posix_acl_chmod(9)

🌸 posix_acl_chmod(9) 🌸

okay bestie, welcome to the Kernel API Manual corner of the group chat 🫶 — this is the page for posix_acl_chmod, and it's literally about chmod-ing a posix acl. no cap.

💖 NAME 💖

posix_acl_chmod — chmod a posix acl. that's the whole name, and it ate 💅

✨ SYNOPSIS ✨

       int  posix_acl_chmod (struct mnt_idmap *idmap , struct dentry *dentry ,
       umode_t mode );

🎀 ARGUMENTS 🎀

• idmap — the idmap of the mount the inode was found from. yes bestie, that exact mount's idmap.
• dentry — the dentry to check permissions on. permission-check main character energy.
• mode — the new mode of the inode. fresh mode, fresh vibe.

🦋 DESCRIPTION 🦋

so here's the tea ☕: if the dentry has been found through an idmapped mount, you absolutely must pass the idmap of the vfsmount through idmap. not optional, bestie.

this function will then take care to map the inode according to idmap before checking permissions. it's giving responsible ✨

on non-idmapped mounts, or if permission checking is to be performed on the raw inode, simply pass nop_mnt_idmap. that's the shortcut, and it's valid here 🫶

lowkey important: pass the right idmap for idmapped mounts, or nop_mnt_idmap for the non-idmapped/raw-inode case. the function handles the mapping before permission checking, periodt.

🌈 SEE ALSO 🌈

• Kernel file ./fs/posix_acl.c
• posix_acl_update_mode(9)
• posix_acl_from_xattr(9)
• vfs_posix_acl_to_xattr(9)
• vfs_set_acl(9)
• vfs_get_acl(9)
• vfs_remove_acl(9)

mwah 💋 this page comes from ./fs and it's dated October 2026 — thanks for coming to my Unix talk, bestie 🎀✨