kernel/linux.git/fs/xattr.c, branch v7.1

xattr: support extended attributes on sockets

2026-03-02T10:06:42+00:00

Allow user.* extended attributes on sockets by adding S_IFSOCK to the xattr_permission() switch statement. Previously user.* xattrs were only permitted on regular files and directories. Symlinks and special files including sockets were rejected with -EPERM. Path-based AF_UNIX sockets have their inodes on the underlying filesystem (e.g. tmpfs) which already supports user.* xattrs through simple_xattrs. So for these the permission check was the only thing missing. For sockets in sockfs - everything created via socket() including abstract namespace AF_UNIX sockets - the preceding patch added simple_xattr storage with per-inode limits. With the permission check lifted here these sockets can now store user.* xattrs as well. This enables services to associate metadata with their sockets. For example, a service using Varlink for IPC can label its socket with user.varlink=1 allowing eBPF programs to selectively capture traffic and tools to discover IPC entrypoints by enumerating bound sockets via netlink. Similarly, protocol negotiation can be performed through xattrs such as indicating RFC 5424 structured syslog support on /dev/log. Link: https://patch.msgid.link/20260216-work-xattr-socket-v1-11-c2efa4f74cb7@kernel.org Acked-by: Darrick J. Wong Reviewed-by: Jan Kara Signed-off-by: Christian Brauner

xattr: move user limits for xattrs to generic infra

2026-03-02T10:06:42+00:00

Link: https://patch.msgid.link/20260216-work-xattr-socket-v1-9-c2efa4f74cb7@kernel.org Acked-by: Darrick J. Wong Signed-off-by: Christian Brauner

xattr: switch xattr_permission() to switch statement

2026-03-02T10:06:42+00:00

Simplify the codeflow by using a switch statement that switches on S_IFMT. Link: https://patch.msgid.link/20260216-work-xattr-socket-v1-8-c2efa4f74cb7@kernel.org Acked-by: Darrick J. Wong Reviewed-by: Jan Kara Signed-off-by: Christian Brauner

xattr: add xattr_permission_error()

2026-03-02T10:06:42+00:00

Stop repeating the ?: in multiple places and use a simple helper for this. Link: https://patch.msgid.link/20260216-work-xattr-socket-v1-7-c2efa4f74cb7@kernel.org Acked-by: Darrick J. Wong Reviewed-by: Jan Kara Signed-off-by: Christian Brauner

xattr: remove rbtree-based simple_xattr infrastructure

2026-03-02T10:06:42+00:00

Now that all consumers (shmem, kernfs, pidfs) have been converted to use the rhashtable-based simple_xattrs with pointer-based lazy allocation, remove the legacy rbtree code path. The rhashtable implementation provides O(1) average-case lookup with RCU-based lockless reads, replacing the O(log n) rbtree with reader-writer spinlock contention. Link: https://patch.msgid.link/20260216-work-xattr-socket-v1-6-c2efa4f74cb7@kernel.org Acked-by: Darrick J. Wong Signed-off-by: Christian Brauner

shmem: adapt to rhashtable-based simple_xattrs with lazy allocation

2026-02-23T12:06:38+00:00

Adapt tmpfs/shmem to use the rhashtable-based xattr path and switch from an embedded struct to pointer-based lazy allocation. Change shmem_inode_info.xattrs from embedded 'struct simple_xattrs' to a pointer 'struct simple_xattrs *', initialized to NULL. This avoids the rhashtable overhead for every tmpfs inode, which helps when a lot of inodes exist. The xattr store is allocated on first use: - shmem_initxattrs(): Allocates via simple_xattrs_alloc() when security modules set initial xattrs during inode creation. - shmem_xattr_handler_set(): Allocates on first setxattr, with a short-circuit for removal when no xattrs are stored yet. All read paths (shmem_xattr_handler_get, shmem_listxattr) check for NULL xattrs pointer and return -ENODATA or 0 respectively. Replaced xattr entries are freed via simple_xattr_free_rcu() to allow concurrent RCU readers to finish. shmem_evict_inode() conditionally frees the xattr store only when allocated. Also change simple_xattr_add() from void to int to propagate rhashtable insertion failures. shmem_initxattrs() is the only caller. Link: https://patch.msgid.link/20260216-work-xattr-socket-v1-3-c2efa4f74cb7@kernel.org Acked-by: Darrick J. Wong Reviewed-by: Jan Kara Signed-off-by: Christian Brauner

xattr: add rhashtable-based simple_xattr infrastructure

2026-02-23T12:06:38+00:00

Add rhashtable support to the simple_xattr subsystem while keeping the existing rbtree code fully functional. This allows consumers to be migrated one at a time without breaking any intermediate build. struct simple_xattrs gains a dispatch flag and a union holding either the rbtree (rb_root + rwlock) or rhashtable state: struct simple_xattrs { bool use_rhashtable; union { struct { struct rb_root rb_root; rwlock_t lock; }; struct rhashtable ht; }; }; simple_xattrs_init() continues to set up the rbtree path for existing embedded-struct callers. Add simple_xattrs_alloc() which dynamically allocates a simple_xattrs and initializes the rhashtable path. This is the entry point for consumers switching to pointer-based lazy allocation. The five core functions (get, set, list, add, free) dispatch based on the use_rhashtable flag. Existing callers continue to use the rbtree path unchanged. As each consumer is converted it will switch to simple_xattrs_alloc() and the rhashtable path. Once all consumers are converted a follow-up patch will remove the rbtree code. Link: https://patch.msgid.link/20260216-work-xattr-socket-v1-2-c2efa4f74cb7@kernel.org Acked-by: Darrick J. Wong Reviewed-by: Jan Kara Signed-off-by: Christian Brauner

xattr: add rcu_head and rhash_head to struct simple_xattr

2026-02-23T12:06:38+00:00

In preparation for converting simple_xattrs from rbtree to rhashtable, add rhash_head and rcu_head members to struct simple_xattr. The rhashtable implementation will use rhash_head for hash table linkage and RCU-based lockless reads, requiring that replaced or removed xattr entries be freed via call_rcu() rather than immediately. Add simple_xattr_free_rcu() which schedules RCU-deferred freeing of an xattr entry. This will be used by callers of simple_xattr_set() once they switch to the rhashtable-based xattr store. No functional changes. Link: https://patch.msgid.link/20260216-work-xattr-socket-v1-1-c2efa4f74cb7@kernel.org Acked-by: Darrick J. Wong Signed-off-by: Christian Brauner

filename_...xattr(): don't consume filename reference

2026-01-16T17:52:03+00:00

Callers switched to CLASS(filename_maybe_null) (in fs/xattr.c) and CLASS(filename_complete_delayed) (in io_uring/xattr.c). Signed-off-by: Al Viro

filelock: add struct delegated_inode

2025-11-12T08:38:34+00:00

The current API requires a pointer to an inode pointer. It's easy for callers to get this wrong. Add a new delegated_inode structure and use that to pass back any inode that needs to be waited on. Reviewed-by: Jan Kara Reviewed-by: NeilBrown Signed-off-by: Jeff Layton Link: https://patch.msgid.link/20251111-dir-deleg-ro-v6-3-52f3feebb2f2@kernel.org Signed-off-by: Christian Brauner