OOM while idle, from network

Reproduction:
1. kvm -m 512 -net model=rtl8139 ... (512 MB RAM)
2. GRUB "tests"
3. ifconfig
4. run mauve test suite
5. Let virtual machine sit there, do nothing.

Actual result:
After a while (30 minutes):
Out of memory.
(Red on console)
Stack trace says something about an interrupt from the network card (RTL8139...handleInterrupt()), so I assume that's triggered by some network broadcasts or whatever.

There are several of these Exceptions, all with the same stack.

After a while more:
"Maybe stuck in higher priority: IRQ-11"
(grey on console)
Keeps repeating several times per second, filling the screen.
100% CPU usage.

Expected result:
Just sitting there, it machine does not keep using more and more RAM.
This is clearly a leak.

Compare bug 2854 about the class loader, which accounts for most of the memory usage. In contrast, this bug is about the additional memory usage (and failure to free it) *after* the test suite ran and while the machine is just sitting there idly, yet still using more and more RAM.