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=1793108578; b=NjliNRCCYA5EFtj/GdHai4lCf/47TNspaaBLZkasqEVfe4n6iwuOaCT8w3LzZg4CMYeI 1+kVEIobpmVPnhAZSBhe4QhdLmY6z+QYyvEOdETPPA4VPz5J61pfqg8d3l4v90DkvMi2/ iazt4sQTf9Cb0Epf8M/JfjIu510dwGdGvbPWdMgyFVAZ67VVPiaB3/xqr1TzozgxOj8Da bxQ94KFofVqD5VUsvuRW1d1Fm6idYke/HBA6cizryWqeu2vw8Wz32GuGr7Tt/SR1pwFBg c5ssYMD8fqYiDurEW5xyxb+o0YdMI1eQqgAT7hWX3sIZqXmx0RdohaOhe+9tOxqJHig== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1793108578; 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=0+f6IJooHiQbF9wAyC4ax/+y1Gmk+/E4quNL5EJAkoQ=; b=UmsMlh+nwZ61GDhMYH5tDmC77xyLkgoNSmn73Jz9c6+D6xoSk5K8KVm5M3ffnzrXfUkH qRYa5jhX2qV7gGqOk7kXI4GPkUKzpMg3jLZ1P4eLE3KmUx4yIK3R8NY5sN7JLF52tdfmW oVULAciIcbbi8e/n4QZzHyh/yqPbh9uLIJ6tQJs9nXdsSBCxRmdBZL0nMbS0/v3Gqdqdk PzixwuRYqzOFsG23GIHRLtRsqITw5HLCMBO/eTMH93QbO7QEzgyPtXZT3/oeJ2D83TfmN i3bSX9dWEo/Ds35452efVH1tYvAnr+A4O6c/8qXoq9OacafDiM72u3RYBd4BVXH6wZA== 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="O/cT7rN4"; 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 8429E606A31B; Tue, 27 Oct 2026 13:42:58 +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=O/cT7rN4 Received: by smtp.kernel.org (Postfix) with ESMTPSA id 234691F01825; Tue, 27 Oct 2026 13:42:40 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1793108578; bh=0+f6IJooHiQbF9wAyC4ax/+y1Gmk+/E4quNL5EJAkoQ=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=O/cT7rN4J4QJA9+qKjooI/EO5er0turCIeVkTDeBg9nmgtchbI+fpxO9S6+r+oBWY LwmatZaw1QbMHP8ScOJ6R+l2fGSrhmt7f6UUvC43uiHkIJGDGGCW0OQjZcEIUQEPa2 w142oOqbY6kYvnslUnzMN4PB88SswCTWpes66yGol6fQLmBbkQaxbQK69GdBHy5hRV glBMz2eRymovbjCzKL0DCgcuiVWEYF4wIngi0eCG9PplngO81D5jwjFqaadaqIhz3C 3l+I0Do+I4H43SEQfhyQdeFO3NHr7grqnLgvsjGY/hUxovAgKOJx9ptbOi6w43lJzE qaE/Jiu8PIH2w== Message-ID: <38491041-d167-4ea1-8813-e75bd11cd10f@kernel.org> Date: Tue, 27 Oct 2026 14:42:38 +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 03/46] mm/memfd: check for real shmem inodes before accessing shmem state To: Mike Rapoport Cc: Andrew Morton , Johannes Weiner , Michal Hocko , Qi Zheng , Shakeel Butt , Lorenzo Stoakes , Kairui Song , Barry Song , Axel Rasmussen , Yuanchu Xie , Wei Xu , Baoquan He , Baolin Wang , "Liam R. Howlett" , Vlastimil Babka , Suren Baghdasaryan , Michal Hocko , Kees Cook , Peter Zijlstra , Jann Horn , Pedro Falcato , Hugh Dickins , Pasha Tatashin , Pratyush Yadav , "Matthew Wilcox (Oracle)" , Jan Kara , Zi Yan , Lance Yang , Rik van Riel , Harry Yoo , Alistair Popple , Nico Pache , Ryan Roberts , Dev Jain , Usama Arif , Kiryl Shutsemau , Matthew Brost , John Hubbard , Peter Xu , Will Deacon , "Aneesh Kumar K.V" , Nick Piggin , Oscar Salvador , Minchan Kim , Muchun Song , Xu Xin , Chengming Zhou , Chris Li , Kemeng Shi , Nhat Pham , Youngjun Park , Gregory Price , Joshua Hahn , Rakie Kim , Ying Huang , Jason Gunthorpe , linux-mm@kvack.org, linux-kernel@vger.kernel.org, kexec@lists.infradead.org, linux-fsdevel@vger.kernel.org, linux-arch@vger.kernel.org, linux-cxl@vger.kernel.org, stable@vger.kernel.org, Chris Mason References: <20261027-fixes_core-v1-0-6f74bec9a5bb@kernel.org> <20261027-fixes_core-v1-3-6f74bec9a5bb@kernel.org> 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: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 10/27/26 09:13, Mike Rapoport wrote: > On Tue, Oct 27, 2026 at 12:17:23AM +0100, David Hildenbrand (Arm) wrote: >> shmem_file() only checks a file's backing mapping. That mapping can belong >> to another file, as with a Coda file backed by a tmpfs container after >> mmap(). It does not establish that file_inode(file) is a shmem inode. >> >> Seal handling and memfd preservation use this check before accessing >> shmem inode state, so they can access an inode of the wrong type. >> >> Add file_inode_is_shmem() to check the inode's file operations in both >> paths. This identifies regular shmem inodes, including those used by >> memfds and ordinary tmpfs files, independently of wrapper file operations. >> >> Fixes: c49fcfcda8b5 ("mm/shmem: update file sealing comments and file checking") >> Fixes: b3749f174d68 ("mm: memfd_luo: allow preserving memfd") >> Cc: stable@vger.kernel.org >> Reported-by: Chris Mason >> Signed-off-by: David Hildenbrand (Arm) > > Reviewed-by: Mike Rapoport (Microsoft) > > With a small nit below > >> --- >> include/linux/shmem_fs.h | 6 ++++++ >> mm/memfd.c | 8 +++++--- >> mm/memfd_luo.c | 2 +- >> mm/shmem.c | 5 +++++ >> 4 files changed, 17 insertions(+), 4 deletions(-) >> >> diff --git a/include/linux/shmem_fs.h b/include/linux/shmem_fs.h >> index a7c7a96a7cbf9..2ceca7993e4f5 100644 >> --- a/include/linux/shmem_fs.h >> +++ b/include/linux/shmem_fs.h >> @@ -117,8 +117,14 @@ extern unsigned long shmem_get_unmapped_area(struct file *, unsigned long addr, >> unsigned long len, unsigned long pgoff, unsigned long flags); >> extern int shmem_lock(struct file *file, int lock, struct ucounts *ucounts); >> #ifdef CONFIG_SHMEM >> +bool file_inode_is_shmem(const struct inode *inode); > > Do we really need the file_ prefix in this name? Good point, I intuitively added it. Can drop. Thanks! -- Cheers, David