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 0DA41541E65 for ; Thu, 15 Oct 2026 16:47:19 +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=1792082854; cv=none; b=bQUo2WwQ7CjqFx7ShwQmxfEe5COZIlXUGXdYPdOQ4biAzcvqvqObkkf5rCqqd0KY/CjtZ2EX+Utuj8BwGdZDlRiWMsnVyv7dxrP/KIaBim2tTnTM/8EkDcQER0yXvoOByzMj/5oLp5KBaO7WeMmoqRsB7il9pvKQbsGVJ6gQuXU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1792082854; c=relaxed/simple; bh=ot46ivAS9lB/QC6ux2x2sv5hxNw6Zt/FWp52VKBlLx8=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=rdaC0T/SA8lBiwyiWZGU3k89TLc4fsv3tEGXmlNTlIp028trqmdAZtJq83HLei4KeNBVM3vOYPCEarbNkrgH/l0tkiSysKE1jh2aLX+okEfJuWA4FuHS8XqU56Gs/DxCME33xsW/Nzz2adqRXhkqdy+lmq3594+WTdoo8lPV9Zk= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=Q1Cb6XZ+; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="Q1Cb6XZ+" Received: by smtp.kernel.org (Postfix) with ESMTPSA id C3CC11F000C4; Thu, 15 Oct 2026 16:47:16 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1792082838; bh=2TgTdmbdNunwh4BUXo3hMM2/ke1MBTDNI7seN15BAQw=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=Q1Cb6XZ+yCNE2dqg4oFZEsejxSK8qmDhJ9qEH5U7kwG8exMHtomAVngfn84FHrpiH Crue1/GAN6blJk/5iWA0EyUN4+zwWK7l9ZaE2iviSXNO1pU6jVvMlDj8HFiQVsEE7s 0L5eRAmhabTPpZEYzkJ2DxTDPxpK1pp7wqHs2vK8MayT5Dg2wSuGdvH85xwnyezDzO vJLGqcJ4nNuaINUFqjMIePNLCJ7Aou43z48qi1MYqYYJv80pwmEcD21V92fBrGXW2+ AO1sE55E4Qx5izoy0MhsiIkBDxq5457H5ScKxqNzcQ+kq/TpgFNkJ2iFYrDjc09OzI SJm5eJpnOhkxQ== Message-ID: Date: Thu, 15 Oct 2026 18:47:14 +0200 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] mm/slub: initialize the free pointer of the bootstrap kmem_cache_node Content-Language: en-US To: Karl Mehltretter , Harry Yoo , Andrew Morton Cc: Hao Li , Christoph Lameter , David Rientjes , Roman Gushchin , Shengming Hu , linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <20261010203906.93156-1-kmehltretter@gmail.com> From: "Vlastimil Babka (SUSE)" Autocrypt: addr=vbabka@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit On 10/10/26 22:39, Karl Mehltretter wrote: > With slub_debug=FZPU, validating kmem_cache_node reports > > BUG kmem_cache_node (Not tainted): Freepointer corrupt > Object 0xffff888000140040 @offset=64 fp=0x5a5a5a5a5a5a5a5a > > and taints the kernel. Poisoning places the bootstrap object's free > pointer outside the object, where check_object() checks it even while > allocated. > > early_kmem_cache_node_alloc() previously took this object from a > freelist with an initialized pointer. It now takes it from the slab > iterator and builds the freelist only for the remaining objects, > leaving its pointer filled with POISON_INUSE. > > Initialize the bootstrap object's free pointer to NULL. > > Fixes: dc795d4c0282 ("mm/slub: defer freelist construction until after bulk allocation from a new slab") > Assisted-by: LLM > Signed-off-by: Karl Mehltretter Reviewed-by: Vlastimil Babka (SUSE) > --- > QEMU x86_64 and custom QEMU SH7785LCR model, slub_debug=FZPU: > validation reports "Freepointer corrupt" before the fix, clean after. > > mm/slub.c | 1 + > 1 file changed, 1 insertion(+) > > diff --git a/mm/slub.c b/mm/slub.c > index 54ec125033571..9a20aa820bb0f 100644 > --- a/mm/slub.c > +++ b/mm/slub.c > @@ -7777,6 +7777,7 @@ static void early_kmem_cache_node_alloc(int node) > > n = next_slab_obj(kmem_cache_node, &iter); > BUG_ON(!n); > + set_freepointer(kmem_cache_node, n, NULL); > > slab->inuse = 1; > build_slab_freelist(kmem_cache_node, slab, &iter);