kernel/linux.git/mm/memfd.c, branch v6.19.11

memfd: export alloc_file()

2026-01-27T03:03:47+00:00

Patch series "mm: memfd_luo hotfixes". This series contains a couple of fixes for memfd preservation using LUO. This patch (of 3): The Live Update Orchestrator's (LUO) memfd preservation works by preserving all the folios of a memfd, re-creating an empty memfd on the next boot, and then inserting back the preserved folios. Currently it creates the file by directly calling shmem_file_setup(). This leaves out other work done by alloc_file() like setting up the file mode, flags, or calling the security hooks. Export alloc_file() to let memfd_luo use it. Rename it to memfd_alloc_file() since it is no longer private and thus needs a subsystem prefix. Link: https://lkml.kernel.org/r/20260122151842.4069702-1-pratyush@kernel.org Link: https://lkml.kernel.org/r/20260122151842.4069702-2-pratyush@kernel.org Signed-off-by: Pratyush Yadav (Google) Reviewed-by: Mike Rapoport (Microsoft) Reviewed-by: Pasha Tatashin Cc: Baolin Wang Cc: Hugh Dickins Signed-off-by: Andrew Morton

Merge tag 'selinux-pr-20251201' of git://git.kernel.org/pub/scm/linux/kernel/git/pcmoore/selinux

2025-12-03T18:45:47+00:00

Pull selinux updates from Paul Moore: - Improve the granularity of SELinux labeling for memfd files Currently when creating a memfd file, SELinux treats it the same as any other tmpfs, or hugetlbfs, file. While simple, the drawback is that it is not possible to differentiate between memfd and tmpfs files. This adds a call to the security_inode_init_security_anon() LSM hook and wires up SELinux to provide a set of memfd specific access controls, including the ability to control the execution of memfds. As usual, the commit message has more information. - Improve the SELinux AVC lookup performance Adopt MurmurHash3 for the SELinux AVC hash function instead of the custom hash function currently used. MurmurHash3 is already used for the SELinux access vector table so the impact to the code is minimal, and performance tests have shown improvements in both hash distribution and latency. See the commit message for the performance measurments. - Introduce a Kconfig option for the SELinux AVC bucket/slot size While we have the ability to grow the number of AVC hash buckets today, the size of the buckets (slot size) is fixed at 512. This pull request makes that slot size configurable at build time through a new Kconfig knob, CONFIG_SECURITY_SELINUX_AVC_HASH_BITS. * tag 'selinux-pr-20251201' of git://git.kernel.org/pub/scm/linux/kernel/git/pcmoore/selinux: selinux: improve bucket distribution uniformity of avc_hash() selinux: Move avtab_hash() to a shared location for future reuse selinux: Introduce a new config to make avc cache slot size adjustable memfd,selinux: call security_inode_init_security_anon()

Merge tag 'vfs-6.19-rc1.fd_prepare.fs' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs

2025-12-02T01:32:07+00:00

Pull fd prepare updates from Christian Brauner: "This adds the FD_ADD() and FD_PREPARE() primitive. They simplify the common pattern of get_unused_fd_flags() + create file + fd_install() that is used extensively throughout the kernel and currently requires cumbersome cleanup paths. FD_ADD() - For simple cases where a file is installed immediately: fd = FD_ADD(O_CLOEXEC, vfio_device_open_file(device)); if (fd < 0) vfio_device_put_registration(device); return fd; FD_PREPARE() - For cases requiring access to the fd or file, or additional work before publishing: FD_PREPARE(fdf, O_CLOEXEC, sync_file->file); if (fdf.err) { fput(sync_file->file); return fdf.err; } data.fence = fd_prepare_fd(fdf); if (copy_to_user((void __user *)arg, &data, sizeof(data))) return -EFAULT; return fd_publish(fdf); The primitives are centered around struct fd_prepare. FD_PREPARE() encapsulates all allocation and cleanup logic and must be followed by a call to fd_publish() which associates the fd with the file and installs it into the caller's fdtable. If fd_publish() isn't called, both are deallocated automatically. FD_ADD() is a shorthand that does fd_publish() immediately and never exposes the struct to the caller. I've implemented this in a way that it's compatible with the cleanup infrastructure while also being usable separately. IOW, it's centered around struct fd_prepare which is aliased to class_fd_prepare_t and so we can make use of all the basica guard infrastructure" * tag 'vfs-6.19-rc1.fd_prepare.fs' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs: (42 commits) io_uring: convert io_create_mock_file() to FD_PREPARE() file: convert replace_fd() to FD_PREPARE() vfio: convert vfio_group_ioctl_get_device_fd() to FD_ADD() tty: convert ptm_open_peer() to FD_ADD() ntsync: convert ntsync_obj_get_fd() to FD_PREPARE() media: convert media_request_alloc() to FD_PREPARE() hv: convert mshv_ioctl_create_partition() to FD_ADD() gpio: convert linehandle_create() to FD_PREPARE() pseries: port papr_rtas_setup_file_interface() to FD_ADD() pseries: convert papr_platform_dump_create_handle() to FD_ADD() spufs: convert spufs_gang_open() to FD_PREPARE() papr-hvpipe: convert papr_hvpipe_dev_create_handle() to FD_PREPARE() spufs: convert spufs_context_open() to FD_PREPARE() net/socket: convert __sys_accept4_file() to FD_ADD() net/socket: convert sock_map_fd() to FD_ADD() net/kcm: convert kcm_ioctl() to FD_PREPARE() net/handshake: convert handshake_nl_accept_doit() to FD_PREPARE() secretmem: convert memfd_secret() to FD_ADD() memfd: convert memfd_create() to FD_ADD() bpf: convert bpf_token_create() to FD_PREPARE() ...

memfd: convert memfd_create() to FD_ADD()

2025-11-28T11:42:34+00:00

Link: https://patch.msgid.link/20251123-work-fd-prepare-v4-25-b6efa1706cfd@kernel.org Signed-off-by: Christian Brauner

mm/memfd: fix information leak in hugetlb folios

2025-11-24T22:25:17+00:00

When allocating hugetlb folios for memfd, three initialization steps are missing: 1. Folios are not zeroed, leading to kernel memory disclosure to userspace 2. Folios are not marked uptodate before adding to page cache 3. hugetlb_fault_mutex is not taken before hugetlb_add_to_page_cache() The memfd allocation path bypasses the normal page fault handler (hugetlb_no_page) which would handle all of these initialization steps. This is problematic especially for udmabuf use cases where folios are pinned and directly accessed by userspace via DMA. Fix by matching the initialization pattern used in hugetlb_no_page(): - Zero the folio using folio_zero_user() which is optimized for huge pages - Mark it uptodate with folio_mark_uptodate() - Take hugetlb_fault_mutex before adding to page cache to prevent races The folio_zero_user() change also fixes a potential security issue where uninitialized kernel memory could be disclosed to userspace through read() or mmap() operations on the memfd. Link: https://lkml.kernel.org/r/20251112145034.2320452-1-kartikey406@gmail.com Fixes: 89c1905d9c14 ("mm/gup: introduce memfd_pin_folios() for pinning memfd folios") Signed-off-by: Deepanshu Kartikey Reported-by: syzbot+f64019ba229e3a5c411b@syzkaller.appspotmail.com Link: https://lore.kernel.org/all/20251112031631.2315651-1-kartikey406@gmail.com/ [v1] Closes: https://syzkaller.appspot.com/bug?extid=f64019ba229e3a5c411b Suggested-by: Oscar Salvador Suggested-by: David Hildenbrand Tested-by: syzbot+f64019ba229e3a5c411b@syzkaller.appspotmail.com Acked-by: Oscar Salvador Acked-by: David Hildenbrand (Red Hat) Acked-by: Hugh Dickins Cc: Vivek Kasireddy Cc: Jason Gunthorpe Cc: Jason Gunthorpe (v2) Cc: Christoph Hellwig (v6) Cc: Dave Airlie Cc: Gerd Hoffmann Cc: Signed-off-by: Andrew Morton

memfd,selinux: call security_inode_init_security_anon()

2025-10-22T23:28:27+00:00

Prior to this change, no security hooks were called at the creation of a memfd file. It means that, for SELinux as an example, it will receive the default type of the filesystem that backs the in-memory inode. In most cases, that would be tmpfs, but if MFD_HUGETLB is passed, it will be hugetlbfs. Both can be considered implementation details of memfd. It also means that it is not possible to differentiate between a file coming from memfd_create and a file coming from a standard tmpfs mount point. Additionally, no permission is validated at creation, which differs from the similar memfd_secret syscall. Call security_inode_init_security_anon during creation. This ensures that the file is setup similarly to other anonymous inodes. On SELinux, it means that the file will receive the security context of its task. The ability to limit fexecve on memfd has been of interest to avoid potential pitfalls where /proc/self/exe or similar would be executed [1][2]. Reuse the "execute_no_trans" and "entrypoint" access vectors, similarly to the file class. These access vectors may not make sense for the existing "anon_inode" class. Therefore, define and assign a new class "memfd_file" to support such access vectors. Guard these changes behind a new policy capability named "memfd_class". [1] https://crbug.com/1305267 [2] https://lore.kernel.org/lkml/20221215001205.51969-1-jeffxu@google.com/ Signed-off-by: Thiébaud Weksteen Reviewed-by: Stephen Smalley Tested-by: Stephen Smalley Acked-by: Hugh Dickins [PM: subj tweak] Signed-off-by: Paul Moore

mm/memfd: remove redundant casts

2025-09-21T21:22:00+00:00

MFD_ALL_FLAGS is already an unsigned int. Remove redundant casts to unsigned int. Link: https://lkml.kernel.org/r/efbbe6093b64a5b19f974871d5262d6e75dff2c0.1756639225.git.joeypabalinas@gmail.com Signed-off-by: Joey Pabalinas Cc: Baolin Wang Cc: Hugh Dickins Cc: Joey Pabalinas Signed-off-by: Andrew Morton

mm/memfd: replace deprecated strcpy() with memcpy() in alloc_name()

2025-07-20T01:59:57+00:00

strcpy() is deprecated; use memcpy() instead. Not copying the NUL terminator is safe because strncpy_from_user() would overwrite it anyway by appending uname to the destination buffer at index MFD_NAME_PREFIX_LEN. No functional changes intended. Link: https://github.com/KSPP/linux/issues/88 Link: https://lkml.kernel.org/r/20250712174516.64243-2-thorsten.blum@linux.dev Signed-off-by: Thorsten Blum Cc: Baolin Wang Cc: Hugh Dickins Signed-off-by: Andrew Morton

mm/memfd: reserve hugetlb folios before allocation

2025-07-10T05:42:15+00:00

When we try to allocate a folio via alloc_hugetlb_folio_reserve(), we need to ensure that there is an active reservation associated with the allocation. Otherwise, our allocation request would fail if there are no active reservations made at that moment against any other allocations. This is because alloc_hugetlb_folio_reserve() checks h->resv_huge_pages before proceeding with the allocation. Therefore, to address this issue, we just need to make a reservation (by calling hugetlb_reserve_pages()) before we try to allocate the folio. This will also ensure that proper region/subpool accounting is done associated with our allocation. Link: https://lkml.kernel.org/r/20250618053415.1036185-3-vivek.kasireddy@intel.com Signed-off-by: Vivek Kasireddy Cc: Steve Sistare Cc: Muchun Song Cc: David Hildenbrand Cc: Gerd Hoffmann Cc: Oscar Salvador Signed-off-by: Andrew Morton

mm: update core kernel code to use vm_flags_t consistently

2025-07-10T05:42:13+00:00

The core kernel code is currently very inconsistent in its use of vm_flags_t vs. unsigned long. This prevents us from changing the type of vm_flags_t in the future and is simply not correct, so correct this. While this results in rather a lot of churn, it is a critical pre-requisite for a future planned change to VMA flag type. Additionally, update VMA userland tests to account for the changes. To make review easier and to break things into smaller parts, driver and architecture-specific changes is left for a subsequent commit. The code has been adjusted to cascade the changes across all calling code as far as is needed. We will adjust architecture-specific and driver code in a subsequent patch. Overall, this patch does not introduce any functional change. Link: https://lkml.kernel.org/r/d1588e7bb96d1ea3fe7b9df2c699d5b4592d901d.1750274467.git.lorenzo.stoakes@oracle.com Signed-off-by: Lorenzo Stoakes Acked-by: Kees Cook Acked-by: Mike Rapoport (Microsoft) Acked-by: Jan Kara Acked-by: Christian Brauner Reviewed-by: Vlastimil Babka Acked-by: Oscar Salvador Reviewed-by: Pedro Falcato Acked-by: Zi Yan Acked-by: David Hildenbrand Reviewed-by: Anshuman Khandual Cc: Jann Horn Cc: Liam R. Howlett Cc: Catalin Marinas Cc: Jarkko Sakkinen Signed-off-by: Andrew Morton