CVE-2022-49164 powerpc/tm: Fix more userspace r13 corruption
A race condition in the Linux kernel's PowerPC transactional memory handling can corrupt user registers, potentially allowing privilege escalation or code execution.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2022-49164?
CVE-2022-49164 is a medium-severity memory corruption vulnerability in Linux kernel, published on 26 Feb 2025. It can only be exploited from the same machine or local network, with no action from the victim.
Official description
In the Linux kernel, the following vulnerability has been resolved:
powerpc/tm: Fix more userspace r13 corruption
Commit cf13435b730a ("powerpc/tm: Fix userspace r13 corruption") fixes a problem in treclaim where a SLB miss can occur on the thread_struct->ckpt_regs while SCRATCH0 is live with the saved user r13 value, clobbering it with the kernel r13 and ultimately resulting in kernel r13 being stored in ckpt_regs.
There is an equivalent problem in trechkpt where the user r13 value is loaded into r13 from chkpt_regs to be recheckpointed, but a SLB miss could occur on ckpt_regs accesses after that, which will result in r13 being clobbered with a kernel value and that will get recheckpointed and then restored to user registers.
The same memory page is accessed right before this critical window where a SLB miss could cause corruption, so hitting the bug requires the SLB entry be removed within a small window of instructions, which is possible if a SLB related MCE hits there. PAPR also permits the hypervisor to discard this SLB entry (because slb_shadow->persistent is only set to SLB_NUM_BOLTED) although it's not known whether any implementations would do this (KVM does not). So this is an extremely unlikely bug, only found by inspection.
Fix this by also storing user r13 in a temporary location on the kernel stack and don't change the r13 register from kernel r13 until the RI=0 critical section that does not fault.
The SCRATCH0 change is not strictly part of the fix, it's only used in the RI=0 section so it does not have the same problem as the previous SCRATCH0 bug.
Which versions are affected by CVE-2022-49164?
It affects 1 product.
Products include Linux kernel.
How do I fix CVE-2022-49164?
Apply the vendor's patch.
Upgrade to the fixed version. Memory-safe languages, compiler hardening and fuzzing prevent most new cases. More about Memory corruption.
Is CVE-2022-49164 being exploited?
There is no known exploitation of CVE-2022-49164 in the wild and no public exploit code.
Other vulnerabilities in Linux kernel
Sources
Also known as DEBIAN-CVE-2022-49164, GHSA-r9xv-hg83-5rcx, ROOT-OS-DEBIAN-11-CVE-2022-49164, UBUNTU-CVE-2022-49164.