semget¶

Intro¶

semget - allows processes to obtain access to semaphore sets

Description¶

semget is used to identify and access an existing semaphore set, or to create a new semaphore set. It is typically used to control access to a shared resource. When using semget to create a new semaphore set, an application must specify the size of the set, along with the read and write permissions. The new semaphore set will remain until removed with semctl or the system is rebooted.

If a process attempts to semget a semaphore set with a key that already exists, the process will be granted access to the semaphore set that already exists provided the permissions matches.

There is an upper limit for the number of semaphore sets that may be created with semget. This limit is determined by the hardware platform and kernel configuration.

Arguments¶

key:key_t - Key of the semaphore set. Used to identify a unique semaphore set and can be created using the ftok function.
nsems:int - The number of semaphores contained in the semaphore set specified by key.
semflg:int[U,K,TOCTOU] - Permissions to access the semaphore set, to perform read and write operations.

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)

Hooks¶

sys_semget¶

Type¶

Kprobes

Purpose¶

To track the use of semget syscalls, to identify any potential race conditions, deadlocks or failed resource allocation.

Example Use Case¶

semget is a useful tool for controlling access to a shared resource amongst multiple processes. For example, a server application may want to control access to a file by having one process obtain the file and then use semget to set up a semaphore set that can be used to coordinate between multiple clients that need to access it.

Issues¶

When using semget to create a new semaphore set, care must be taken to ensure that it has been configured properly and the permissions have been set correctly. Race conditions may occur if the semaphore set is not properly configured. Additionally, Once created, the semget call will return a semaphore set identifier and it is the responsibility of the calling process to manage the semaphore set. If the process exits without freeing up the semaphore set it was responsible for, the semaphore set will remain in the system until the system is rebooted.

semop - to specify the operations to be carried out on the semaphore set
semctl - to control the state of the semaphore set
semtimedop - similar to semop but with an option of timing out

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.