CVE-2023-52597 KVM: s390: fix setting of fpc register
A race condition in KVM s390 allows host process corruption, potentially enabling privilege escalation or code execution on the host.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2023-52597?
CVE-2023-52597 is a medium-severity vulnerability in Debian Debian Linux, published on 6 Mar 2024. 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:
KVM: s390: fix setting of fpc register
kvm_arch_vcpu_ioctl_set_fpu() allows to set the floating point control (fpc) register of a guest cpu. The new value is tested for validity by temporarily loading it into the fpc register.
This may lead to corruption of the fpc register of the host process: if an interrupt happens while the value is temporarily loaded into the fpc register, and within interrupt context floating point or vector registers are used, the current fp/vx registers are saved with save_fpu_regs() assuming they belong to user space and will be loaded into fp/vx registers when returning to user space.
test_fp_ctl() restores the original user space / host process fpc register value, however it will be discarded, when returning to user space.
In result the host process will incorrectly continue to run with the value that was supposed to be used for a guest cpu.
Fix this by simply removing the test. There is another test right before the SIE context is entered which will handles invalid values.
This results in a change of behaviour: invalid values will now be accepted instead of that the ioctl fails with -EINVAL. This seems to be acceptable, given that this interface is most likely not used anymore, and this is in addition the same behaviour implemented with the memory mapped interface (replace invalid values with zero) - see sync_regs() in kvm-s390.c.
Which versions are affected by CVE-2023-52597?
It affects 2 products.
Products include Debian Debian Linux, Linux kernel.
How do I fix CVE-2023-52597?
Apply the vendor's patch.
Is CVE-2023-52597 being exploited?
There is no known exploitation of CVE-2023-52597 in the wild and no public exploit code.
Other vulnerabilities in Debian Debian Linux
Sources
Also known as BELL-CVE-2023-52597, DEBIAN-CVE-2023-52597, GHSA-6j3q-64jm-q33g, UBUNTU-CVE-2023-52597.