CVE-2024-26603 x86/fpu: Stop relying on userspace for info to fault in xsave buffer
A local attacker can cause a kernel infinite loop and system hang by manipulating user-space FPU state during signal return.
- 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-2024-26603?
CVE-2024-26603 is a medium-severity denial of service vulnerability in Linux kernel, published on 24 Feb 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:
x86/fpu: Stop relying on userspace for info to fault in xsave buffer
Before this change, the expected size of the user space buffer was taken from fx_sw->xstate_size. fx_sw->xstate_size can be changed from user-space, so it is possible construct a sigreturn frame where:
* fx_sw->xstate_size is smaller than the size required by valid bits in fx_sw->xfeatures. * user-space unmaps parts of the sigrame fpu buffer so that not all of the buffer required by xrstor is accessible.
In this case, xrstor tries to restore and accesses the unmapped area which results in a fault. But fault_in_readable succeeds because buf + fx_sw->xstate_size is within the still mapped area, so it goes back and tries xrstor again. It will spin in this loop forever.
Instead, fault in the maximum size which can be touched by XRSTOR (taken from fpstate->user_size).
[ dhansen: tweak subject / changelog ]
Weakness: CWE-835
Which versions are affected by CVE-2024-26603?
It affects 1 product.
Products include Linux kernel.
How do I fix CVE-2024-26603?
Apply the vendor's patch.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2024-26603 being exploited?
There is no known exploitation of CVE-2024-26603 in the wild and no public exploit code.
Other vulnerabilities in Linux kernel
Sources
Also known as BELL-CVE-2024-26603, DEBIAN-CVE-2024-26603, GHSA-fq97-hv4f-crm6, UBUNTU-CVE-2024-26603.