inode_permission(9)

💅 inode_permission(9) — the kernel API manual page, bestie edition ✨

Okay so welcome to inode_permission(9), straight out of the Kernel API Manual. Yes, that's a section 9 page, and yes, it's giving "kernel dev at 2am drinking iced coffee" energy. Buckle up 🎀

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✨ NAME ✨

inode_permission — check for access rights to a given inode 🦋

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🌸 SYNOPSIS 🌸

int inode_permission (struct mnt_idmap *idmap , struct inode *inode ,
int mask );

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💖 ARGUMENTS 💖

• idmap — the idmap of the mount that the inode was found from. literally the mapping context, she's the one who knows the vibes of the mount 👑
• inode — the inode you wanna check permission on. the main character, no cap 💅
• mask — the right you're checking for: MAY_READ, MAY_WRITE, MAY_EXEC 🔥

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🦋 DESCRIPTION 🦋

So basically, this bad boy checks for read/write/execute permissions on an inode. iconic behaviour honestly.

The way it does it: we use fs[ug]id for this, which lets us set arbitrary permissions for filesystem access without changing the "normal" UIDs which are used for other things. which is lowkey genius 🧚

⚠️ Heads up bestie: when checking for MAY_APPEND, MAY_WRITE must also be set in mask. like, both. not one. both. fr fr 😭

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🌈 SEE ALSO 🌈

Kernel file ./fs/namei.c — and omg the friend group here is huge, she knows everyone:

• check_acl(9), acl_permission_check(9), generic_permission(9), do_inode_permission(9), sb_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_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)

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okay that's the whole page, you ate that 🫶 this listing comes from ./fs, October 2026, and it's inode_permission(9) — go forth and check those permissions, bestie 💜✨