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=1794605869; b=Vmm/ymFZCW/38nNjNpj/EnVE2wZMIXHkX6CMMP2sjwoH2bO1eJlkBD57FFoQrkrt5+/C uJ7MdQ6G5/CZK66IgtY1CZ8a5aHN1++ZQUFIm3GGVPK665IpaB8dIo6hfl1zjnc0MrmDH Z4z6f1UyeaKJLTHDG4VFRUbvnaWjcbNMpYtF3/COgls0hmAaqn/ti4cFBUgIhd2YjYhKm ULoVXIWJ6MT4K4wesaNhpsrtqoaIAcTV3x24KqsJFaWPVspcfQTCIE9mEoGK5e+EnCkvN EVxKcnYcZx+OT0pSfPzl8hLu8dYdQbjfq7vIQ3M4+xYZKnPOrb67+XjMpAYoHraQWqw== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1794605869; h=Received:DKIM-Signature:Message-ID:Date:MIME-Version:User-Agent: Subject:To:Cc:References:From:Content-Language:Autocrypt:In-Reply-To: Content-Type:Content-Transfer-Encoding; bh=PLiqukr56C60XaYU/sHWlWdxScdz3EOuf+dLUbwdnhA=; b=yQ5qkAzud2EUZ9sMF/uS9xmPR9qY6fi88EcxYRoXGGzVIKfqR8asx40MCuvDPu+uVOpn aNXPTFXlguOwQHuvIs8n6iEu/m0FciVOHmbmKqL07OYITjX3er6xBkf7IYIO+JMKhB0dq V+UuP7GxoyZhLyYHSfg5yDX7nWwO6oGIMhTaOeK57Dd7lyaKH3Y3pBk35B6Nx1ESrVE+L hexhUc8Kx8Lov82YtdbcESNxFrAxoNFc1oFONYjNUhPHlMu79c7LtH9idHBE5nEeFjEPX jrkMas+BBsLmcd/k+aY/awpU5TKsMjoJpv33WB3gPu7azjtI8Qbee5vkt2Dh0a/vULg== 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=l8iDfR4F; 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)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id B2BF0606A32D; Fri, 13 Nov 2026 21:37:49 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=l8iDfR4F Received: by smtp.kernel.org (Postfix) with ESMTPSA id A744E1F000C8; Fri, 13 Nov 2026 21:37:40 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1794605869; bh=PLiqukr56C60XaYU/sHWlWdxScdz3EOuf+dLUbwdnhA=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=l8iDfR4Fn+bZOr3+4kgWweW+qnLrj4VKaTg7QNEbpGu/bEFZFs5nxDoj/kJFmkOuy EswQFyeO0xhnKCfhg9Fxv8R+Ji1avzOxEhknOfUoFWfFiXvnBRtnwyyyT1s1E5sLGu rIPhwMSSDY/K7NBkMePLqfgNHfXEju4yXrJZUlkEDDfvGmMgZ+2xSUi5eCDJEAeMnq WMzbhlrefYk1jGACsD+PV+Ez4GFWp47Mw/5VoaKhHD++z7JVYv/6kJRB9nIiu2zwJO GmY07jFS33ITqgEDCXs0F5jYryk6WirTuUlUhlluTjjhZp/zdu9BtuPbQv8qObwJJe 2RxDNmut2VdaQ== Message-ID: Date: Fri, 13 Nov 2026 22:37:14 +0100 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 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 5/5] mm: check permissions and bounds for vm_ops->access To: "Kuehling, Felix" , Lorenzo Stoakes , "Liam R. Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Andrew Morton , Willy Tarreau , Jani Nikula , Joonas Lahtinen , Rodrigo Vivi , Tvrtko Ursulin , David Airlie , Simona Vetter , Chris Wilson , Matthew Auld , Madhavan Srinivasan , Michael Ellerman , Nicholas Piggin , "Christophe Leroy (CS GROUP)" , "Ritesh Harjani (IBM)" , Shrikanth Hegde , Rik van Riel , Benjamin Herrenschmidt Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, intel-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org, linuxppc-dev@lists.ozlabs.org, stable@vger.kernel.org, =?UTF-8?Q?Christian_K=C3=B6nig?= , Chris Mason References: <20261112-access_shite-v1-0-988a5c470db2@kernel.org> <20261112-access_shite-v1-5-988a5c470db2@kernel.org> <4b9042de-973a-4036-a6a0-2294c65a1ee1@amd.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: <4b9042de-973a-4036-a6a0-2294c65a1ee1@amd.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit On 11/13/26 21:25, Kuehling, Felix wrote: > > On 2026-11-12 17:09, David Hildenbrand (Arm) wrote: >> GUP rejects VM_IO and VM_PFNMAP mappings early. __access_remote_vm() then >> falls back to vm_ops->access without checking VMA permissions and without >> limiting the request to the VMA size. >> >> Consequently, /proc//mem can bypass protections even without >> FOLL_FORCE, or cross into another mapping without checking its >> permissions. >> >> Check VMA permissions before calling ->access and limit each request to >> the current VMA. Implement similar access permission checks as GUP, >> however: >>   (1) Reject writes to CoW mappings because the callbacks access backing >>       memory directly and cannot handle CoW. >>   (2) Allow forced writes to non-CoW mappings with VM_MAYWRITE. >> >> This intentionally breaks forced writes through legacy amdgpu PROT_NONE, >> MAP_PRIVATE debugger mappings. The workaround in commit fa5239f2af98 >> ("drm/amdgpu: workaround failed COW checks for Thunk VMAs") cleared >> VM_MAYWRITE to avoid CoW, but debugger writes still succeeded by >> exploiting the missing access-permission checks fixed here. Reads remain >> supported. Userspace must use MAP_SHARED instead; ROCm 5.5.0, released >> in May 2023, already does so. > > Thank you for considering this use case and checking the ROCm history. The patch is > > Acked-by: Felix Kuehling Thanks a lot for the confirmation, appreciated! -- Cheers, David