kernel/linux.git/fs/namespace.c, branch v7.0-rc7

Merge tag 'vfs-7.0-rc2.fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs

2026-02-25T18:34:23+00:00

Pull vfs fixes from Christian Brauner: - Fix an uninitialized variable in file_getattr(). The flags_valid field wasn't initialized before calling vfs_fileattr_get(), triggering KMSAN uninit-value reports in fuse - Fix writeback wakeup and logging timeouts when DETECT_HUNG_TASK is not enabled. sysctl_hung_task_timeout_secs is 0 in that case causing spurious "waiting for writeback completion for more than 1 seconds" warnings - Fix a null-ptr-deref in do_statmount() when the mount is internal - Add missing kernel-doc description for the @private parameter in iomap_readahead() - Fix mount namespace creation to hold namespace_sem across the mount copy in create_new_namespace(). The previous drop-and-reacquire pattern was fragile and failed to clean up mount propagation links if the real rootfs was a shared or dependent mount - Fix /proc mount iteration where m->index wasn't updated when m->show() overflows, causing a restart to repeatedly show the same mount entry in a rapidly expanding mount table - Return EFSCORRUPTED instead of ENOSPC in minix_new_inode() when the inode number is out of range - Fix unshare(2) when CLONE_NEWNS is set and current->fs isn't shared. copy_mnt_ns() received the live fs_struct so if a subsequent namespace creation failed the rollback would leave pwd and root pointing to detached mounts. Always allocate a new fs_struct when CLONE_NEWNS is requested - fserror bug fixes: - Remove the unused fsnotify_sb_error() helper now that all callers have been converted to fserror_report_metadata - Fix a lockdep splat in fserror_report() where igrab() takes inode::i_lock which can be held in IRQ context. Replace igrab() with a direct i_count bump since filesystems should not report inodes that are about to be freed or not yet exposed - Handle error pointer in procfs for try_lookup_noperm() - Fix an integer overflow in ep_loop_check_proc() where recursive calls returning INT_MAX would overflow when +1 is added, breaking the recursion depth check - Fix a misleading break in pidfs * tag 'vfs-7.0-rc2.fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs: pidfs: avoid misleading break eventpoll: Fix integer overflow in ep_loop_check_proc() proc: Fix pointer error dereference fserror: fix lockdep complaint when igrabbing inode fsnotify: drop unused helper unshare: fix unshare_fs() handling minix: Correct errno in minix_new_inode namespace: fix proc mount iteration mount: hold namespace_sem across copy in create_new_namespace() iomap: Describe @private in iomap_readahead() statmount: Fix the null-ptr-deref in do_statmount() writeback: Fix wakeup and logging timeouts for !DETECT_HUNG_TASK fs: init flags_valid before calling vfs_fileattr_get

Convert 'alloc_obj' family to use the new default GFP_KERNEL argument

2026-02-22T01:09:51+00:00

This was done entirely with mindless brute force, using git grep -l '\

treewide: Replace kmalloc with kmalloc_obj for non-scalar types

2026-02-21T09:02:28+00:00

This is the result of running the Coccinelle script from scripts/coccinelle/api/kmalloc_objs.cocci. The script is designed to avoid scalar types (which need careful case-by-case checking), and instead replace kmalloc-family calls that allocate struct or union object instances: Single allocations: kmalloc(sizeof(TYPE), ...) are replaced with: kmalloc_obj(TYPE, ...) Array allocations: kmalloc_array(COUNT, sizeof(TYPE), ...) are replaced with: kmalloc_objs(TYPE, COUNT, ...) Flex array allocations: kmalloc(struct_size(PTR, FAM, COUNT), ...) are replaced with: kmalloc_flex(*PTR, FAM, COUNT, ...) (where TYPE may also be *VAR) The resulting allocations no longer return "void *", instead returning "TYPE *". Signed-off-by: Kees Cook

namespace: fix proc mount iteration

2026-02-18T13:04:42+00:00

The m->index isn't updated when m->show() overflows and retains its value before the current mount causing a restart to start at the same value. If that happens in short order to due a quickly expanding mount table this would cause the same mount to be shown again and again. Ensure that *pos always equals the mount id of the mount that was returned by start/next. On restart after overflow mnt_find_id_at(*pos) finds the exact mount. This should avoid duplicates, avoid skips and should handle concurrent modification just fine. Cc: Fixed: 2eea9ce4310d8 ("mounts: keep list of mounts in an rbtree") Link: https://patch.msgid.link/20260129-geleckt-treuhand-4bb940acacd9@brauner Signed-off-by: Christian Brauner

mount: hold namespace_sem across copy in create_new_namespace()

2026-02-18T13:04:42+00:00

Fix an oversight when creating a new mount namespace. If someone had the bright idea to make the real rootfs a shared or dependent mount and it is later copied the copy will become a peer of the old real rootfs mount or a dependent mount of it. The namespace semaphore is dropped and we use mount lock exact to lock the new real root mount. If that fails or the subsequent do_loopback() fails we rely on the copy of the real root mount to be cleaned up by path_put(). The problem is that this doesn't deal with mount propagation and will leave the mounts linked in the propagation lists. When creating a new mount namespace create_new_namespace() first acquires namespace_sem to clone the nullfs root, drops it, then reacquires it via LOCK_MOUNT_EXACT which takes inode_lock first to respect the inode_lock -> namespace_sem lock ordering. This drop-and-reacquire pattern is fragile and was the source of the propagation cleanup bug fixed in the preceding commit. Extend lock_mount_exact() with a copy_mount mode that clones the mount under the locks atomically. When copy_mount is true, path_overmounted() is skipped since we're copying the mount, not mounting on top of it - the nullfs root always has rootfs mounted on top so the check would always fail. If clone_mnt() fails after get_mountpoint() has pinned the mountpoint, __unlock_mount() is used to properly unpin the mountpoint and release both locks. This allows create_new_namespace() to use LOCK_MOUNT_EXACT_COPY which takes inode_lock and namespace_sem once and holds them throughout the clone and subsequent mount operations, eliminating the drop-and-reacquire pattern entirely. Reported-by: syzbot+a89f9434fb5a001ccd58@syzkaller.appspotmail.com Fixes: 9b8a0ba68246 ("mount: add OPEN_TREE_NAMESPACE") # mainline only Link: https://lore.kernel.org/699047f6.050a0220.2757fb.0024.GAE@google.com Signed-off-by: Christian Brauner

statmount: Fix the null-ptr-deref in do_statmount()

2026-02-14T12:17:50+00:00

If the mount is internal, it's mnt_ns will be MNT_NS_INTERNAL, which is defined as ERR_PTR(-EINVAL). So, in the do_statmount(), need to check ns of mount by IS_ERR() and return. Fixes: 0e5032237ee5 ("statmount: accept fd as a parameter") Reported-by: syzbot+9e03a9535ea65f687a44@syzkaller.appspotmail.com Closes: https://lore.kernel.org/all/698e287a.a70a0220.2c38d7.009e.GAE@google.com/ Signed-off-by: Qing Wang Link: https://patch.msgid.link/20260213103006.2472569-1-wangqing7171@gmail.com Reviewed-by: Bhavik Sachdev Signed-off-by: Christian Brauner

Merge tag 'pull-filename' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs

2026-02-10T00:58:28+00:00

Pull vfs 'struct filename' updates from Al Viro: "[Mostly] sanitize struct filename handling" * tag 'pull-filename' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs: (68 commits) sysfs(2): fs_index() argument is _not_ a pathname alpha: switch osf_mount() to strndup_user() ksmbd: use CLASS(filename_kernel) mqueue: switch to CLASS(filename) user_statfs(): switch to CLASS(filename) statx: switch to CLASS(filename_maybe_null) quotactl_block(): switch to CLASS(filename) chroot(2): switch to CLASS(filename) move_mount(2): switch to CLASS(filename_maybe_null) namei.c: switch user pathname imports to CLASS(filename{,_flags}) namei.c: convert getname_kernel() callers to CLASS(filename_kernel) do_f{chmod,chown,access}at(): use CLASS(filename_uflags) do_readlinkat(): switch to CLASS(filename_flags) do_sys_truncate(): switch to CLASS(filename) do_utimes_path(): switch to CLASS(filename_uflags) chdir(2): unspaghettify a bit... do_fchownat(): unspaghettify a bit... fspick(2): use CLASS(filename_flags) name_to_handle_at(): use CLASS(filename_uflags) vfs_open_tree(): use CLASS(filename_uflags) ...

Merge tag 'vfs-7.0-rc1.misc' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs

2026-02-09T23:13:05+00:00

Pull misc vfs updates from Christian Brauner: "This contains a mix of VFS cleanups, performance improvements, API fixes, documentation, and a deprecation notice. Scalability and performance: - Rework pid allocation to only take pidmap_lock once instead of twice during alloc_pid(), improving thread creation/teardown throughput by 10-16% depending on false-sharing luck. Pad the namespace refcount to reduce false-sharing - Track file lock presence via a flag in ->i_opflags instead of reading ->i_flctx, avoiding false-sharing with ->i_readcount on open/close hot paths. Measured 4-16% improvement on 24-core open-in-a-loop benchmarks - Use a consume fence in locks_inode_context() to match the store-release/load-consume idiom, eliminating a hardware fence on some architectures - Annotate cdev_lock with __cacheline_aligned_in_smp to prevent false-sharing - Remove a redundant DCACHE_MANAGED_DENTRY check in __follow_mount_rcu() that never fires since the caller already verifies it, eliminating a 100% mispredicted branch - Fix a 100% mispredicted likely() in devcgroup_inode_permission() that became wrong after a prior code reorder Bug fixes and correctness: - Make insert_inode_locked() wait for inode destruction instead of skipping, fixing a corner case where two matching inodes could exist in the hash - Move f_mode initialization before file_ref_init() in alloc_file() to respect the SLAB_TYPESAFE_BY_RCU ordering contract - Add a WARN_ON_ONCE guard in try_to_free_buffers() for folios with no buffers attached, preventing a null pointer dereference when AS_RELEASE_ALWAYS is set but no release_folio op exists - Fix select restart_block to store end_time as timespec64, avoiding truncation of tv_sec on 32-bit architectures - Make dump_inode() use get_kernel_nofault() to safely access inode and superblock fields, matching the dump_mapping() pattern API modernization: - Make posix_acl_to_xattr() allocate the buffer internally since every single caller was doing it anyway. Reduces boilerplate and unnecessary error checking across ~15 filesystems - Replace deprecated simple_strtoul() with kstrtoul() for the ihash_entries, dhash_entries, mhash_entries, and mphash_entries boot parameters, adding proper error handling - Convert chardev code to use guard(mutex) and __free(kfree) cleanup patterns - Replace min_t() with min() or umin() in VFS code to avoid silently truncating unsigned long to unsigned int - Gate LOOKUP_RCU assertions behind CONFIG_DEBUG_VFS since callers already check the flag Deprecation: - Begin deprecating legacy BSD process accounting (acct(2)). The interface has numerous footguns and better alternatives exist (eBPF) Documentation: - Fix and complete kernel-doc for struct export_operations, removing duplicated documentation between ReST and source - Fix kernel-doc warnings for __start_dirop() and ilookup5_nowait() Testing: - Add a kunit test for initramfs cpio handling of entries with filesize > PATH_MAX Misc: - Add missing include in fs_struct.c" * tag 'vfs-7.0-rc1.misc' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs: (28 commits) posix_acl: make posix_acl_to_xattr() alloc the buffer fs: make insert_inode_locked() wait for inode destruction initramfs_test: kunit test for cpio.filesize > PATH_MAX fs: improve dump_inode() to safely access inode fields fs: add for 'init_fs' docs: exportfs: Use source code struct documentation fs: move initializing f_mode before file_ref_init() exportfs: Complete kernel-doc for struct export_operations exportfs: Mark struct export_operations functions at kernel-doc exportfs: Fix kernel-doc output for get_name() acct(2): begin the deprecation of legacy BSD process accounting device_cgroup: remove branch hint after code refactor VFS: fix __start_dirop() kernel-doc warnings fs: Describe @isnew parameter in ilookup5_nowait() fs/namei: Remove redundant DCACHE_MANAGED_DENTRY check in __follow_mount_rcu fs: only assert on LOOKUP_RCU when built with CONFIG_DEBUG_VFS select: store end_time as timespec64 in restart block chardev: Switch to guard(mutex) and __free(kfree) namespace: Replace simple_strtoul with kstrtoul to parse boot params dcache: Replace simple_strtoul with kstrtoul in set_dhash_entries ...

Merge tag 'vfs-7.0-rc1.namespace' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs

2026-02-09T22:43:47+00:00

Pull vfs mount updates from Christian Brauner: - statmount: accept fd as a parameter Extend struct mnt_id_req with a file descriptor field and a new STATMOUNT_BY_FD flag. When set, statmount() returns mount information for the mount the fd resides on — including detached mounts (unmounted via umount2(MNT_DETACH)). For detached mounts the STATMOUNT_MNT_POINT and STATMOUNT_MNT_NS_ID mask bits are cleared since neither is meaningful. The capability check is skipped for STATMOUNT_BY_FD since holding an fd already implies prior access to the mount and equivalent information is available through fstatfs() and /proc/pid/mountinfo without privilege. Includes comprehensive selftests covering both attached and detached mount cases. - fs: Remove internal old mount API code (1 patch) Now that every in-tree filesystem has been converted to the new mount API, remove all the legacy shim code in fs_context.c that handled unconverted filesystems. This deletes ~280 lines including legacy_init_fs_context(), the legacy_fs_context struct, and associated wrappers. The mount(2) syscall path for userspace remains untouched. Documentation references to the legacy callbacks are cleaned up. - mount: add OPEN_TREE_NAMESPACE to open_tree() Container runtimes currently use CLONE_NEWNS to copy the caller's entire mount namespace — only to then pivot_root() and recursively unmount everything they just copied. With large mount tables and thousands of parallel container launches this creates significant contention on the namespace semaphore. OPEN_TREE_NAMESPACE copies only the specified mount tree (like OPEN_TREE_CLONE) but returns a mount namespace fd instead of a detached mount fd. The new namespace contains the copied tree mounted on top of a clone of the real rootfs. This functions as a combined unshare(CLONE_NEWNS) + pivot_root() in a single syscall. Works with user namespaces: an unshare(CLONE_NEWUSER) followed by OPEN_TREE_NAMESPACE creates a mount namespace owned by the new user namespace. Mount namespace file mounts are excluded from the copy to prevent cycles. Includes ~1000 lines of selftests" * tag 'vfs-7.0-rc1.namespace' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs: selftests/open_tree: add OPEN_TREE_NAMESPACE tests mount: add OPEN_TREE_NAMESPACE fs: Remove internal old mount API code selftests: statmount: tests for STATMOUNT_BY_FD statmount: accept fd as a parameter statmount: permission check should return EPERM

mount: add OPEN_TREE_NAMESPACE

2026-01-16T18:21:40+00:00

When creating containers the setup usually involves using CLONE_NEWNS via clone3() or unshare(). This copies the caller's complete mount namespace. The runtime will also assemble a new rootfs and then use pivot_root() to switch the old mount tree with the new rootfs. Afterward it will recursively umount the old mount tree thereby getting rid of all mounts. On a basic system here where the mount table isn't particularly large this still copies about 30 mounts. Copying all of these mounts only to get rid of them later is pretty wasteful. This is exacerbated if intermediary mount namespaces are used that only exist for a very short amount of time and are immediately destroyed again causing a ton of mounts to be copied and destroyed needlessly. With a large mount table and a system where thousands or ten-thousands of containers are spawned in parallel this quickly becomes a bottleneck increasing contention on the semaphore. Extend open_tree() with a new OPEN_TREE_NAMESPACE flag. Similar to OPEN_TREE_CLONE only the indicated mount tree is copied. Instead of returning a file descriptor referring to that mount tree OPEN_TREE_NAMESPACE will cause open_tree() to return a file descriptor to a new mount namespace. In that new mount namespace the copied mount tree has been mounted on top of a copy of the real rootfs. The caller can setns() into that mount namespace and perform any additionally required setup such as move_mount() detached mounts in there. This allows OPEN_TREE_NAMESPACE to function as a combined unshare(CLONE_NEWNS) and pivot_root(). A caller may for example choose to create an extremely minimal rootfs: fd_mntns = open_tree(-EBADF, "/var/lib/containers/wootwoot", OPEN_TREE_NAMESPACE); This will create a mount namespace where "wootwoot" has become the rootfs mounted on top of the real rootfs. The caller can now setns() into this new mount namespace and assemble additional mounts. This also works with user namespaces: unshare(CLONE_NEWUSER); fd_mntns = open_tree(-EBADF, "/var/lib/containers/wootwoot", OPEN_TREE_NAMESPACE); which creates a new mount namespace owned by the earlier created user namespace with "wootwoot" as the rootfs mounted on top of the real rootfs. Link: https://patch.msgid.link/20251229-work-empty-namespace-v1-1-bfb24c7b061f@kernel.org Tested-by: Jeff Layton Reviewed-by: Aleksa Sarai Reviewed-by: Jeff Layton Suggested-by: Christian Brauner Suggested-by: Aleksa Sarai Signed-off-by: Christian Brauner