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authorSean Christopherson <seanjc@google.com>2024-01-10 04:15:33 +0300
committerSean Christopherson <seanjc@google.com>2024-02-06 22:04:58 +0300
commitc2744ed2230a92636f04cde48f2f7d8d3486e194 (patch)
tree92470a1cbed15e087f6dc915e8238519926295a9 /virt
parent8284765f03b7a0b18968cefeb5e78aca647b8f8b (diff)
downloadlinux-c2744ed2230a92636f04cde48f2f7d8d3486e194.tar.xz
KVM: Nullify async #PF worker's "apf" pointer as soon as it might be freed
Nullify the async #PF worker's local "apf" pointer immediately after the point where the structure can be freed by the vCPU. The existing comment is helpful, but easy to overlook as there is no associated code. Update the comment to clarify that it can be freed by as soon as the lock is dropped, as "after this point" isn't strictly accurate, nor does it help understand what prevents the structure from being freed earlier. Reviewed-by: Xu Yilun <yilun.xu@intel.com> Reviewed-by: Vitaly Kuznetsov <vkuznets@redhat.com> Link: https://lore.kernel.org/r/20240110011533.503302-5-seanjc@google.com Signed-off-by: Sean Christopherson <seanjc@google.com>
Diffstat (limited to 'virt')
-rw-r--r--virt/kvm/async_pf.c11
1 files changed, 6 insertions, 5 deletions
diff --git a/virt/kvm/async_pf.c b/virt/kvm/async_pf.c
index 628f6df7609f..99a63bad0306 100644
--- a/virt/kvm/async_pf.c
+++ b/virt/kvm/async_pf.c
@@ -83,13 +83,14 @@ static void async_pf_execute(struct work_struct *work)
apf->vcpu = NULL;
spin_unlock(&vcpu->async_pf.lock);
- if (!IS_ENABLED(CONFIG_KVM_ASYNC_PF_SYNC) && first)
- kvm_arch_async_page_present_queued(vcpu);
-
/*
- * apf may be freed by kvm_check_async_pf_completion() after
- * this point
+ * The apf struct may be freed by kvm_check_async_pf_completion() as
+ * soon as the lock is dropped. Nullify it to prevent improper usage.
*/
+ apf = NULL;
+
+ if (!IS_ENABLED(CONFIG_KVM_ASYNC_PF_SYNC) && first)
+ kvm_arch_async_page_present_queued(vcpu);
trace_kvm_async_pf_completed(addr, cr2_or_gpa);