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 910BDCA5FA5 for ; Tue, 29 Sep 2026 08:40:22 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id B00606B0088; Tue, 29 Sep 2026 04:40:21 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id AB1286B0092; Tue, 29 Sep 2026 04:40:21 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 99F6E6B0096; Tue, 29 Sep 2026 04:40:21 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0011.hostedemail.com [216.40.44.11]) by kanga.kvack.org (Postfix) with ESMTP id 72D826B0088 for ; Tue, 29 Sep 2026 04:40:21 -0400 (EDT) Received: from smtpin10.hostedemail.com (lb01a-stub [10.200.18.249]) by unirelay04.hostedemail.com (Postfix) with ESMTP id 0F5631A0445 for ; Tue, 29 Sep 2026 08:40:21 +0000 (UTC) X-FDA: 85266153042.10.9FFB2AE Received: from tor.source.kernel.org (tor.source.kernel.org [172.105.4.254]) by imf01.hostedemail.com (Postfix) with ESMTP id 367024000B for ; Tue, 29 Sep 2026 08:40:19 +0000 (UTC) Authentication-Results: imf01.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=J8RCx2A6; dmarc=pass (policy=quarantine) header.from=kernel.org; spf=pass (imf01.hostedemail.com: domain of david@kernel.org designates 172.105.4.254 as permitted sender) smtp.mailfrom=david@kernel.org ARC-Seal: i=1; a=rsa-sha256; d=hostedemail.com; s=arc-20220608; cv=none; t=1790671219; b=BNvZzwYYSfeu8Az021Gru8KX07MIFYw74I8XrG1Ldu0oCPKUSMkhPlGfLJvqsZUjHe3cag o6swXhbRAc2xXa4k6uzCvacyhlF64ZvNvXNP6KATVdPdxtWpvP1BnPDjFe1TKQZZGsmUor yKEdxi8yJwFyMpfm8rz/4B9QhFRTNDY= ARC-Authentication-Results: i=1; imf01.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=J8RCx2A6; dmarc=pass (policy=quarantine) header.from=kernel.org; spf=pass (imf01.hostedemail.com: domain of david@kernel.org designates 172.105.4.254 as permitted sender) smtp.mailfrom=david@kernel.org ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1790671219; 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=NRmGo/s3yk59uOXehGVPyIu3WF3s3uiccw2ABWNFy+Y=; b=vbjP/oDq/ERef2iIRySpFMRcTCJ4ZCDNokh/plMMmSO6yNNyoPS4eGCDag5DXiFDsrtkT9 OjJ4S0GmZ3odtiEkMl76RaSVYUdcFqRxaMXThRiGztdHRpSviaYQHf30ZUqt8O70vAKvIv q/+U2mV1wbzW99S+Ad6V+DbTAQQJHHw= Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by tor.source.kernel.org (Postfix) with ESMTP id B714160210; Tue, 29 Sep 2026 08:40:18 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 27A841F000FF; Tue, 29 Sep 2026 08:40:15 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1790671218; bh=NRmGo/s3yk59uOXehGVPyIu3WF3s3uiccw2ABWNFy+Y=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=J8RCx2A62TDnaTbtiOzwUGzOs/DtFljh4PB4C9JQMt9SQup+lbXC+eZs7X2HWUBnt H8e0kNbLpjrZRKnY8dR1k3GZit7rPtW01boZqWO4PBI4tWYL1ScQzzrBFwDmZyKec3 XPqRat24jksIghm4MurKmraBFbcVxOkrpo/Ql2yin0sHvXmZrOSayPvZisZ70YVZZw DJihOGOJfhQS6LkyITjQU/YIUwy+RWGxskKfhA7IcgrOhwWLGfwSMKj4uNyMOs7iFU qRekMgmB3L3BPaXavkjvXbp72MmRlsoE/U54Kx4lrCWsUT3fU+1WzXrI8y0zmo5wgd THQnu6YKhBWHA== Message-ID: <3a95d0e5-7969-4b0d-988a-ead62b06b6f5@kernel.org> Date: Tue, 29 Sep 2026 10:40:13 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] mm/mlock: fix zero-length request normalization and integer overflows To: Park Tae-sun , Andrew Morton , "Liam R. Howlett" , Lorenzo Stoakes Cc: Vlastimil Babka , Jann Horn , Pedro Falcato , Michal Hocko , Mike Rapoport , Suren Baghdasaryan , linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <179066531783.50175.13377521828379196177@dgu.ac.kr> 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: <179066531783.50175.13377521828379196177@dgu.ac.kr> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam06 X-Stat-Signature: sfxtrtqpmxepnwenbp7ucatiizngthkx X-Rspam-User: X-Rspamd-Queue-Id: 367024000B X-HE-Tag: 1790671219-855291 X-HE-Meta: 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 d6a9Kt1C oPO1pYariybQK8wppr3Bl+r7mf5nM8xr5PEyUZYoemm+blRbYfF/9Fu3CNBEStB5QRshI7BKFCVKkeRhTKDPYsznA9e+oMPevsy69YXJ1rGmfqjGa3Kf72nxRjr2wUgQoqV/ZGkZZMSQJLMUVcQlji0YWXv966XDe7DT1fFoGcJL85p9xelWtn7jVWetf0NgHkIE/SZTkG3VVDdSEzTiJSijv10urs2Fcta6jgGkpQCHUsFFWsDbHNQb4K5mezXi/CNKt Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 9/29/26 07:56, Park Tae-sun wrote: > mlock() and munlock() currently normalize the requested address range > using: > > len = PAGE_ALIGN(len + offset_in_page(start)); > start &= PAGE_MASK; > > This performs multiple arithmetic operations on user-provided values > without validating intermediate overflows. > > First, a zero-length request with an unaligned address is incorrectly > converted into a non-zero page range. Because > PAGE_ALIGN(offset_in_page(start)) rounds any non-zero offset up to a > full page, a request such as mlock(0x1005, 0) falsely locks an entire > 4KB page (or fails with ENOMEM if unmapped), and munlock(0x1005, 0) > silently unlocks memory that should remain locked. Conversely, an > aligned mlock(0x1000, 0) is a no-op. Zero-length behavior should be a > consistent no-op regardless of address alignment. > > Second, a sufficiently large length wraps around to zero during page > alignment (e.g., len = ULONG_MAX). Because PAGE_ALIGN(x) is defined as: > > (((x) + PAGE_SIZE - 1) & PAGE_MASK) > > when len is close to ULONG_MAX, adding (PAGE_SIZE - 1) wraps around: > on a 64-bit system with 4KB pages, ULONG_MAX + 4095 wraps to 4094, and > masking with PAGE_MASK clears the lower 12 bits, producing 0. > When len becomes 0, the subsequent check in apply_vma_lock_flags(): > > end = start + len; > if (end == start) > return 0; > > evaluates to true and immediately returns 0 (success) without locking or > unlocking the requested memory range. Similar wrap-around issues have > previously been addressed in mincore() and madvise() by checking for > zero length after PAGE_ALIGN(). > > Finally, address addition overflow (start + len < start) is currently > detected only inside apply_vma_lock_flags(), after mmap_write_lock has > already been acquired and memlock rlimits checked, improperly returning > -ENOMEM instead of -EINVAL. Per POSIX.1-2024 and man 2 mlock, arithmetic > overflow of the requested range represents an invalid argument and must > fail with -EINVAL before modifying VMAs or acquiring locks. Note that > apply_vma_lock_flags() already contains: > > if (end < start) > return -EINVAL; > > but this was obscured because rlimit accounting preceded it. > > Introduce a common check_mlock_range() helper to: > 1. Return 0 immediately for zero-length requests without taking mmap_lock. > 2. Validate intermediate and final arithmetic additions using > check_add_overflow(). > 3. Reject lengths that wrap to zero under PAGE_ALIGN() with -EINVAL. > 4. Detect start + len address overflow before taking mmap_write_lock. > > Signed-off-by: Park Tae-sun > --- > mm/mlock.c | 55 ++++++++++++++++++++++++++++++++++++++++++++++-------- > 1 file changed, 47 insertions(+), 8 deletions(-) You call it "fix" but then I see no Fixes: tag. Which of the problems described above have reproducers (IOW can be triggered) and what is the user-visible problem? -- Cheers, David