close¶

Intro¶

close - Closes a file descriptor.

Description¶

The close() system call closes a file descriptor, so that it no longer refers to any file and may be reused. Any file descriptor that is closed is automatically removed from the range of descriptors checked forready-ness in select() or poll(). The resources associated with a file descriptor are released when all file descriptors reference the same file or pipe are closed.

close also performs a form of synchronization. When all of the file descriptors associated with a pipe have been closed, any process that had the pipe open can detect the termination of the other end of the pipe, and the process can unblock if it was blocked on a read operation.

It is important to close all file descriptors when they are no longer needed, rather than rely on the kernel to do it. Some implementations of select() and poll() attach a copy of the file descriptor table of the process to the kernel data structure associated with the call, for use during the call. If the process has a large file descriptor table and has made a select() or poll() system call, closing a file descriptor could result in the kernel consuming a lot of memory.

Arguments¶

fd:int[K,U] - A file descriptor indicating the open file to close.

Available Tags¶

K - Originated from kernel-space.
U - Originated from user space (for example, pointer to user space memory used to get it)
TOCTOU - Vulnerable to TOCTOU (time of check, time of use)
OPT - Optional argument - might not always be available (passed with null value)

Hooks¶

sys_close¶

Type¶

kprobe + kretprobe

Purpose¶

Allow the tracing of successful close system calls to a file descriptor.

Example Use Case¶

close() can be used to end the use of a file descriptor during the opening of a file descriptor. It can also be used to close resources that are automatically released, such as network sockets.

Issues¶

It is important to note that close() only works on file descriptors, and does not work on file objects as different platforms have different methods for handling file objects.

open, read, write, fsync

This document was automatically generated by OpenAI and needs review. It might not be accurate and might contain errors. The authors of Tracee recommend that the user reads the "events.go" source file to understand the events and their arguments better.