > To: Hao Li > To: Christoph Lameter > To: David Rientjes > To: Roman Gushchin > To: Suren Baghdasaryan > To: Hao Ge > To: Kees Cook > To: Pedro Falcato > To: Shakeel Butt > To: Danielle Constantino > To: Liam R. Howlett > Cc: linux-mm@kvack.org > Cc: linux-kernel@vger.kernel.org > Signed-off-by: Harry Yoo (Oracle) I tested next-20260716 which has this series against next-20260707 which does not have the fix. The reproducer were able to trigger the leak/recursion on next-20260707 but not on next-20260716. So, you can add: Tested-by: Shakeel Butt