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 B7DDACF8576 for ; Thu, 20 Nov 2025 09:25:10 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 228906B0096; Thu, 20 Nov 2025 04:25:10 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 2005F6B0098; Thu, 20 Nov 2025 04:25:10 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 13C5D6B0099; Thu, 20 Nov 2025 04:25:10 -0500 (EST) 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 020346B0096 for ; Thu, 20 Nov 2025 04:25:09 -0500 (EST) Received: from smtpin26.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay08.hostedemail.com (Postfix) with ESMTP id BF3A21407EF for ; Thu, 20 Nov 2025 09:25:09 +0000 (UTC) X-FDA: 84130451538.26.21A3163 Received: from tor.source.kernel.org (tor.source.kernel.org [172.105.4.254]) by imf26.hostedemail.com (Postfix) with ESMTP id 1FB6B140009 for ; Thu, 20 Nov 2025 09:25:07 +0000 (UTC) Authentication-Results: imf26.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=uwLOIVrC; spf=pass (imf26.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=1763630708; 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=rWSmvSxXpg/mSZQH6kbqxm/dkIi5PSx5PsRdWHSKC6k=; b=yxlYHsoMzXjBZR5Al1Fw3VzwDMPIyrU0UNKlFhZKHpWBQqL4JCWWU2JQ8OZ55T0mXosrq9 AXfYPS37pgJTxhKhzOJIkaCY+CpMvlCHBYjWHVZz3kOIlnIRmgD9G2xBxpspwI5aRMNKKh vV1EIWvzTjlgcv2QrZF4cbFPoS4s89M= ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1763630708; a=rsa-sha256; cv=none; b=npcvzna0X1yykq3jRA4w1BVSUGgsS/nxUwtF9EI4UmCtEsBgkiqUsaMIp7YEN6gybard40 XrMD3QbeeT2yfdxMczMeo3UnisTgN9UEzt15/dVbY0er+Xv0pXwhIVCQb4ROaRUuTIV6y1 rEGUX8FNIxsIRTRpI/Dl79WkRnR6YJM= ARC-Authentication-Results: i=1; imf26.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=uwLOIVrC; spf=pass (imf26.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 6CE1F60007; Thu, 20 Nov 2025 09:25:07 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 0C8E6C4CEF1; Thu, 20 Nov 2025 09:25:03 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1763630707; bh=Zxcj9YrpAEfvPY91o1U5hwiHCXNZdysrcM08YutqhjA=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=uwLOIVrCHyj293/4WH4HOG2zu281VSxljjgOmaymHYjlguERPfAvjpub/HQXMaBV3 MndUSzl+xdJ8n6JaBOtzKpWB1DbPDCNe/+bZKBLtAV6C8SJAgHO9iQQ6phudPOCvEt yzp5BKvBVMliCmTQjTZBAfV0UB4leb7yzJ5V5vhTjJRDnseA2Bh0fx6+sV8qEy6VgS tB29W2mj6vEzz8sO8gakgTCpvxTjCXTuQim5ckt/P4nF/5rXOVHSiqdq9zEukpNm3Q 2cFd6XYCoDx8kmoueTfcrs8w8yvqO0o9js8bETMGbuvRdVUN6AK8MX4foCpnH0OJkr mQGfW84PZULcQ== Message-ID: <875584d7-5a68-4f7a-8549-2a9cd6c7f9d8@kernel.org> Date: Thu, 20 Nov 2025 10:25:01 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [RFC PATCH 1/3] mm/huge_memory: prevent NULL pointer dereference in try_folio_split_to_order() To: Zi Yan , Lorenzo Stoakes Cc: Andrew Morton , Baolin Wang , "Liam R. Howlett" , Nico Pache , Ryan Roberts , Dev Jain , Barry Song , Lance Yang , Miaohe Lin , Naoya Horiguchi , linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <20251120035953.1115736-1-ziy@nvidia.com> <20251120035953.1115736-2-ziy@nvidia.com> From: "David Hildenbrand (Red Hat)" Content-Language: en-US In-Reply-To: <20251120035953.1115736-2-ziy@nvidia.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam12 X-Rspam-User: X-Rspamd-Queue-Id: 1FB6B140009 X-Stat-Signature: 6fhx5u8sa1bige8m41czqsgp5jwunnar X-HE-Tag: 1763630707-404243 X-HE-Meta: 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 sfJImjDk QrLOEvzkkUzM1jCl+Zhcacxr6p52RgLLttLx/mFCDBcEdh9auwK2fPPdqiWYOKWchYKCW9IwpYY03vdmgkDeYjfJC5LjhmbUt7m8IiRj/0IrmiU0JXORCcbymguKD8AN6ANAHrhpjYVniXYZCowexKDZWbORNUgXJVFodyPFflHBZIo2Sp6A7I9wG7vGpKOsSj5tE9c4xqIJnNhsO1f0p/gSv15u/Ze+PioIRX9niuN/gzeFVFQUNFBkcwawvq6brGFXzn2vOyhMiLd/bmyhcnSxU4FaRspLvVDQDvkWhxI7g72/3UFgJFympWcre12dkrf8vB9/F4RF54Pqt3uw8RmYee5u1kp8g4YztyRAEIVa3AIIgcSPvbvxl8/hWkO0jRh8aC91L1XQ69tftHSFmEmTOh3ncGDeCtiIZ X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 11/20/25 04:59, Zi Yan wrote: > folio_split_supported() used in try_folio_split_to_order() requires > folio->mapping to be non NULL, but current try_folio_split_to_order() does > not check it. Add the check to prevent NULL pointer dereference. > > There is no issue in the current code, since try_folio_split_to_order() is > only used in truncate_inode_partial_folio(), where folio->mapping is not > NULL. > > Signed-off-by: Zi Yan > --- > include/linux/huge_mm.h | 7 +++++++ > 1 file changed, 7 insertions(+) > > diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h > index 1d439de1ca2c..0d55354e3a34 100644 > --- a/include/linux/huge_mm.h > +++ b/include/linux/huge_mm.h > @@ -407,6 +407,13 @@ static inline int split_huge_page_to_order(struct page *page, unsigned int new_o > static inline int try_folio_split_to_order(struct folio *folio, > struct page *page, unsigned int new_order) > { > + /* > + * Folios that just got truncated cannot get split. Signal to the > + * caller that there was a race. > + */ > + if (!folio_test_anon(folio) && !folio->mapping) > + return -EBUSY; > + > if (!folio_split_supported(folio, new_order, SPLIT_TYPE_NON_UNIFORM, /* warns= */ false)) > return split_huge_page_to_order(&folio->page, new_order); > return folio_split(folio, new_order, page, NULL); I guess we'll take the one from Wei https://lkml.kernel.org/r/20251119235302.24773-1-richard.weiyang@gmail.com right? -- Cheers David