admin/linux
1
0
Fork 0
mirror of https://github.com/torvalds/linux.git synced 2025-12-07 20:06:24 +00:00
Code Issues Packages Projects Releases Wiki Activity

KVM: VMX: hyper-v: Prevent impossible NULL pointer dereference in evmcs_load()

Browse Source 
GCC 12.3.0 complains about a potential NULL pointer dereference in
evmcs_load() as hv_get_vp_assist_page() can return NULL. In fact, this
cannot happen because KVM verifies (hv_init_evmcs()) that every CPU has a
valid VP assist page and aborts enabling the feature otherwise. CPU
onlining path is also checked in vmx_hardware_enable().

To make the compiler happy and to future proof the code, add a KVM_BUG_ON()
sentinel. It doesn't seem to be possible (and logical) to observe
evmcs_load() happening without an active vCPU so it is presumed that
kvm_get_running_vcpu() can't return NULL.

No functional change intended.

Reported-by: Mirsad Todorovac <mtodorovac69@gmail.com>
Suggested-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Link: https://lore.kernel.org/r/20240816130124.286226-1-vkuznets@redhat.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
This commit is contained in:
Vitaly Kuznetsov
2024-08-16 15:01:24 +02:00
committed by Sean Christopherson
parent 41ab0d59fa
commit 2ab637df5f
1 changed files with 8 additions and 0 deletions
Download Patch File Download Diff File Expand all files Collapse all files

8
arch/x86/kvm/vmx/vmx_onhyperv.h
View File

@@ -104,6 +104,14 @@ static inline void evmcs_load(u64 phys_addr)
struct hv_vp_assist_page *vp_ap =
hv_get_vp_assist_page(smp_processor_id());
/*
* When enabling eVMCS, KVM verifies that every CPU has a valid hv_vp_assist_page()
* and aborts enabling the feature otherwise. CPU onlining path is also checked in
* vmx_hardware_enable().
*/
if (KVM_BUG_ON(!vp_ap, kvm_get_running_vcpu()->kvm))
return;
if (current_evmcs->hv_enlightenments_control.nested_flush_hypercall)
vp_ap->nested_control.features.directhypercall = 1;
vp_ap->current_nested_vmcs = phys_addr;