From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=100.103.45.18 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1793021985; b=FPQimlQp12dDaCwIvGD4HtuxcaW/3pHMDTP82TMcT0KOwbnZM6zPb8bjXWTbuK698fgk IYUl1lsX6zOk59wd+niTswzpK5mujY6uk0n3Kdz6NrOhVIMjzqSjLX46SdxJNIZM1bS7l OhmKYGGv3AiVnEyNgTM12nJ/QifZriYOuoBFrf+yr8XaTt0CyYb2dCBX3FE2sdxh1qkND WckciVqc2XI8xovuueoPEaoGMqmvubHdh0lqemU209t2jJRoo4f+1zuRI2Qq6xeZ336O1 swKfA4smzeyF+IACUkbhqxM9wLVqWex59uY9RysyxGuC/recc5msSMBZJlZK7gLMlXg== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1793021985; h=Received:DKIM-Signature:Date:From:To:Cc:Subject:Message-ID: References:MIME-Version:Content-Type:Content-Disposition:In-Reply-To; bh=+29/JeDTgI2q6Zdd2oPF6MhnTmquWtxwp3oevCRZyMI=; b=Z4JKQNR0yYKTIclB46BXsZSrEzdhkxnvJMxi/6wwwS4Id4NJJC+w9JvS7RkA3xsHqzYT mLZ5aVf5l70QTaJc0/waliH4LJM5k+4E0M5gCy0bw32py9pho5KUgj9QKfzirrwkc7LuX 8QJDeVSImsaXiuEDMAXrFajI5XjkH/xYC4U5TJxou49srKll5rBrGicO2b8yhmjH6CoeP iWNSq9ghJFKoHz20AFyiCfl6qGr1a0px6m4nTAzP4xIKOLqzKTshND51jrLIOvz433VBK HZmmqZRGycP5nCvrey61p3f3LyrXI1tVHZRweHDxfTa+hOUKQdlLlTwq5Lsun/StIhw== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=i5V4VCQr; arc=none smtp.remote-ip=100.103.45.18 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1) server-digest SHA256) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id EC1B3606A31A; Mon, 26 Oct 2026 13:39:44 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key, unprotected) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=i5V4VCQr Received: by smtp.kernel.org (Postfix) with ESMTPSA id B8DFA1F01825; Mon, 26 Oct 2026 13:39:41 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1793021984; bh=+29/JeDTgI2q6Zdd2oPF6MhnTmquWtxwp3oevCRZyMI=; h=Date:From:To:Cc:Subject:References:In-Reply-To; b=i5V4VCQrdHU+uG2pJYqRPhqkSzGsM4xSLU1XJ0z+Tn+sGBvGl6PS5AjTKVdmcv7K9 UfzYyrhEX+CTogKDpTIY8lSfX1ObveUxmAkok+oz+mpAYPvI8fHZHyt0umP7bvrRHs BeNRToBTnOZoQW8aS/ryia3YZ/4UTSkJso5hJLv3xJLZ2C51/dd1tulN+/RHimZul7 DiXbkdNPUq/Nv5Ktmq35EoqixXG6MoyeZZg4wNF0PxRH4sBVkkbdL3yOv4vcKZi4tz BpWuka+s9hoS3MQ0yrRcYrO7hYd8o7kThsrGemf08Ua37ljn+RT6XbUviQ0AeCcBh0 YvlSe4qWWm1Sw== Date: Mon, 26 Oct 2026 13:39:39 +0000 From: "Lorenzo Stoakes (ARM)" To: "David Hildenbrand (Arm)" Cc: Andrew Morton , Ngoc Quy , liam@infradead.org, Vlastimil Babka , Jann Horn , Pedro Falcato , Muhammad Usama Anjum , linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, stable@vger.kernel.org Subject: Re: [PATCH] fs/proc/task_mmu: pin mm_users in do_pagemap_scan() Message-ID: References: <20261014095540.3261469-1-ngocquy0700@gmail.com> <20261019174659.42c3529d5e35563cc6e5244c@linux-foundation.org> <9aa49812-1132-458e-9bf5-6dba8b476b26@kernel.org> X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <9aa49812-1132-458e-9bf5-6dba8b476b26@kernel.org> On Sun, Oct 25, 2026 at 11:55:59AM +0100, David Hildenbrand (Arm) wrote: > On 10/20/26 02:46, Andrew Morton wrote: > > All looks good and checks out for me, thanks. > > > > Except... > > > >> --- a/fs/proc/task_mmu.c > >> +++ b/fs/proc/task_mmu.c > >> @@ -3231,15 +3231,18 @@ static long do_pagemap_scan(struct mm_struct *mm, unsigned long uarg) > >> size_t n_ranges_out = 0; > >> int ret; > >> > >> + if (!mm || !mmget_not_zero(mm)) > >> + return -ESRCH; > > > > Why the new test for !mm? The current call chain guarantees this is a > > cant-happen and the current do_pagemap_scan will cheerfully oops if > > mm==NULL. > > I'd just keep it for consistency with all the other checks in this file? Agreed. -- Cheers, Lorenzo