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fchownat - change ownership of a file or directory relative to a directory file descriptor.


The fchownat() system call provides a mechanism to modify the ownership (both user and group) of a specified file or directory.

Unlike the chown() system call, fchownat() allows operations relative to a directory referenced by a given file descriptor. This is particularly useful when working within specific directory contexts or when the exact path to a file or directory might not be directly accessible or known.


  • dirfd:int[K] - File descriptor pointing to the directory relative to which the pathname is interpreted.
  • pathname:const char *[U] - The path to the file or directory whose ownership is to be changed.
  • owner:uid_t[K] - The user ID to be set. If set to -1, the user ID isn't changed.
  • group:gid_t[K] - The group ID to be set. If set to -1, the group ID isn't changed.
  • flags:int[K] - Flags to modify function behavior (e.g., AT_SYMLINK_NOFOLLOW to not follow symbolic links).

Available Tags

  • K - Originated from kernel-space.
  • U - Originated from user space.
  • TOCTOU - Vulnerable to TOCTOU (time of check, time of use).
  • OPT - Optional argument - might not always be available (passed with null value).




Tracepoint (through sys_enter).


To observe and record instances when the fchownat() system call is invoked, capturing details about the target file or directory, as well as the new ownership details.

Example Use Case

In environments with strict access controls, monitoring changes in file or directory ownership can be crucial to maintain security and data integrity.


Inappropriate use or vulnerabilities linked to the fchownat() system call can potentially expose files or directories to unauthorized users, posing data integrity and security risks.

  • chown() - Change ownership of a file.
  • lchown() - Change ownership of a symbolic link.
  • fchown() - Change ownership of a file via its file descriptor.

This document was automatically generated by OpenAI and reviewed by a Human.