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 3F46BC43458 for ; Fri, 26 Jun 2026 16:02:15 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id EFFD76B00E8; Fri, 26 Jun 2026 12:02:13 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id ED84B6B00EA; Fri, 26 Jun 2026 12:02:13 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id DED7F6B00EB; Fri, 26 Jun 2026 12:02:13 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0012.hostedemail.com [216.40.44.12]) by kanga.kvack.org (Postfix) with ESMTP id B71666B00E8 for ; Fri, 26 Jun 2026 12:02:13 -0400 (EDT) Received: from smtpin02.hostedemail.com (lb01a-stub [10.200.18.249]) by unirelay03.hostedemail.com (Postfix) with ESMTP id 4086AA04FB for ; Fri, 26 Jun 2026 16:02:13 +0000 (UTC) X-FDA: 84922530546.02.65896F2 Received: from sea.source.kernel.org (sea.source.kernel.org [172.234.252.31]) by imf06.hostedemail.com (Postfix) with ESMTP id 55E79180018 for ; Fri, 26 Jun 2026 16:02:11 +0000 (UTC) Authentication-Results: imf06.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=OmLzHpUK; spf=pass (imf06.hostedemail.com: domain of david@kernel.org designates 172.234.252.31 as permitted sender) smtp.mailfrom=david@kernel.org; dmarc=pass (policy=quarantine) header.from=kernel.org ARC-Seal: i=1; a=rsa-sha256; d=hostedemail.com; s=arc-20220608; cv=none; t=1782489731; b=fG9U5HDM6YChx0ENwXfkaMn0Vkx4Ngi4nJEnT3/KVRTzdXde8Xq2SRngKrcA8AGYc0yELg hc6EPxH5yxa3ugp3hquV/hw1b/XjX0SjaM/6uSr+UT/DbvVuF4/+Xy/V8XDcTmB8CJvCN9 +r8GGFbaUNtzDEPJ5dqXztNOTYDXz+A= ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1782489731; 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=yGny4MDbdiGnqMNUM4Qhs7X7axB+H5dnSFgwt0189jg=; b=50mruM2wkpF9gTbAYefpk7hNsB4iG37CuQ3yF6QT4TXr31U2bSZfkzPEJPGBU7PF3JLCJj tQ8Q7z65lAX1K7+8tsqJilKfwVYmBUEz6ZGeu+kDMaXNVBLs2cb2iuhOEc7vyAO/iaV+E6 n2+Pcn+6+6ds+iAMMf5fAeTm6uErVKU= ARC-Authentication-Results: i=1; imf06.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=OmLzHpUK; spf=pass (imf06.hostedemail.com: domain of david@kernel.org designates 172.234.252.31 as permitted sender) smtp.mailfrom=david@kernel.org; dmarc=pass (policy=quarantine) header.from=kernel.org Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by sea.source.kernel.org (Postfix) with ESMTP id 6E417403E4; Fri, 26 Jun 2026 16:02:10 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 7865C1F000E9; Fri, 26 Jun 2026 16:02:06 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1782489730; bh=yGny4MDbdiGnqMNUM4Qhs7X7axB+H5dnSFgwt0189jg=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=OmLzHpUKKK3hBU/M2uh5XdhP2bUOYO7XA6cfj9DJ+nyrKKE7QgpD1xMIm49TZDDTj zKIu7MS5AW7YL4I4LQr8CxLfRYo3qjWtRNym8W6DXEslLs2/pzXGeuTKx65tBJXx0J 2QCVxfBcKpSBdeYlFkJ05GXZXZ+k6BZ6AW89vVtdSHp3AJW+5TfARK6PwEAM0MCGtR zq01mbPJxCIG2hz0MEX/2qaNgnxnKt8s2QeDPfWIeexH1rVfD12Vpr4IdD/8kvNDNa a5J1nX6aFKkkFQk8LaU8eaxehQY+25DNM9RhgqaaxlpSyLgUMqFhksF7HvCjH1z9gA TRteUxD8T1TBw== Message-ID: <08b8c447-c991-4c20-8274-3e65787d20de@kernel.org> Date: Fri, 26 Jun 2026 18:02:04 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] mm: do file ownership checks with the proper mount idmap To: Pedro Falcato , Alexander Viro , Christian Brauner , "Matthew Wilcox (Oracle)" , Andrew Morton , "Liam R. Howlett" Cc: Jan Kara , Vlastimil Babka , Jann Horn , linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org References: <20260625153853.913949-1-pfalcato@suse.de> 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: <20260625153853.913949-1-pfalcato@suse.de> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Stat-Signature: ztnupetr1b8dnt7embsybmgfz8spxpnm X-Rspam-User: X-Rspamd-Queue-Id: 55E79180018 X-Rspamd-Server: rspam02 X-HE-Tag: 1782489731-355097 X-HE-Meta: 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 e8Trvd74 VwaMMpHVctjTBap7+DtNtkngw98TVioueqt/XZJ/D7O/Sr7eIl8GQcfLPPNb8mjle0kVgr4UXQTUS1OTfUNr7ivHtrSe/Amx3QqXK8GnR4hKgLaTU/KYoRsOPdjhooVtK6FgzMjBz1DLS2JZ82eqb/3EuWdfOexxmGc9ncOoWjz9j5xxofiW1ChAWl+S15M4F9u52vvkfk+99D5Stg4T9RY3SNLf248OZ63QR9OKtxX60woDzDA3/LO1fn6hnas9IJu8HnZ9Aka+F9uaaIowybVTHRw1Ib1pVPssg Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 6/25/26 17:38, Pedro Falcato wrote: > Ever since idmapped mounts were introduced, inode ownership checks > (for side-channel protection) in mincore() and madvise(MADV_PAGEOUT) were > done against the nop_mnt_idmap, which completely ignores the file's mount's > idmap. This results in odd edgecases like: > > 1) mount/bind-mount with an idmap userA:userB:1 > 2) userB runs an owner_or_capable() check on file that is owned by userA > on-disk/in-memory, but owned by userB after idmap translation > 3) owner_or_capable() mysteriously fails as the correct idmap wasn't supplied > > In the case of mincore/madvise MADV_PAGEOUT, this is usually benign, because > file_permission(file, MAY_WRITE) will probably succeed, as it uses the proper > idmap internally, but it does not need to be the case on e.g a 0444 file > where even the owner itself doesn't have permissions to write to it. > > Since this is clearly not trivial to get right, introduce a > file_owner_or_capable() that can carry the correct semantics, and switch > the various users in mm to it. > > The issue was found by manual code inspection & an off-list discussion with > Jan Kara. > > Fixes: 9caccd41541a ("fs: introduce MOUNT_ATTR_IDMAP") > Cc: stable@vger.kernel.org > Signed-off-by: Pedro Falcato MM side LGTM Acked-by: David Hildenbrand (Arm) -- Cheers, David