security_inode_setxattr(9)

💖 security_inode_setxattr(9) 💖

okay bestie, welcome to the Kernel API Manual (yes that's the manual, we're in it, it's giving official ✨) — and today's main character is the little security hook that decides whether you're allowed to slap an extended attribute onto a file. it's a vibe check for xattrs, basically. let's get into it 🎀

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✨ SYNOPSIS ✨

int security_inode_setxattr (struct mnt_idmap *idmap , struct dentry
*dentry , const char *name , const void *value , size_t size , int flags
);

like, she takes a whole little friend group of arguments. all of them. none of them are optional, don't even try 🙈

---

🦋 ARGUMENTS 🦋

• idmap — the idmap of the mount. she's mapping the ids, that's literally her whole thing 💅
• dentry — the file. THE file. the one we're talking about 🫶
• name — the xattr name 🌸
• value — the xattr value 💜
• size — the size of the xattr value, important, do not skip, i'm serious 📏
• flags — flags. yes. that's the description. flags 🎀

---

🌈 DESCRIPTION 🌈

so, this hook does the permission checks that need doing before the extended attributes (xattrs) get set on dentry. simple enough right? wrong. because there's ✨ lore ✨.

it's important to note — and i mean genuinely, don't skim this part — that we have some additional logic that runs before the main LSM implementation calls, and its whole job is to detect whether we need to perform an additional capability check at the LSM layer. it's a pre-check for the check, ok? she's thorough.

normally we enforce a capability check prior to executing the various LSM hook implementations. so: capability check first, LSM hooks after. that's the standard order, that's the routine, that's the choreography 🩰

but! if a LSM wants to avoid this capability check, it can register a inode_xattr_skipcap hook and return a value of 1 for the xattrs it wants to avoid the capability check on. and when it does that, it is leaving the LSM fully responsible for enforcing the access control for that specific xattr. like, fully. the whole thing. all of it. she's on her own now, no safety net, no cap 👑

if all of the enabled LSMs refrain from registering a inode_xattr_skipcap hook, or return a 0 (that's the default return value, fyi), then the capability check is still performed. and if no inode_xattr_skipcap hooks are registered at all? capability check is performed. periodt 💀

ngl the 0-vs-1 thing is the whole plot here — 1 means "i got this, skip the cap check," 0 (or nothing registered at all) means the capability check goes ahead. no cap, no skip. iykyk 🧚

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🔥 RETURN 🔥

Returns 0 if permission is granted. that's it. that's the good ending ⭐

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👑 SEE ALSO 👑

okay this is the part where she lists literally everyone she knows. and bestie, she knows everyone. the whole ./security family reunion, plus one very specific file. here's the entire guest list, no plus-ones omitted 💖

Kernel file ./security/security.c lsm_file_alloc(9),
lsm_backing_file_alloc(9), lsm_blob_alloc(9), lsm_cred_alloc(9),
lsm_inode_alloc(9), lsm_task_alloc(9), lsm_ipc_alloc(9),
lsm_key_alloc(9), lsm_msg_msg_alloc(9), lsm_bdev_alloc(9),
lsm_bpf_map_alloc(9), lsm_bpf_prog_alloc(9), lsm_bpf_token_alloc(9),
lsm_superblock_alloc(9), lsm_fill_user_ctx(9),
security_binder_set_context_mgr(9), security_binder_transaction(9),
security_binder_transfer_binder(9), security_binder_transfer_file(9),
security_ptrace_access_check(9), security_ptrace_traceme(9),
security_capget(9), security_capset(9), security_capable(9),
security_quotactl(9), security_quota_on(9), security_syslog(9),
security_settime64(9), security_vm_enough_memory_mm(9),
security_bprm_creds_for_exec(9), security_bprm_creds_from_file(9),
security_bprm_check(9), security_bprm_committing_creds(9),
security_bprm_committed_creds(9), security_fs_context_submount(9),
security_fs_context_dup(9), security_fs_context_parse_param(9),
security_sb_alloc(9), security_sb_delete(9), security_sb_free(9),
security_free_mnt_opts(9), security_sb_eat_lsm_opts(9),
security_sb_mnt_opts_compat(9), security_sb_remount(9),
security_sb_kern_mount(9), security_sb_show_options(9),
security_sb_statfs(9), security_sb_mount(9), security_sb_umount(9),
security_sb_pivotroot(9), security_sb_set_mnt_opts(9),
security_sb_clone_mnt_opts(9), security_move_mount(9),
security_path_notify(9), security_inode_alloc(9),
security_inode_free(9), security_dentry_init_security(9),
security_dentry_create_files_as(9), security_inode_init_security(9),
security_inode_init_security_anon(9), security_path_mknod(9),
security_path_post_mknod(9), security_path_mkdir(9),
security_path_rmdir(9), security_path_unlink(9),
security_path_symlink(9), security_path_link(9),
security_path_rename(9), security_path_truncate(9),
security_path_chmod(9), security_path_chown(9), security_path_chroot(9),
security_inode_create(9), security_inode_post_create_tmpfile(9),
security_inode_link(9), security_inode_unlink(9),
security_inode_symlink(9), security_inode_mkdir(9),
security_inode_rmdir(9), security_inode_mknod(9),
security_inode_rename(9), security_inode_readlink(9),
security_inode_follow_link(9), security_inode_permission(9),
security_inode_setattr(9), security_inode_post_setattr(9),
security_inode_getattr(9), security_inode_set_acl(9),
security_inode_post_set_acl(9), security_inode_get_acl(9),
security_inode_remove_acl(9), security_inode_post_remove_acl(9),
security_inode_post_setxattr(9), security_inode_getxattr(9),
security_inode_listxattr(9), security_inode_removexattr(9),
security_inode_post_removexattr(9), security_inode_file_setattr(9),
security_inode_file_getattr(9), security_inode_need_killpriv(9),
security_inode_killpriv(9), security_inode_getsecurity(9),
security_inode_setsecurity(9), security_inode_listsecurity(9),
security_inode_getlsmprop(9), security_inode_copy_up(9),
security_inode_copy_up_xattr(9), security_inode_setintegrity(9),
security_kernfs_init_security(9), security_file_permission(9),
security_file_alloc(9), security_file_release(9), security_file_free(9),
security_backing_file_alloc(9), security_backing_file_free(9),
security_file_ioctl(9), security_file_ioctl_compat(9),
security_mmap_file(9), security_mmap_backing_file(9),
security_mmap_addr(9), security_file_mprotect(9), security_file_lock(9),
security_file_fcntl(9), security_file_set_fowner(9),
security_file_send_sigiotask(9), security_file_receive(9),
security_file_open(9), security_file_post_open(9),
security_file_truncate(9), security_task_alloc(9),
security_task_free(9), security_cred_alloc_blank(9),
security_cred_free(9), security_prepare_creds(9),
security_transfer_creds(9), security_cred_getsecid(9),
security_cred_getlsmprop(9), security_kernel_act_as(9),
security_kernel_create_files_as(9), security_kernel_module_request(9),
security_kernel_read_file(9), security_kernel_post_read_file(9),
security_kernel_load_data(9), security_kernel_post_load_data(9),
security_task_fix_setuid(9), security_task_fix_setgid(9),
security_task_fix_setgroups(9), security_task_setpgid(9),
security_task_getpgid(9), security_task_getsid(9),
security_current_getlsmprop_subj(9), security_task_getlsmprop_obj(9),
security_task_setnice(9), security_task_setioprio(9),
security_task_getioprio(9), security_task_prlimit(9),
security_task_setrlimit(9), security_task_setscheduler(9),
security_task_getscheduler(9), security_task_movememory(9),
security_task_kill(9), security_task_prctl(9),
security_task_to_inode(9), security_create_user_ns(9),
security_ipc_permission(9), security_ipc_getlsmprop(9),
security_msg_msg_alloc(9), security_msg_msg_free(9),
security_msg_queue_alloc(9), security_msg_queue_free(9),
security_msg_queue_associate(9), security_msg_queue_msgctl(9),
security_msg_queue_msgsnd(9), security_msg_queue_msgrcv(9),
security_shm_alloc(9), security_shm_free(9), security_shm_associate(9),
security_shm_shmctl(9), security_shm_shmat(9), security_sem_alloc(9),
security_sem_free(9), security_sem_associate(9), security_sem_semctl(9),
security_sem_semop(9), security_d_instantiate(9),
security_getselfattr(9), security_setselfattr(9),
security_getprocattr(9), security_setprocattr(9),
security_ismaclabel(9), security_secid_to_secctx(9),
security_lsmprop_to_secctx(9), security_secctx_to_secid(9),
security_release_secctx(9), security_inode_invalidate_secctx(9),
security_inode_notifysecctx(9), security_inode_setsecctx(9),
security_inode_getsecctx(9), security_post_notification(9),
security_watch_key(9), security_netlink_send(9),
security_unix_stream_connect(9), security_unix_may_send(9),
security_socket_create(9), security_socket_post_create(9),
security_socket_socketpair(9), security_socket_bind(9),
security_socket_connect(9), security_socket_listen(9),
security_socket_accept(9), security_socket_sendmsg(9),
security_socket_recvmsg(9), security_socket_getsockname(9),
security_socket_getpeername(9), security_socket_getsockopt(9),
security_socket_setsockopt(9), security_socket_shutdown(9),
security_sock_rcv_skb(9), security_socket_getpeersec_stream(9),
security_socket_getpeersec_dgram(9), lsm_sock_alloc(9),
security_sk_alloc(9), security_sk_free(9), security_sk_clone(9),
security_sk_classify_flow(9), security_req_classify_flow(9),
security_sock_graft(9), security_inet_conn_request(9),
security_inet_csk_clone(9), security_inet_conn_established(9),
security_secmark_relabel_packet(9), security_secmark_refcount_inc(9),
security_secmark_refcount_dec(9), security_tun_dev_alloc_security(9),
security_tun_dev_free_security(9), security_tun_dev_create(9),
security_tun_dev_attach_queue(9), security_tun_dev_attach(9),
security_tun_dev_open(9), security_sctp_assoc_request(9),
security_sctp_bind_connect(9), security_sctp_sk_clone(9),
security_sctp_assoc_established(9), security_mptcp_add_subflow(9),
security_unix_find(9), security_ib_pkey_access(9),
security_ib_endport_manage_subnet(9), security_ib_alloc_security(9),
security_ib_free_security(9), security_xfrm_policy_alloc(9),
security_xfrm_policy_clone(9), security_xfrm_policy_free(9),
security_xfrm_policy_delete(9), security_xfrm_state_alloc(9),
security_xfrm_state_alloc_acquire(9), security_xfrm_state_delete(9),
security_xfrm_state_free(9), security_xfrm_policy_lookup(9),
security_xfrm_state_pol_flow_match(9), security_xfrm_decode_session(9),
security_key_alloc(9), security_key_free(9), security_key_permission(9),
security_key_getsecurity(9), security_key_post_create_or_update(9),
security_audit_rule_init(9), security_audit_rule_known(9),
security_audit_rule_free(9), security_audit_rule_match(9),
security_bpf(9), security_bpf_map(9), security_bpf_prog(9),
security_bpf_map_create(9), security_bpf_prog_load(9),
security_bpf_token_create(9), security_bpf_token_cmd(9),
security_bpf_token_capable(9), security_bpf_map_free(9),
security_bpf_prog_free(9), security_bpf_token_free(9),
security_locked_down(9), security_bdev_alloc(9), security_bdev_free(9),
security_bdev_setintegrity(9), security_perf_event_open(9),
security_perf_event_alloc(9), security_perf_event_free(9),
security_perf_event_read(9), security_perf_event_write(9),
security_uring_override_creds(9), security_uring_sqpoll(9),
security_uring_cmd(9), security_uring_allowed(9),
security_initramfs_populated(9)

like… she said "let me just tag everyone" and then actually did it. iconic behavior honestly 🌟

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aaaand that's the page, bestie!! 🌸 this one dropped from ./security in October 2026, so if you're reading it in a future where xattrs are solved, tell me everything. mwah, go set some attributes responsibly 💅🎀🫶