AlmaLinux OS 9 must disable virtual system calls.
An XCCDF Rule
Description
System calls are special routines in the Linux kernel, which userspace applications ask to do privileged tasks. Invoking a system call is an expensive operation because the processor must interrupt the currently executing task and switch context to kernel mode, and then switch back to userspace after the system call completes. Virtual system calls map a page into userspace that contains some variables and the implementation of some system calls. This allows the system calls to be executed in userspace to alleviate the context switching expense. Virtual system calls provide an opportunity of attack for a user who has control of the return instruction pointer. Disabling virtual system calls help to prevent return oriented programming (ROP) attacks via buffer overflows and overruns.
- ID
- SV-269306r1050188_rule
- Version
- ALMA-09-025650
- Severity
- Medium
- References
- Updated
Remediation Templates
A Manual Procedure
Document the use of virtual system calls with the ISSO as an operational requirement, or disable them with the following command:
$ grubby --update-kernel=ALL --args="vsyscall=none"
Add or modify the following line in "/etc/default/grub" to ensure the configuration survives kernel updates:
GRUB_CMDLINE_LINUX="vsyscall=none"