Re: [Qemu-devel] net: vmxnet3: memory leakage issue

[P J P <ppandit@redhat.com>]

  Hello Jason,

+-- On Fri, 11 Dec 2015, Jason Wang wrote --+
| I think it's possible for attacker. Better wait for Dmitry's answer for
| this.

  Okay.
 
| > +    /* Verify if device is active */
| > +    if (s->device_active) {
| > +        VMW_CFPRN("Vmxnet3 device is active");
| > +        return;
| > +    }
| 
| What if guest want to activate a paused device?

  There is a 'resume' operation defined below.
 
| >      case VMXNET3_CMD_QUIESCE_DEV:
| > -        VMW_CBPRN("Set: VMXNET3_CMD_QUIESCE_DEV - pause the device");
| > -        vmxnet3_deactivate_device(s);
| > +        if (s->device_active & VMXNET3_DEV_ACTIVE) {
| > +            VMW_CBPRN("Set: VMXNET3_CMD_QUIESCE_DEV - pause the device");
| > +            vmxnet3_pause_device(s);
| > +        } else if (s->device_active & VMXNET3_DEV_PAUSE) {
| > +            VMW_CBPRN("Set: VMXNET3_CMD_QUIESCE_DEV - resume the device");
| > +            vmxnet3_resume_device(s);
| > +        }
| 
| Not sure this is the correct behavior. Is there a link to the spec?

  I couldn't find a spec for vmxnet3; I referred the vmxnet3 kernel driver, 
which seems to implement suspend & resume functions.

  -> https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/tree/drivers/net/vmxnet3/vmxnet3_drv.c

In general, Ethernet documents talk about 'pause' frame mechanism to stop NIC 
from buffering more data, till it has space available to process more, when it 
resumes its operation.

Thank you.
--
Prasad J Pandit / Red Hat Product Security Team
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