KVM: s390: Fix IRQ injection with SIGP Stop and Store Status

Overview

In the Linux kernel, the following vulnerability has been resolved:

KVM: s390: Fix IRQ injection with SIGP Stop and Store Status

When __inject_sigp_stop() is called for a Stop and Store Status operation, if the vCPU is running, the interrupt is marked as pending and the status is stored by the thread performing the KVM_RUN IOCTL.

If the vCPU is already stopped, the status is stored immediately.

Storing the status means writing into userspace, which might fault, and __inject_sigp_stop() is called from do_inject_vcpu() which in turn is always called holding a spinlock, which is obviously an issue.

Fix this by returning -EWOULDBLOCK from __inject_sigp_stop(), and adding a bool flag to indicate whether a store status is needed. The callers of do_inject_vcpu() are modified to pass the pointer to the bool flag; whenever a Store Status operation is needed, the callers can now perform it outside the spinlock.

Opportunistically refactor kvm_s390_set_irq_state() to use scoped_guard() and __free().

[ Added Fixes tag while picking -- Claudio ]

Affected

• Linux >= 6cddd432e3da5e25eccbc13844d03c871674a62e < 3bd77c59576b1d447fd56cc689ae9523a334b924
• Linux >= 6cddd432e3da5e25eccbc13844d03c871674a62e < a379ac504fcb8c6fc2aa36203f5489b9581eb2e0
• Linux >= 6cddd432e3da5e25eccbc13844d03c871674a62e < d0e3bf633f0585a0c2c2105ea7723777d764fae5
• Linux >= 6cddd432e3da5e25eccbc13844d03c871674a62e < d343407b728a80b74be3c24b59f15e60289ea527
• Linux 4.0

Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.