CVE-2026-43265

Description

In the Linux kernel, the following vulnerability has been resolved: KVM: x86: Ignore -EBUSY when checking nested events from vcpu_block() Ignore -EBUSY when checking nested events after exiting a blocking state while L2 is active, as exiting to userspace will generate a spurious userspace exit, usually with KVM_EXIT_UNKNOWN, and likely lead to the VM's demise. Continuing with the wakeup isn't perfect either, as *something* has gone sideways if a vCPU is awakened in L2 with an injected event (or worse, a nested run pending), but continuing on gives the VM a decent chance of surviving without any major side effects. As explained in the Fixes commits, it _should_ be impossible for a vCPU to be put into a blocking state with an already-injected event (exception, IRQ, or NMI). Unfortunately, userspace can stuff MP_STATE and/or injected events, and thus put the vCPU into what should be an impossible state. Don't bother trying to preserve the WARN, e.g. with an anti-syzkaller Kconfig, as WARNs can (hopefully) be added in paths where _KVM_ would be violating x86 architecture, e.g. by WARNing if KVM attempts to inject an exception or interrupt while the vCPU isn't running.

Affected products

Version statuses are supplied by the assigning organization. Consult the original record for detailed ranges and platform conditions.

References

• https://git.kernel.org/stable/c/78265cd066d73a5cb41c088fcae4a2515e480d97 ↗
• https://git.kernel.org/stable/c/ec3be7dc9391085a2d96700e159d66d1328b7ff6 ↗
• https://git.kernel.org/stable/c/2657439265d34a911886b916ba8be97ecc117d51 ↗
• https://git.kernel.org/stable/c/1e88b5f854bdb469424132e0bb44793ad7a7c20a ↗
• https://git.kernel.org/stable/c/1c957773063ed3264953597e32990a748381caf6 ↗
• https://git.kernel.org/stable/c/ead63640d4e72e6f6d464f4e31f7fecb79af8869 ↗