A DMA reentrancy issue was found in the Tulip device emulation in QEMU. When Tulip reads or writes to the rx/tx descriptor or copies the rx/tx frame, it doesnt check whether the destination address is its own MMIO address. This can cause the device to trigger MMIO handlers multiple times, possibly leading to a stack or heap overflow. A malicious guest could use this flaw to crash the QEMU process on the host, resulting in a denial of service condition.
The product does not properly control the allocation and maintenance of a limited resource.
| Name | Vendor | Start Version | End Version |
|---|---|---|---|
| Qemu | Qemu | 4.2.0 (including) | 7.1.0 (including) |
| Qemu | Ubuntu | devel | * |
| Qemu | Ubuntu | kinetic | * |
| Qemu | Ubuntu | trusty | * |
| Qemu | Ubuntu | xenial | * |
Mitigation of resource exhaustion attacks requires that the target system either:
The first of these solutions is an issue in itself though, since it may allow attackers to prevent the use of the system by a particular valid user. If the attacker impersonates the valid user, they may be able to prevent the user from accessing the server in question.
The second solution is simply difficult to effectively institute – and even when properly done, it does not provide a full solution. It simply makes the attack require more resources on the part of the attacker.