A flaw was found in the Red Hat Linux kernel. It's possible to send arbitrary signals to a privileged (suidroot) parent process.
Mitigation for this issue is either not available or the currently available options don't meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base or stability.
The "incorrect initialization of the process id" of the flaw is actual only for Red Hat Enterprise Linux (starting from 8.3), and non-actual for other (upstream) Linux distributions.
More details about this:
In fork.c:dup_task_struct(), after task->task_struct_rh allocated by kmalloc_node(), task_struct_rh->self_exec_id and
task_struct_rh->vtime_cpu are not initialized, which upstream do initialize them in arch_dup_task_struct().
Steps to Reproduce:
1. Compile this module
printk(KERN_INFO "[parent ] parent_exec_id: %llu, self_exec_id: %llu\n",
printk(KERN_INFO "[current] parent_exec_id: %llu, self_exec_id: %llu\n",
2. Load it and check dmesg output
[264937.255323] [parent ] parent_exec_id: 64, self_exec_id: 481036337297 <-- seems it is some random value from slab
[264937.255324] [current] parent_exec_id: 481036337297, self_exec_id: 481036337297
[264937.255323] [parent ] parent_exec_id: 64, self_exec_id: 65
[264937.255324] [current] parent_exec_id: 65, self_exec_id: 65
Additional information about the possibility of the integer overflow for the value tsk->parent->self_exec_id:
The incorrect initialization of the process id affects Red Hat Enterprise Linux only.
The description of the flaw:
"A flaw possibility of race condition and incorrect initialization of the process id was found in the Linux kernel child/parent process identification handling while filtering signal handlers. A local attacker is able to abuse this flaw to bypass checks to send any signal to a privileged process."
The patch from the reference is for the "race condition" only:
The other patch for the "incorrect initialization of the process id" is internal and for the Red Hat Enterprise Linux only:
Name: Eddy Wu (trendmicro.com)