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| author | Sean Christopherson <seanjc@google.com> | 2023-02-11 01:07:19 +0000 |
|---|---|---|
| committer | Sean Christopherson <seanjc@google.com> | 2023-05-26 11:23:50 -0700 |
| commit | 76021e96d781e1fe8de02ebe52f3eb276716b6b0 (patch) | |
| tree | 033294715a879c953a770b9ffc12c0fce2f9617d /virt/kvm | |
| parent | b9846a698c9aff4eb2214a06ac83638ad098f33f (diff) | |
| download | lwn-76021e96d781e1fe8de02ebe52f3eb276716b6b0.tar.gz lwn-76021e96d781e1fe8de02ebe52f3eb276716b6b0.zip | |
KVM: Protect vcpu->pid dereference via debugfs with RCU
Wrap the vcpu->pid dereference in the debugfs hook vcpu_get_pid() with
proper RCU read (un)lock. Unlike the code in kvm_vcpu_ioctl(),
vcpu_get_pid() is not a simple access; the pid pointer is passed to
pid_nr() and fully dereferenced if the pointer is non-NULL.
Failure to acquire RCU could result in use-after-free of the old pid if
a different task invokes KVM_RUN and puts the last reference to the old
vcpu->pid between vcpu_get_pid() reading the pointer and dereferencing it
in pid_nr().
Fixes: e36de87d34a7 ("KVM: debugfs: expose pid of vcpu threads")
Link: https://lore.kernel.org/r/20230211010719.982919-1-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
Diffstat (limited to 'virt/kvm')
| -rw-r--r-- | virt/kvm/kvm_main.c | 5 |
1 files changed, 4 insertions, 1 deletions
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c index 479802a892d4..6a658f30af91 100644 --- a/virt/kvm/kvm_main.c +++ b/virt/kvm/kvm_main.c @@ -3870,7 +3870,10 @@ static int create_vcpu_fd(struct kvm_vcpu *vcpu) static int vcpu_get_pid(void *data, u64 *val) { struct kvm_vcpu *vcpu = data; - *val = pid_nr(rcu_access_pointer(vcpu->pid)); + + rcu_read_lock(); + *val = pid_nr(rcu_dereference(vcpu->pid)); + rcu_read_unlock(); return 0; } |