The Linux kernel contained a vulnerability in the LSM subsystem where the function lsm_set_self_attr() did not hold the cred_guard_mutex lock, unlike proc_pid_attr_write() which does. This mutex is important for SELinux and AppArmor security modules to correctly verify if a process is being ptraced before allowing security attribute transitions. The fix involves holding the cred_guard_mutex in lsm_set_self_attr() to prevent potential race conditions or incorrect security checks.

The vulnerability could have allowed SELinux or AppArmor to incorrectly assess ptrace status of a process, potentially leading to unauthorized security attribute transitions. However, no known exploits in the wild have been reported. The impact is limited to systems using SELinux or AppArmor with ptrace checks in place.

A fix has been implemented in the Linux kernel to hold the cred_guard_mutex in lsm_set_self_attr(), aligning with the existing behavior in proc_pid_attr_write(). Users should apply the official Linux kernel updates that include this fix. Since no patch links or vendor advisories are provided here, users should consult their Linux distribution vendors for updated kernel packages containing this fix.