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| author | David Matlack <dmatlack@google.com> | 2024-05-03 11:17:32 -0700 |
|---|---|---|
| committer | Sean Christopherson <seanjc@google.com> | 2024-06-18 09:20:01 -0700 |
| commit | a6816314af5749cd88944bfdceb270c627cdf348 (patch) | |
| tree | e082018db936c3d3be6219608524d8a508b1c259 /virt | |
| parent | 438a496b9041402736e164c8ebf1368599903958 (diff) | |
| download | linux-a6816314af5749cd88944bfdceb270c627cdf348.tar.gz linux-a6816314af5749cd88944bfdceb270c627cdf348.tar.bz2 linux-a6816314af5749cd88944bfdceb270c627cdf348.zip | |
KVM: Introduce vcpu->wants_to_run
Introduce vcpu->wants_to_run to indicate when a vCPU is in its core run
loop, i.e. when the vCPU is running the KVM_RUN ioctl and immediate_exit
was not set.
Replace all references to vcpu->run->immediate_exit with
!vcpu->wants_to_run to avoid TOCTOU races with userspace. For example, a
malicious userspace could invoked KVM_RUN with immediate_exit=true and
then after KVM reads it to set wants_to_run=false, flip it to false.
This would result in the vCPU running in KVM_RUN with
wants_to_run=false. This wouldn't cause any real bugs today but is a
dangerous landmine.
Signed-off-by: David Matlack <dmatlack@google.com>
Link: https://lore.kernel.org/r/20240503181734.1467938-2-dmatlack@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
Diffstat (limited to 'virt')
| -rw-r--r-- | virt/kvm/kvm_main.c | 3 |
1 files changed, 3 insertions, 0 deletions
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c index fed80bfbe99b..66bfdfa11805 100644 --- a/virt/kvm/kvm_main.c +++ b/virt/kvm/kvm_main.c @@ -4435,7 +4435,10 @@ static long kvm_vcpu_ioctl(struct file *filp, synchronize_rcu(); put_pid(oldpid); } + vcpu->wants_to_run = !READ_ONCE(vcpu->run->immediate_exit); r = kvm_arch_vcpu_ioctl_run(vcpu); + vcpu->wants_to_run = false; + trace_kvm_userspace_exit(vcpu->run->exit_reason, r); break; } |