Re: [PATCH 1/1] kvm: Clear variables which may not be used

[Li Zhang]

On 12/6/21 12:39 PM, Daniel P. Berrangé wrote:

On Mon, Dec 06, 2021 at 12:27:38PM +0100, Li Zhang wrote:

The variables msi, route in kvm_irqchip_send_msi may be uninitialised
values in some cases. It's necessary to clear them.

You say the patch is going to 'clear them' but....

Ah, sorry for my bad. And this is not correct fix.

Signed-off-by: Li Zhang <lizh...@suse.de>
---
  accel/kvm/kvm-all.c | 5 ++---
  1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/accel/kvm/kvm-all.c b/accel/kvm/kvm-all.c
index eecd8031cf..bd50dc6b80 100644
--- a/accel/kvm/kvm-all.c
+++ b/accel/kvm/kvm-all.c
@@ -1913,10 +1913,8 @@ static KVMMSIRoute *kvm_lookup_msi_route(KVMState *s, 
MSIMessage msg)

int kvm_irqchip_send_msi(KVMState *s, MSIMessage msg)

  {
-    struct kvm_msi msi;
-    KVMMSIRoute *route;
-
      if (kvm_direct_msi_allowed) {
+        struct kvm_msi msi;

...but this is still an uninitialized declaration.

          msi.address_lo = (uint32_t)msg.address;
          msi.address_hi = msg.address >> 32;
          msi.data = le32_to_cpu(msg.data);

I guess the bug you were wanting to fix is that this code only
initializes 5 out of 6 struct fields, before calling the
ioctl.

Yes, you are right.

@@ -1926,6 +1924,7 @@ int kvm_irqchip_send_msi(KVMState *s, MSIMessage msg)
          return kvm_vm_ioctl(s, KVM_SIGNAL_MSI, &msi);
      }

+ KVMMSIRoute *route;

This was initialized correctly before and didn't need moving

      route = kvm_lookup_msi_route(s, msg);
      if (!route) {
          int virq;

Regards,
Daniel