From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=209.85.217.52 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1793206437; b=AssdZhmfEUEyiVCDFmu+sA2wtFhbAJSDAshf4N2KDTOusomNHbBfg3F1taUyBj4c4h+G FdrdweJpUg+Fo5pipJWMYKQaQusQxj4NQZFtjyjKDDDwDzYZ1mhdQQYhTYvwaH2kEt/03 jmtrDC4ciFLIXARP+drBVz1g31OmBcb73V5A7d/XR/4UB1jcOQjBoHOaQfAXkj+mSbueY GdZFJMQ8JwueDFKpBuA+zUvDE9BAdQUWcBhEcs81zLWcupBeGjsU2LmuTgWstyvc2CX4z OLJYS0FOMpZif5O/VwvgNBfgBCj5SGtwFzNkazFVXwTgYYdufNPLMW8LB5/NJ3pBoZw== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1793206437; h=DMARC-Filter:Received:DKIM-Signature:X-Google-DKIM-Signature: X-Forwarded-Encrypted:X-Gm-Message-State:X-Gm-Gg:X-Received:Received: Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; bh=jQ5eyf1zl1dztY8G8GNDjIbe5i6XtlGMZ8AEehh0sP8=; b=Hp4cfy0LAMNmV2SUxd8dYaWYxLvhnTQeHe43qboK8OV4R0AtUvvDESKcClfvUZPH5LhJ oY2ijUE2EiZGTLDuROl//T+2dhnsG2GnDuZAbIXnvZBw8RVpChlLQSbeJQRCsg161oImq X4SCOz4MXXg3CqA5tG5YK1bgJhY8HbRTHxu+2h2ebwbFgTWKPgk5CHER2SDirjX7CQBVK hIDB5tAjNxEzoFVfdgm1mSUtjTNlSt3lh1jZYo2iZldteYu//LHUe4d61S39lvqARVCTf 3YCBxggN1OAxxdztJ4xNVTSwLB2I600yN08EygclnMB2fgZwCJGybh8wY3Oke+zJxiw== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass header.from=soleen.com; spf=pass smtp.mailfrom=soleen.com; dkim=pass header.d=soleen.com header.i=@soleen.com header.a=rsa-sha256 header.s=google header.b=XDq4mZkF; arc=none smtp.remote-ip=209.85.217.52 Received: from mail-vs1-f52.google.com (mail-vs1-f52.google.com [209.85.217.52]) (using TLSv1.3 with cipher TLS_AES_128_GCM_SHA256 (128/128 bits) key-exchange X25519 server-signature ECDSA (prime256v1) server-digest SHA256) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 53375606A31A for ; Wed, 28 Oct 2026 16:53:57 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.2 smtp.subspace.kernel.org 53375606A31A Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=soleen.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=soleen.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key, unprotected) header.d=soleen.com header.i=@soleen.com header.a=rsa-sha256 header.s=google header.b=XDq4mZkF Received: by mail-vs1-f52.google.com with SMTP id ada2fe7eead31-7cb6dc850c7so398657137.0 for ; Wed, 28 Oct 2026 09:53:57 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=soleen.com; s=google; t=1793206436; x=1793811236; darn=vger.kernel.org; h=in-reply-to:content-disposition:content-type:mime-version :references:message-id:subject:cc:to:from:date:from:to:cc:subject :date:message-id:reply-to:content-type; bh=jQ5eyf1zl1dztY8G8GNDjIbe5i6XtlGMZ8AEehh0sP8=; b=XDq4mZkFFwWiuClm+CVqUYc4wMUeEj61wwTEJ2ZEwdKAAZOVs4mAkia9/oOPQEGvZ7 0CPllEZOpo+2Vx7NH/qeJyuqrXNeGxLOX9kPYs9EQ9wuoJxqmE3014fXKocl5hQCZSSq jYT4HKvnmSRh02d1ht2QsIKl81mDMWNV+vmtqq/q3kRlDKFLvoFwvUwOFm0i3nE1GCkQ 0TjmSaJ0QDxHwSaQMTz0/I03VsYupX2JpKIJaxwXOjS22DLQQPY2UaMVlL2DtL/m4NnR nHVimsjgnDDTHtl7ghN+41KfpsxRYFoCjEcPBdzS03ioSJ55NDDAbq0L5U9RWlFtVa5Q rq3Q== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20260707; t=1793206436; x=1793811236; h=in-reply-to:content-disposition:content-type:mime-version :references:message-id:subject:cc:to:from:date:x-gm-gg :x-gm-message-state:from:to:cc:subject:date:message-id:reply-to :content-type; bh=jQ5eyf1zl1dztY8G8GNDjIbe5i6XtlGMZ8AEehh0sP8=; b=pTnb/z7ZTaxuF6hVE4tJOkLbvE7CurrzIceKXpDhLxmZhhqNtGM0ut7F4c/MUyOwKL raNXgAtmkRziUabx16+y5R6ykK2QiNasnL15WlK6f/kGkl2nvypa1xJZPYLyernzetme 3ZaBgVThj+yXhB4JzpSeUpAm//fbYtMZBjTlaffYaUCoVYb9kHBbIX8On+ZT4+RiyBYA m7RjDarcpFgV+51P8cuTYRcF0REElMM/ef1qWz2KI4C74v7/x//KC2Xj6pINoQbUdhev eL7CRWoIR88kIuVnhvTLkz+dwDoxXfpNewPltMYi+3CtNg/xAbS5I0jiRaGmXPjfuXuR 2gqw== X-Forwarded-Encrypted: i=1; AKwUvBxmeBLl3qkaT88XstCPzAFbPLH60etN2FnkRendy6sQ3eGM7MwLj2Tt7hjLI9nxklSXuF3ahlNEj7z6aEhZ@vger.kernel.org X-Gm-Message-State: AFq9FYKqhYltAdcMOhOKQE21baYZaZlbK7hs43LdhEC+efmEWuWWzjcs 25IFdCIyooBZaBT/DOAMWbA3hrhGqcRVp0hcpKEooIy9qI56L2nJ8ayrsSolV4vBqfo= X-Gm-Gg: AYBFou3rxQJS19NiIEc0O5poO2kvvAfJpkQdrZ5b4Sa9/pTVfr89C1IkA42se4r/sbt sEl4755JfunTFqYgRaJ9M9d6qDm6GoyD9lp1Zqlodgz1QLvMePLtqmGD/CR7DcptEm9I4FeKRVn aye1UtdJbwowfHx2l563tlGiKdZIK23QERhzAPkocOKmSt/pvJZ3blzNPYNbayIWtvk5fQ5OgOe MYZNb4NG5WZPj7k0Kge3UDgwXg5+Gv+6+Gmf7H/ufebzv+hQK7P6Rex8I5bc59PgAnjGuXlfS8h 5Y+z9foxZlw+TvrbR7TolpExFuUlf5hOwoPQBTx3tQqyTeLRqZbFbcep5P47czm9kR6nm3dKvPM 2nYO0Z6ZC9K7dW45crNg31oFAoLxIdmukyNLWVaJmQ5JkBsYF7gXhByugqWJt9nkhTq2075jZWl sCPjXw+LMsXksqjvdFpJk1MoGf4liyEvx8xGELpm6cZM5c/kCmMV6cvcEWZQAEOoSgDP2DDbPgs EpQqff2SNOtHi+v8qj85NjMiHn/bDdgNxqPPrZ8jD40cjq5A4r/IHsfyNJVw46GahCTR7R+kbZO v2MP3BRs3SF3xzMqxBGTZmaGa2/Un8i9d3noopF8oHI/QZnRuIy49umEWTTSW76CDabvIRojGDc Rc9kZIXCOqlZ5KXq1jf1o2HD1a3sTvQ== X-Received: by 2002:a05:6102:3e8d:b0:7cb:bb33:8412 with SMTP id ada2fe7eead31-7d03a5063b4mr1453208137.10.1793206435862; Wed, 28 Oct 2026 09:53:55 -0700 (PDT) Received: from google.com (16.49.199.35.bc.googleusercontent.com. [35.199.49.16]) by smtp.gmail.com with ESMTPSA id a1e0cc1a2514c-991259db2d3sm6495987241.6.2026.10.28.09.53.48 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 28 Oct 2026 09:53:54 -0700 (PDT) Date: Wed, 28 Oct 2026 12:53:47 -0400 From: Pasha Tatashin 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 , 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 , 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-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=us-ascii Content-Disposition: inline In-Reply-To: <20261027-fixes_core-v1-3-6f74bec9a5bb@kernel.org> On 10-27 00:17, 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) > --- > 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); > bool shmem_mapping(const struct address_space *mapping); > #else > +static inline bool file_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 0f6fff004f5e4..7d2da23157003 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 (file_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 59de210bee5f9..c0811407ce397 100644 > --- a/mm/memfd_luo.c > +++ b/mm/memfd_luo.c > @@ -582,7 +582,7 @@ 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 file_inode_is_shmem(inode) && !inode->i_nlink; > } Yeah, file_ is not needed, otherwise: Reviewed-by: Pasha Tatashin > > static unsigned long memfd_luo_get_id(struct file *file) > diff --git a/mm/shmem.c b/mm/shmem.c > index fadf23f9e21ed..0d41aac125df9 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 file_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 >