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 26CB5F3ED7E for ; Mon, 13 Apr 2026 11:40:08 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 7E52C6B008A; Mon, 13 Apr 2026 07:40:07 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 795906B0092; Mon, 13 Apr 2026 07:40:07 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 6847A6B0093; Mon, 13 Apr 2026 07:40:07 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0010.hostedemail.com [216.40.44.10]) by kanga.kvack.org (Postfix) with ESMTP id 55BAE6B008A for ; Mon, 13 Apr 2026 07:40:07 -0400 (EDT) Received: from smtpin07.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay05.hostedemail.com (Postfix) with ESMTP id 052AB527FF for ; Mon, 13 Apr 2026 11:40:06 +0000 (UTC) X-FDA: 84653338854.07.C9981F5 Received: from tor.source.kernel.org (tor.source.kernel.org [172.105.4.254]) by imf07.hostedemail.com (Postfix) with ESMTP id 4861440004 for ; Mon, 13 Apr 2026 11:40:05 +0000 (UTC) Authentication-Results: imf07.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=r2SIrkyG; spf=pass (imf07.hostedemail.com: domain of david@kernel.org designates 172.105.4.254 as permitted sender) smtp.mailfrom=david@kernel.org; dmarc=pass (policy=quarantine) header.from=kernel.org ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1776080405; 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:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=5N9uqpBqtopjMp5eC3BYXp+oaBpb2p4J+TEpwP+N3uA=; b=1tlPXpR9XLw/XsJ1U5hNHtxsii6gNqd3gvRv0YQQP8rG50wM2HIHJjCH7oBXwwnWA7QgXF ouRdVA0SdfCbihG2Eawhynnqw/tNxOf0hqwDUwv+Bu/ZqQTQoAaBwYG0zRF7aBoS8EYbSx 0nribx4rky3jhC1FgnIkCMQPxOMGWPQ= ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1776080405; a=rsa-sha256; cv=none; b=qnlTiFrGhd4gmQv9/8D86QY/+Za8O3kHJdOWM1ZKl1gtviLv6+87XnPu/R87U4C5pd9f3i jipu7VxNo1gS8Nppr7VgmeKMITOI1wB+1r8qDO18eFAwwGhDMJfVBkttmP+or+cwqgi7BG 4kU6xnUduWnhAklABfgUy8lgGDrxHhw= ARC-Authentication-Results: i=1; imf07.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=r2SIrkyG; spf=pass (imf07.hostedemail.com: domain of david@kernel.org designates 172.105.4.254 as permitted sender) smtp.mailfrom=david@kernel.org; dmarc=pass (policy=quarantine) header.from=kernel.org Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by tor.source.kernel.org (Postfix) with ESMTP id C824760172; Mon, 13 Apr 2026 11:40:04 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 5E87AC116C6; Mon, 13 Apr 2026 11:40:01 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1776080404; bh=xgHY69iAejNrSVk/EKAw9xtankmfSUeCz0/D+lTjBKA=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=r2SIrkyG+YIVZ+NYdaru7uPldmoVi9ikfWzsR8oWWPT0XvXEUkpO3VBzAkVOD3spF vdR8l2MejZuSx/RHaKOr9MYUWUouWd+60ud41qrpTPkZHHdwUKfZejLhDiQGTU5hBr mgVEZzieH7RYhEcPGTRFp1+SiFDuqHht0kqdCD8/0ySbgXLF70F6wgNR5zLoJJ6LPs tLiL3XdAXGFxbfToZFjFSpKoCjFUgZcMXCAXkYIv9HCeCbjl2EEhmErpeUy656ertR oFkftLThQ/fVlw8FreN4z8PP13gg4+X4+sG040WwwmA50uGqABuognfxUczAuJqZM/ kaVj1yhFuxm9Q== Message-ID: <8eda3f8b-b811-4303-aefb-4b23aeeff16c@kernel.org> Date: Mon, 13 Apr 2026 13:39:58 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2] mm: thp: Fix refcount leak in thpsize_create() error path To: Guangshuo Li , Andrew Morton , Lorenzo Stoakes , Zi Yan , Baolin Wang , "Liam R. Howlett" , Nico Pache , Ryan Roberts , Dev Jain , Barry Song , Lance Yang , linux-mm@kvack.org, linux-kernel@vger.kernel.org Cc: stable@vger.kernel.org References: <20260412175428.2613383-1-lgs201920130244@gmail.com> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; keydata= xsFNBFXLn5EBEAC+zYvAFJxCBY9Tr1xZgcESmxVNI/0ffzE/ZQOiHJl6mGkmA1R7/uUpiCjJ dBrn+lhhOYjjNefFQou6478faXE6o2AhmebqT4KiQoUQFV4R7y1KMEKoSyy8hQaK1umALTdL QZLQMzNE74ap+GDK0wnacPQFpcG1AE9RMq3aeErY5tujekBS32jfC/7AnH7I0v1v1TbbK3Gp XNeiN4QroO+5qaSr0ID2sz5jtBLRb15RMre27E1ImpaIv2Jw8NJgW0k/D1RyKCwaTsgRdwuK Kx/Y91XuSBdz0uOyU/S8kM1+ag0wvsGlpBVxRR/xw/E8M7TEwuCZQArqqTCmkG6HGcXFT0V9 PXFNNgV5jXMQRwU0O/ztJIQqsE5LsUomE//bLwzj9IVsaQpKDqW6TAPjcdBDPLHvriq7kGjt WhVhdl0qEYB8lkBEU7V2Yb+SYhmhpDrti9Fq1EsmhiHSkxJcGREoMK/63r9WLZYI3+4W2rAc UucZa4OT27U5ZISjNg3Ev0rxU5UH2/pT4wJCfxwocmqaRr6UYmrtZmND89X0KigoFD/XSeVv jwBRNjPAubK9/k5NoRrYqztM9W6sJqrH8+UWZ1Idd/DdmogJh0gNC0+N42Za9yBRURfIdKSb B3JfpUqcWwE7vUaYrHG1nw54pLUoPG6sAA7Mehl3nd4pZUALHwARAQABzS5EYXZpZCBIaWxk ZW5icmFuZCAoQ3VycmVudCkgPGRhdmlkQGtlcm5lbC5vcmc+wsGQBBMBCAA6AhsDBQkmWAik AgsJBBUKCQgCFgICHgUCF4AWIQQb2cqtc1xMOkYN/MpN3hD3AP+DWgUCaYJt/AIZAQAKCRBN 3hD3AP+DWriiD/9BLGEKG+N8L2AXhikJg6YmXom9ytRwPqDgpHpVg2xdhopoWdMRXjzOrIKD g4LSnFaKneQD0hZhoArEeamG5tyo32xoRsPwkbpIzL0OKSZ8G6mVbFGpjmyDLQCAxteXCLXz ZI0VbsuJKelYnKcXWOIndOrNRvE5eoOfTt2XfBnAapxMYY2IsV+qaUXlO63GgfIOg8RBaj7x 3NxkI3rV0SHhI4GU9K6jCvGghxeS1QX6L/XI9mfAYaIwGy5B68kF26piAVYv/QZDEVIpo3t7 /fjSpxKT8plJH6rhhR0epy8dWRHk3qT5tk2P85twasdloWtkMZ7FsCJRKWscm1BLpsDn6EQ4 jeMHECiY9kGKKi8dQpv3FRyo2QApZ49NNDbwcR0ZndK0XFo15iH708H5Qja/8TuXCwnPWAcJ DQoNIDFyaxe26Rx3ZwUkRALa3iPcVjE0//TrQ4KnFf+lMBSrS33xDDBfevW9+Dk6IISmDH1R HFq2jpkN+FX/PE8eVhV68B2DsAPZ5rUwyCKUXPTJ/irrCCmAAb5Jpv11S7hUSpqtM/6oVESC 3z/7CzrVtRODzLtNgV4r5EI+wAv/3PgJLlMwgJM90Fb3CB2IgbxhjvmB1WNdvXACVydx55V7 LPPKodSTF29rlnQAf9HLgCphuuSrrPn5VQDaYZl4N/7zc2wcWM7BTQRVy5+RARAA59fefSDR 9nMGCb9LbMX+TFAoIQo/wgP5XPyzLYakO+94GrgfZjfhdaxPXMsl2+o8jhp/hlIzG56taNdt VZtPp3ih1AgbR8rHgXw1xwOpuAd5lE1qNd54ndHuADO9a9A0vPimIes78Hi1/yy+ZEEvRkHk /kDa6F3AtTc1m4rbbOk2fiKzzsE9YXweFjQvl9p+AMw6qd/iC4lUk9g0+FQXNdRs+o4o6Qvy iOQJfGQ4UcBuOy1IrkJrd8qq5jet1fcM2j4QvsW8CLDWZS1L7kZ5gT5EycMKxUWb8LuRjxzZ 3QY1aQH2kkzn6acigU3HLtgFyV1gBNV44ehjgvJpRY2cC8VhanTx0dZ9mj1YKIky5N+C0f21 zvntBqcxV0+3p8MrxRRcgEtDZNav+xAoT3G0W4SahAaUTWXpsZoOecwtxi74CyneQNPTDjNg azHmvpdBVEfj7k3p4dmJp5i0U66Onmf6mMFpArvBRSMOKU9DlAzMi4IvhiNWjKVaIE2Se9BY FdKVAJaZq85P2y20ZBd08ILnKcj7XKZkLU5FkoA0udEBvQ0f9QLNyyy3DZMCQWcwRuj1m73D sq8DEFBdZ5eEkj1dCyx+t/ga6x2rHyc8Sl86oK1tvAkwBNsfKou3v+jP/l14a7DGBvrmlYjO 59o3t6inu6H7pt7OL6u6BQj7DoMAEQEAAcLBfAQYAQgAJgIbDBYhBBvZyq1zXEw6Rg38yk3e EPcA/4NaBQJonNqrBQkmWAihAAoJEE3eEPcA/4NaKtMQALAJ8PzprBEXbXcEXwDKQu+P/vts IfUb1UNMfMV76BicGa5NCZnJNQASDP/+bFg6O3gx5NbhHHPeaWz/VxlOmYHokHodOvtL0WCC 8A5PEP8tOk6029Z+J+xUcMrJClNVFpzVvOpb1lCbhjwAV465Hy+NUSbbUiRxdzNQtLtgZzOV Zw7jxUCs4UUZLQTCuBpFgb15bBxYZ/BL9MbzxPxvfUQIPbnzQMcqtpUs21CMK2PdfCh5c4gS sDci6D5/ZIBw94UQWmGpM/O1ilGXde2ZzzGYl64glmccD8e87OnEgKnH3FbnJnT4iJchtSvx yJNi1+t0+qDti4m88+/9IuPqCKb6Stl+s2dnLtJNrjXBGJtsQG/sRpqsJz5x1/2nPJSRMsx9 5YfqbdrJSOFXDzZ8/r82HgQEtUvlSXNaXCa95ez0UkOG7+bDm2b3s0XahBQeLVCH0mw3RAQg r7xDAYKIrAwfHHmMTnBQDPJwVqxJjVNr7yBic4yfzVWGCGNE4DnOW0vcIeoyhy9vnIa3w1uZ 3iyY2Nsd7JxfKu1PRhCGwXzRw5TlfEsoRI7V9A8isUCoqE2Dzh3FvYHVeX4Us+bRL/oqareJ CIFqgYMyvHj7Q06kTKmauOe4Nf0l0qEkIuIzfoLJ3qr5UyXc2hLtWyT9Ir+lYlX9efqh7mOY qIws/H2t In-Reply-To: <20260412175428.2613383-1-lgs201920130244@gmail.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: 4861440004 X-Stat-Signature: wepfxnr65r5c4uafgciw9xoq38egww7c X-Rspam-User: X-Rspamd-Server: rspam07 X-HE-Tag: 1776080405-40981 X-HE-Meta: U2FsdGVkX1+n2nexKlsLlwuaXfYVcQtfJDJ0awHvAmHwZ9gyfwQaE8snt782cwPE5DVLsqMpNSkzIGPN6zHHBaOWOpwivYWPCBXUmbNT2Oj6mODkRoptUNC6zzhyUOMFH7b4/wiesZunBADepniHUSIL2bkQhYGqx95hcyJBh/CHtOvBknb9ALKN5/XQ5o5AO1ycWmeWvpQgVt3IOaEUEf2jZ9GGt92mJ5G+Rq8xYyJYGpwOXQoaYjkg97al3VYWjncxmKAzpRnNKXV6aEu2a6J3vvDAgO4/O5vkcy0sTvDLkYIbn1gk3kURckTw/AeQDRcC2iL/8A4xIpvzfsDXRtw5tdp7zl+Zp70755KR0HULSKg3rgNtpdZhtU/Mof1FC1RGX2HncTi+V2OQJZh2asU3Qsb7VUyUxdPb3X65b2tlWLyR4O/ev6Llj9pnzODuhYDEIN8fc4RF5Y+4bFm1B36E4FciuYJFIbDOlS2BA9kG68LySk7x00koDr5S7E1ogLuLIC+qtd1ftdHzz0tohrHsyqMxPAgcnKb7TiCqUMDanOrbr2f1HKe4WC0fslvhHdLDONOpzNIMpj5AJm9jYIVKCHhlMWsPLlaPIq3V4RqJClqG12HersJIKPCHFNc+qEWNAibiX9RqKrQxAxskdC70rYjpzRESkmUALH0ihw0shxUYgPnU3uMQ2BaegGKwBwdSRXjkq99jU4LlhGHsGvv8v8Mdl7BtsLAdwqVKriue7I/Z5wGIyixesbQI75obeVyxoBzFbZZGbrz4jEkG1Q1bO9nKO/vKuN0R97F1jqGERHH6VC9MA9COYwPzP3f0LT0KUmfjocR/axxFuxZxXkyhRSL6N+QiAug4TCUVzCE8/mvyLMqZCNJvtHeEhLmE1FJN1G9ZakLlaj5OoBrZyiKiI/yWQlWPQ0C/rVNaPUgYE9CwwWhyjut1v0TBzGMBsgMxiayvsrfVvKe+e+S Cu9YBC9O dUTG0kdRPnSbdyjr1wofK63uPbonIh+WZ1WkbduH7l6rv+xUYpkYUYwlk8kXILDjQJ2YtMXb0IhbgxWTpT6v6bLmT9zFKc0azig4A3rxuTLcH/euOmfIhHtKB0Vy0EkdO3JYPplu8HEUA4E538dpbBGatUEkNd6UYxVO9SdrHG69ugBhm8mZiOXMRLrSXS1SW735c/nA7AD1RZ3xwfQXPXAkSG8CK3uL+r0EVKfSybjJhz3QKFZ2RlaBUntpzWn6TLxUZTTrc7Dy/mgdAfUAVL3zyT55jM578vB29o7zZQXd2LOJjfXxe9eOitMzf2k43Q0Q9+0nR7NXa91HGNOmJWoIPw28rtqh3s6RL Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 4/12/26 19:54, Guangshuo Li wrote: > After kobject_init_and_add(), the lifetime of the embedded struct > kobject is expected to be managed through the kobject core reference > counting. > > In thpsize_create(), if kobject_init_and_add() fails, thpsize is freed > directly with kfree() rather than releasing the kobject reference with > kobject_put(). This may leave the reference count of the embedded struct > kobject unbalanced, resulting in a refcount leak. > > Fix this by using kobject_put(&thpsize->kobj) in the failure path and > letting thpsize_release() handle the final cleanup. Fortunately, that's only called during init, and the stars would have to align for this to ever trigger. I don't think this would ever trigger on any reasonable system, really. And if it triggers, other stuff would already be severely messed up. > > Fixes: 3485b88390b0 ("mm: thp: introduce multi-size THP sysfs interface") > Cc: stable@vger.kernel.org Which also makes me wonder whether we even care about stable here. > Signed-off-by: Guangshuo Li > --- > v2: > - Drop the incorrect UAF mention from the commit message > - Clarify that the bug is an unbalanced kobject reference in the > - kobject_init_and_add() failure path > > mm/huge_memory.c | 4 +--- > 1 file changed, 1 insertion(+), 3 deletions(-) > > diff --git a/mm/huge_memory.c b/mm/huge_memory.c > index 40cf59301c21..c8ffa188a198 100644 > --- a/mm/huge_memory.c > +++ b/mm/huge_memory.c > @@ -726,10 +726,8 @@ static struct thpsize *thpsize_create(int order, struct kobject *parent) > > ret = kobject_init_and_add(&thpsize->kobj, &thpsize_ktype, parent, > "hugepages-%lukB", size); > - if (ret) { > - kfree(thpsize); > + if (ret) > goto err; > - } kobject_init_and_add() indeed documents "If this function returns an error, kobject_put() must be called". As Andrew says, that's not what the "goto err" does. -- Cheers, David