[BUG] arch/x86/kvm/vmx/vmx_onhyperv.h:109:36: error: dereference of NULL ‘0’

[Mirsad Todorovac <mtodorovac69@gmail.com>]

Hi, all!

Here is another potential NULL pointer dereference in kvm subsystem of linux stable vanilla 6.10,
as GCC 12.3.0 complains.

(Please don't throw stuff at me, I think this is the last one for today :-)

arch/x86/include/asm/mshyperv.h
-------------------------------
  242 static inline struct hv_vp_assist_page *hv_get_vp_assist_page(unsigned int cpu)
  243 {
  244         if (!hv_vp_assist_page)
  245                 return NULL;
  246 
  247         return hv_vp_assist_page[cpu];
  248 }

arch/x86/kvm/vmx/vmx_onhyperv.h
-------------------------------
  102 static inline void evmcs_load(u64 phys_addr)
  103 {
  104         struct hv_vp_assist_page *vp_ap =
  105                 hv_get_vp_assist_page(smp_processor_id());
  106 
  107         if (current_evmcs->hv_enlightenments_control.nested_flush_hypercall)
  108                 vp_ap->nested_control.features.directhypercall = 1;
  109         vp_ap->current_nested_vmcs = phys_addr;
  110         vp_ap->enlighten_vmentry = 1;
  111 }

Now, this one is simple: hv_vp_assist_page(cpu) can return NULL, and in line 104 it is assigned
to wp_ap, which is dereferenced in lines 108, 109, and 110, which is not checked against returning
NULL by hv_vp_assist_page().

Commits 50a82b0eb88c1 and a46d15cc1ae5a are related to the issue.

Hope this helps.

Best regards,
Mirsad Todorovac