lookup_noperm(9)

💅 lookup_noperm(9) — yes bestie, we're reading a kernel API manual page today

okay so real talk, this one lives in the Kernel API Manual (section 9, the "kernel internals" girlies) and it's about looking up exactly one pathname component without doing any permission checks. it's giving "trust me bro, the caller already checked." let's get into it ✨

🌸 NAME 🌸

lookup_noperm — the filesystem helper that looks up a single pathname component 🎀

🦋 SYNOPSIS 🦋

struct dentry * lookup_noperm (struct qstr *name , struct dentry *base );

✨ ARGUMENTS ✨

• name — a qstr holding the pathname component you wanna look up 💖
• base — the base directory you're looking up from 🌸

👑 DESCRIPTION 👑

okay so first thing, and I need you to hear me on this one: this routine is purely a helper for filesystem usage and it should not be called by generic code. like, it's not for everyone, it's not a public vibe, it's fs-internal only 🙈

and the headline: it does no permission checking. none. zero. not a single check. it's literally in the name, bestie 💀

🚨 Also the caller MUST hold base->i_rwsem. No ifs, no buts, no "well I thought—". You hold it. That's the whole deal. 🚨

🫶 SEE ALSO 🫶

Kernel file ./fs/namei.c, plus the entire extended universe of friends, because this page's SEE ALSO is lowkey a group chat with 58 members and we are NOT leaving anybody out 👑

• check_acl(9)
• acl_permission_check(9)
• generic_permission(9)
• do_inode_permission(9)
• sb_permission(9)
• inode_permission(9)
• path_get(9)
• path_put(9)
• path_connected(9)
• try_to_unlazy(9)
• try_to_unlazy_next(9)
• complete_walk(9)
• may_follow_link(9)
• safe_hardlink_source(9)
• may_linkat(9)
• may_create_in_sticky(9)
• lookup_fast(9)
• start_dirop(9)
• end_dirop(9)
• kern_path_parent(9)
• vfs_path_parent_lookup(9)
• vfs_path_lookup(9)
• try_lookup_noperm(9)
• lookup_one(9)
• lookup_one_unlocked(9)
• lookup_one_positive_killable(9)
• lookup_one_positive_unlocked(9)
• lookup_noperm_unlocked(9)
• start_creating(9)
• start_removing(9)
• start_creating_killable(9)
• start_removing_killable(9)
• start_creating_noperm(9)
• start_removing_noperm(9)
• start_creating_dentry(9)
• start_removing_dentry(9)
• __start_renaming(9)
• start_renaming(9)
• start_renaming_dentry(9)
• start_renaming_two_dentries(9)
• vfs_prepare_mode(9)
• vfs_create(9)
• atomic_open(9)
• vfs_lookup_open(9)
• vfs_tmpfile(9)
• kernel_tmpfile_open(9)
• end_creating_path(9)
• dentry_create(9)
• vfs_mknod(9)
• vfs_mkdir(9)
• vfs_rmdir(9)
• vfs_unlink(9)
• vfs_symlink(9)
• vfs_link(9)
• vfs_rename(9)
• vfs_readlink(9)
• vfs_get_link(9)
• page_get_link(9)
• page_put_link(9)

that's the whole page, periodt 💜 this icon dropped from ./fs in October 2026 and honestly? she ate. go hold that i_rwsem and slay 🧚✨