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=1793306054; b=gsXT6BHyZKGlwXbqiaWShy5Sv4mI/ImA/rEKYH8sy2Pc5+1YBs2/+Qk0k7nbN0AilJjt PL9tbR5ryJkpgZiESib42DyZQIiU51tF9nQSuKBo0S5JNoMXP+/GwVjCP1MoD+jg+CLYT hP739jBLiw1VinbRfAPqCGih79a1oz5PeFQrPK3HRnVeih2mMJ4/TDAOzHm4ycz+R9di9 GNyGiEhMQhsErT+6hHx4axHUy4DK/C3iunn688+PvI49dEV6dUft/58A9aMgG9C6drbRv 5lsG8PFIzSrlLK+Blzp6oOi8hi/P8sEYUtR/7kiXd2qegNPoWUzzWqiJfi6uN3YGCvQ== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1793306054; h=Received:DKIM-Signature:From:Date:Subject:MIME-Version:Content-Type: Content-Transfer-Encoding:Message-Id:References:In-Reply-To:To:Cc: X-Mailer:X-Developer-Signature:X-Developer-Key; bh=IUH+yaBKom46Q63QM7iBm+f59t3sGZ4mQyL9p/SX3S4=; b=V5SeLI6SjYh55ovDZ/37FEa8Q6gPrSVh3svpWKcVQMw+hIcp7Y5KU7EANKHlXow04+xZ bvu1ZAbj7yKsHcdczgUJvYVCr/T5y64qrypnDcJ5hbkhc3XrP+sJSaSItu/2GpA0Rnrdm lgNN7fLgljezueff+lhEK6wFEbp8TjEVjHWR//C+TnKCLrg7k9LgjC+HDO0fVsrm1iZLx vATyZUcdgvfGJfuEyScQ4S+teuC/6/pcmeL/TX7c7Zz9tZ5crxTaE3Mj2xo+VKpMeVk1j G0A/F5Ght4oPV79jUJ+PZVB2Z24QIbQNyIM7cVbz2shYHm2urOEWpqMDzypVZ/C0a+w== 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=AQKsyj+q; 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 28512606A31D; Thu, 29 Oct 2026 20:34:13 +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=AQKsyj+q Received: by smtp.kernel.org (Postfix) with ESMTPSA id A26F31F01828; Thu, 29 Oct 2026 20:33:59 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1793306053; bh=IUH+yaBKom46Q63QM7iBm+f59t3sGZ4mQyL9p/SX3S4=; h=From:Date:Subject:References:In-Reply-To:To:Cc; b=AQKsyj+qR4bxZGp8hAtyoQ1xOy4UZyL47FxstML+FqQX7G/y7pZ8l9SOf+5ou7WnS AZ/MIxoJhVWJNFDauvFzu5zXAw5inOOKbVVHKcdXEUzqJPeX7wQfcuJQKHYfLV7cgT DBS0xvxyeqIDcCB94oXE/FoCz/yzahtQW9be2ViknnFuUwiLNKNChtzZica7dWmXmI rxJu6FqHy+hS0KRyeLYDs7SF6JTjHzt3/Fnx/dmoxM+iCSbUu0aeKsMfsauzJgHrdB M2PNJNfSKISDgyTRDXYcWYfP+czRJ+zkR1pNBo2whDOaHlVJSA2riVVk0BtrRZThlu TWT19hXESofoQ== From: "David Hildenbrand (Arm)" Date: Thu, 29 Oct 2026 21:32:58 +0100 Subject: [PATCH v2 03/47] mm/memfd: check for real shmem inodes before accessing shmem state X-Mailing-List: linux-fsdevel@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="utf-8" Content-Transfer-Encoding: 7bit Message-Id: <20261029-fixes_core-v2-3-a64ce7f83abb@kernel.org> References: <20261029-fixes_core-v2-0-a64ce7f83abb@kernel.org> In-Reply-To: <20261029-fixes_core-v2-0-a64ce7f83abb@kernel.org> To: 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 , Mike Rapoport , 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 Cc: 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 , "David Hildenbrand (Arm)" X-Mailer: b4 0.16.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=3516; i=david@kernel.org; h=from:subject:message-id; bh=llGJ6NdJiWik0yJaZwx3srvBERv6b9fGHgw5NUViur8=; b=owGbwMvMwCF2/OVpCdfQ3ZWMp9WSGLIer21Ju85syDihqpSx8kZevq/BZ7vdCS+E9j8/nxLpZ /XE2Ia3o5SFQYyDQVZMkSUo+L7By5fraqvd+Jhh5rAygQxh4OIUgImo6DP8j8p2PfZIeerUF4kK Hjnn3G2C5wiVWez72jNt+fOvrBv2ejH84b6byOPtzq2/yLfz8kkfNWWZyr3pRUYsIhJrNjtK6AX xAQA= X-Developer-Key: i=david@kernel.org; a=openpgp; fpr=1BD9CAAD735C4C3A460DFCCA4DDE10F700FF835A 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 Reviewed-by: Rik van Riel Reviewed-by: Mike Rapoport (Microsoft) Signed-off-by: David Hildenbrand (Arm) --- 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 a7c7a96a7cbf..4996420cfe60 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 inode_is_shmem(const struct inode *inode); bool shmem_mapping(const struct address_space *mapping); #else +static inline bool inode_is_shmem(const struct inode *inode) +{ + return false; +} + static inline bool shmem_mapping(const struct address_space *mapping) { return false; diff --git a/mm/memfd.c b/mm/memfd.c index 0f6fff004f5e..507c00ce0fda 100644 --- a/mm/memfd.c +++ b/mm/memfd.c @@ -211,12 +211,14 @@ static int memfd_wait_for_pins(struct address_space *mapping) static unsigned int *memfd_file_seals_ptr(struct file *file) { - if (shmem_file(file)) - return &SHMEM_I(file_inode(file))->seals; + struct inode *inode = file_inode(file); + + if (inode_is_shmem(inode)) + return &SHMEM_I(inode)->seals; #ifdef CONFIG_HUGETLBFS if (is_file_hugepages(file)) - return &HUGETLBFS_I(file_inode(file))->seals; + return &HUGETLBFS_I(inode)->seals; #endif return NULL; diff --git a/mm/memfd_luo.c b/mm/memfd_luo.c index 6b68220275eb..adaab98c8b63 100644 --- a/mm/memfd_luo.c +++ b/mm/memfd_luo.c @@ -581,7 +581,7 @@ static bool memfd_luo_can_preserve(struct liveupdate_file_handler *handler, { struct inode *inode = file_inode(file); - return shmem_file(file) && !inode->i_nlink; + return inode_is_shmem(inode) && !inode->i_nlink; } static unsigned long memfd_luo_get_id(struct file *file) diff --git a/mm/shmem.c b/mm/shmem.c index af21a89abb0f..0ca5b7f7a517 100644 --- a/mm/shmem.c +++ b/mm/shmem.c @@ -275,6 +275,11 @@ static const struct vm_operations_struct shmem_vm_ops; static const struct vm_operations_struct shmem_anon_vm_ops; static struct file_system_type shmem_fs_type; +bool inode_is_shmem(const struct inode *inode) +{ + return inode->i_fop == &shmem_file_operations; +} + bool shmem_mapping(const struct address_space *mapping) { return mapping->a_ops == &shmem_aops; -- 2.43.0