From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 8C45815853B for ; Fri, 20 Feb 2026 00:55:04 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1771548904; cv=none; b=S76fkTWaUXYjPXAzsHrJIZBG1FQ37pu4B/UxI+KdPxs7/da/YPFLYtrj3srwK3JpwUdfffYNpwTbFb8B9DjIgY+JBo7dbXVV4gm6wZaa4PxDbNIpWse5oVVOS/jPQNekSDufKiuW0Y5z6YS4ywqH9/kqHwK1OPhSAJQFN+MEeIc= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1771548904; c=relaxed/simple; bh=619bMyWeXyUIyxv9Y+uLHhmlGKRuKXNRNhbGX51QrcY=; h=Date:To:From:Subject:Message-Id; b=DG9UT6rgCNoq5PwFfb7qGrIQBMZHIm4C3pDPmDb3MUHFNxkH08x6Mk5lVghLCV3Gzs8xxpwrD74hmetDs4xFV/WW2K6MJNP+w0NQizNrrHkr1R3M31UvwhhtJ7KfOMIw/sgehprvTzfi5MfDvhHJWfondxEU2AHEVaDY2D8aqog= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b=b2sHB7Ks; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b="b2sHB7Ks" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 0990DC4CEF7; Fri, 20 Feb 2026 00:55:04 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1771548904; bh=619bMyWeXyUIyxv9Y+uLHhmlGKRuKXNRNhbGX51QrcY=; h=Date:To:From:Subject:From; b=b2sHB7KsyTS87XC6QXDVzjYei/F88pfKsPoCTgOOzkfnqd6o5jf1F7i+qZVt3yYlp 2/rgm+T6TR/GkCeCWB6c3LzkuKNozWh6SEsAAZR2Wjv5pK/ERStmEujuWotTKFYXPh 7byboavMVMABHraRuZJKsvb5licps9pt9yniiSx4= Date: Thu, 19 Feb 2026 16:55:03 -0800 To: mm-commits@vger.kernel.org,skhawaja@google.com,rppt@kernel.org,pasha.tatashin@soleen.com,jgg@nvidia.com,hughd@google.com,graf@amazon.com,baolin.wang@linux.alibaba.com,pratyush@kernel.org,akpm@linux-foundation.org From: Andrew Morton Subject: + mm-memfd_luo-preserve-file-seals.patch added to mm-new branch Message-Id: <20260220005504.0990DC4CEF7@smtp.kernel.org> Precedence: bulk X-Mailing-List: mm-commits@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: The patch titled Subject: mm: memfd_luo: preserve file seals has been added to the -mm mm-new branch. Its filename is mm-memfd_luo-preserve-file-seals.patch This patch will shortly appear at https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-memfd_luo-preserve-file-seals.patch This patch will later appear in the mm-new branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm Note, mm-new is a provisional staging ground for work-in-progress patches, and acceptance into mm-new is a notification for others take notice and to finish up reviews. Please do not hesitate to respond to review feedback and post updated versions to replace or incrementally fixup patches in mm-new. The mm-new branch of mm.git is not included in linux-next Before you just go and hit "reply", please: a) Consider who else should be cc'ed b) Prefer to cc a suitable mailing list as well c) Ideally: find the original patch on the mailing list and do a reply-to-all to that, adding suitable additional cc's *** Remember to use Documentation/process/submit-checklist.rst when testing your code *** The -mm tree is included into linux-next via various branches at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm and is updated there most days ------------------------------------------------------ From: "Pratyush Yadav (Google)" Subject: mm: memfd_luo: preserve file seals Date: Mon, 16 Feb 2026 19:59:33 +0100 File seals are used on memfd for making shared memory communication with untrusted peers safer and simpler. Seals provide a guarantee that certain operations won't be allowed on the file such as writes or truncations. Maintaining these guarantees across a live update will help keeping such use cases secure. These guarantees will also be needed for IOMMUFD preservation with LUO. Normally when IOMMUFD maps a memfd, it pins all its pages to make sure any truncation operations on the memfd don't lead to IOMMUFD using freed memory. This doesn't work with LUO since the preserved memfd might have completely different pages after a live update, and mapping them back to the IOMMUFD will cause all sorts of problems. Using and preserving the seals allows IOMMUFD preservation logic to trust the memfd. Since the uABI defines seals as an int, preserve them by introducing a new u32 field. There are currently only 6 possible seals, so the extra bits are unused and provide room for future expansion. Since the seals are uABI, it is safe to use them directly in the ABI. While at it, also add a u32 flags field. It makes sure the struct is nicely aligned, and can be used later to support things like MFD_CLOEXEC. Since the serialization structure is changed, bump the version number to "memfd-v2". It is important to note that the memfd-v2 version only supports seals that existed when this version was defined. This set is defined by MEMFD_LUO_ALL_SEALS. Any new seal might bring a completely different semantic with it and the parser for memfd-v2 cannot be expected to deal with that. If there are any future seals added, they will need another version bump. Link: https://lkml.kernel.org/r/20260216185946.1215770-3-pratyush@kernel.org Signed-off-by: Pratyush Yadav (Google) Tested-by: Samiullah Khawaja Cc: Alexander Graf Cc: Baolin Wang Cc: Hugh Dickins Cc: Jason Gunthorpe Cc: Mike Rapoport (Microsoft) Cc: Pasha Tatashin Signed-off-by: Andrew Morton --- include/linux/kho/abi/memfd.h | 18 +++++++++++++++- mm/memfd_luo.c | 35 ++++++++++++++++++++++++++++++-- 2 files changed, 50 insertions(+), 3 deletions(-) --- a/include/linux/kho/abi/memfd.h~mm-memfd_luo-preserve-file-seals +++ a/include/linux/kho/abi/memfd.h @@ -56,10 +56,24 @@ struct memfd_luo_folio_ser { u64 index; } __packed; +/* + * The set of seals this version supports preserving. If support for any new + * seals is needed, add it here and bump version. + */ +#define MEMFD_LUO_ALL_SEALS (F_SEAL_SEAL | \ + F_SEAL_SHRINK | \ + F_SEAL_GROW | \ + F_SEAL_WRITE | \ + F_SEAL_FUTURE_WRITE | \ + F_SEAL_EXEC) + /** * struct memfd_luo_ser - Main serialization structure for a memfd. * @pos: The file's current position (f_pos). * @size: The total size of the file in bytes (i_size). + * @seals: The seals present on the memfd. The seals are uABI so it is safe + * to directly use them in the ABI. + * @flags: Flags for the file. Unused flag bits must be set to 0. * @nr_folios: Number of folios in the folios array. * @folios: KHO vmalloc descriptor pointing to the array of * struct memfd_luo_folio_ser. @@ -67,11 +81,13 @@ struct memfd_luo_folio_ser { struct memfd_luo_ser { u64 pos; u64 size; + u32 seals; + u32 flags; u64 nr_folios; struct kho_vmalloc folios; } __packed; /* The compatibility string for memfd file handler */ -#define MEMFD_LUO_FH_COMPATIBLE "memfd-v1" +#define MEMFD_LUO_FH_COMPATIBLE "memfd-v2" #endif /* _LINUX_KHO_ABI_MEMFD_H */ --- a/mm/memfd_luo.c~mm-memfd_luo-preserve-file-seals +++ a/mm/memfd_luo.c @@ -79,6 +79,8 @@ #include #include #include +#include + #include "internal.h" static int memfd_luo_preserve_folios(struct file *file, @@ -222,7 +224,7 @@ static int memfd_luo_preserve(struct liv struct memfd_luo_folio_ser *folios_ser; struct memfd_luo_ser *ser; u64 nr_folios; - int err = 0; + int err = 0, seals; inode_lock(inode); shmem_freeze(inode, true); @@ -234,8 +236,21 @@ static int memfd_luo_preserve(struct liv goto err_unlock; } + seals = memfd_get_seals(args->file); + if (seals < 0) { + err = seals; + goto err_free_ser; + } + + /* Make sure the file only has the seals supported by this version. */ + if (seals & ~MEMFD_LUO_ALL_SEALS) { + err = -EOPNOTSUPP; + goto err_free_ser; + } + ser->pos = args->file->f_pos; ser->size = i_size_read(inode); + ser->seals = seals; err = memfd_luo_preserve_folios(args->file, &ser->folios, &folios_ser, &nr_folios); @@ -449,13 +464,29 @@ static int memfd_luo_retrieve(struct liv if (!ser) return -EINVAL; - file = memfd_alloc_file("", 0); + /* Make sure the file only has seals supported by this version. */ + if (ser->seals & ~MEMFD_LUO_ALL_SEALS) { + err = -EOPNOTSUPP; + goto free_ser; + } + + /* + * The seals are preserved. Allow sealing here so they can be added + * later. + */ + file = memfd_alloc_file("", MFD_ALLOW_SEALING); if (IS_ERR(file)) { pr_err("failed to setup file: %pe\n", file); err = PTR_ERR(file); goto free_ser; } + err = memfd_add_seals(file, ser->seals); + if (err) { + pr_err("failed to add seals: %pe\n", ERR_PTR(err)); + goto put_file; + } + vfs_setpos(file, ser->pos, MAX_LFS_FILESIZE); file->f_inode->i_size = ser->size; _ Patches currently in -mm which might be from pratyush@kernel.org are liveupdate-luo_file-remember-retrieve-status.patch memfd-export-memfd_addget_seals.patch mm-memfd_luo-preserve-file-seals.patch