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=1793088853; b=qQXsek1vXMCL1znebl8H8a32zFYDS9KXH7sZtQWaReT6vnZ/sjHSPyAdyOPj+TS8pG/k z0qMS+xLxR+o4ls1kdo9XT3JYTGR0hf5oMPp4tjRqXSQDNsXMYSmqcgj84OesgrbrU3tp e+Ry3QnIFu6p3WKuaRoqIxNtEuRBjC+ssy5wJ99E6KIBkgm9qFKM5QZGUNa5wX3Y8p7MF 0cvur2SHaX1t2vTBQlyTUVKc6cgEOLvwzqTD+Nrli7C8ZsDht+WRVy2iE+KdCQFe0+9iM 9qguLhXEjPzw+AvoGTtT0xyQma4SXaQEQ4nf9NlKjJEBf0pQFNZCqukrvNpeO393WYQ== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1793088853; h=Received:DKIM-Signature:Date:From:To:Cc:Subject:Message-ID: References:MIME-Version:Content-Type:Content-Disposition:In-Reply-To; bh=X817yPMZ1OWa0GxllLA7n65tTL4HKJjURd5YVC5upNo=; b=sqGTbU629OqpfCTTqHSK8r3aKYmrb65rl65AE4jUZEeeZ0dONj+wRvh5Ng0zdUGW5nmL gmvpQomjpq1s0np3iJyRUltec04cYTLrhh/VnDv2pWfTSgHsfH53jBzzq9vOs0wlLhfPO SgMxv64iF0q7vbdLMpKsM4byGdrl/7Kleqi1HsC9uegPciCyGcclTk53c3ODeCWTFr+2T MbR6qgBFXiQx78VpCZkjdWl0w2shKvQoNdH1KHMuTZFXFbmdEGCdH5cVHc/T1nJNj52bA OOI3hIrgM+RvOa5TZDB1pEpBGbQnTb65ep7kQMjsjhsXp2uqlI7sTZwDydLAcvywmPw== 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="J/USOVMi"; 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 0A150606A31B; Tue, 27 Oct 2026 08:14:12 +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=J/USOVMi Received: by smtp.kernel.org (Postfix) with ESMTPSA id 252CE1F01825; Tue, 27 Oct 2026 08:13:52 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1793088852; bh=X817yPMZ1OWa0GxllLA7n65tTL4HKJjURd5YVC5upNo=; h=Date:From:To:Cc:Subject:References:In-Reply-To; b=J/USOVMiZdHACMBPrC+zND6awTBbtGUCKpChcm6jDubxlHzRsgGJJ33u8eAyXrHmm Dhgy64k1zoGSzetJ6uUKZtYgTjriJplQrDD5QgepgCioCGZAn0H/62PsYvRrAHq7MD l6KQxPT3ek/jTP3ay9yQuCHmqyJ6vEXgWsvrHA/OVEIl8w0qY2qNXPJSzKqR527RVT FfER0j6vK3yc1dfQ0wPeN924r3/nVS5+UFCB/hPBBJU9NfLcCTsCBk+HMbQu7cKkEk Dk6dNn7PD/Yz5EgpKrvi4Sup3qa7fOHH3IAb+PJBxHnNh8DjdBkIMjNxtAjcJHzrHd rlwjmVWf2kcCQ== Date: Tue, 27 Oct 2026 10:13:48 +0200 From: Mike Rapoport To: "David Hildenbrand (Arm)" 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 Subject: Re: [PATCH 03/46] mm/memfd: check for real shmem inodes before accessing shmem state Message-ID: References: <20261027-fixes_core-v1-0-6f74bec9a5bb@kernel.org> <20261027-fixes_core-v1-3-6f74bec9a5bb@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: <20261027-fixes_core-v1-3-6f74bec9a5bb@kernel.org> 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? > bool shmem_mapping(const struct address_space *mapping); -- Sincerely yours, Mike.