afs_syscall - Handler for the
sys_afs system call.
afs_syscall is a handler for the
sys_afs system call, which is used to process AFS requests. The requests are contributed by kernel modules with the help of an ioctl to the AFS device driver. Requests include operations such as file read/write, access control and other complex operations.
afs_syscall allows AFS requests to be processed by the system in a secure and consistent way. Additionally, requests can be safely and easily marshalled between user and kernel space.
However, performance can be an issue as there is some overhead in the marshalling process. Since operations can take a long time to complete, potential race conditions or other security issues can occur if care is not taken.
cmd:unsigned int[K] - Type of command being requested.
pn:struct pt_regs*[K, U] - Pointer to task's registers.
arg4:unsigned long[K,U] - Arguments to the command.
- 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)
Kprobe + Kretprobe
The do_sys_afs function is hooked in order to instrument the syscall handlers. This informs the tracing system whenever a syscall is executed, so the tracing system can collect information about the syscall.
Example Use Case¶
For example, the AFS tracing system could be set up with
afs_syscall so that whenever an AFS request is made, the arguments, timestamps and other relevant information can be collected. This information can be used to analyse system behaviour and observe the impact of AFS requests.
afs_syscall requires that the arguments to the request are correctly marshalled between user and kernel space. If the arguments are malformed or invalid, it could potentially lead to a system crash or other unpredictable behaviour.
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.