Re: [dpdk-dev] [dpdk-stable] [v1, 2/2] bonding: fix PCI address comparison on non-pci ports

[Ferruh Yigit <ferruh.yigit@intel.com>]

On 12/16/2020 12:14 PM, Min Hu (Connor) wrote:
> Hi,
>      sorry for late reply.
>      I know what you mean. But "find_port_id_by_pci_addr"
> is one static type funtion. it is only used in the function
> "parse_port_id". what you modified in "find_port_id_by_pci_addr"
> is totally done before "find_port_id_by_pci_addr" in the function
> "parse_port_id". That is, it first find pci_bus, then find
> rte_pci_device, at last get port id.
> So the bug you described will not happen in current version,
> unless others directly use the function "find_port_id_by_pci_addr"
> without considering that rte_eth_devices[] may contain non-pci devices.
> 
> So, I think the patch is OK to me.
> 
> Acked-by: Min Hu (Connor) <humin29@huawei.com>
> 

Applied to dpdk-next-net/main, thanks.

> 
> 在 2020/12/7 22:07, Gaëtan Rivet 写道:
>> On 26/11/20 10:24 +0800, Min Hu (Connor) wrote:
>>> what scenarios may cause bugs in old ways.
>>> Could you give an example, thanks.
>>
>> Hello,
>>
>> For example in the following code:
>>
>> -       RTE_ETH_FOREACH_DEV(i) {
>> -               pci_dev = RTE_ETH_DEV_TO_PCI(&rte_eth_devices[i]);
>> -               eth_pci_addr = &pci_dev->addr;
>>
>> All ethdev are iterated, before reading their supposed PCI addresses, and
>> comparing those to the one passed in arguments.
>>
>> But not all ethdev will be PCI devices, so the cast is incorrect. It will do
>> a containerof() on a structure that it supposes contains an rte_device at the
>> offset 16 (two pointers accounting for the TAILQ_ENTRY()), but nothing 
>> prevents any
>> other bus from implementing their device with any other layout.
>>
>> So the cast is wrong, but generally it will give out readable memory at least.
>> Then the field ((eth_dev)->device)->addr will be read and compared against the 
>> input,
>> with arbitrary data here.
>>
>> A scenario that could cause bug would be when another bus implements a device
>> in such a way that it will write plausible binary rep of PCI addresses at the
>> same offset, and match a request from a user. The bonding PMD would take the
>> device over without properly checking that it is actually a PCI device.
>>
>>
>> There have been APIs introduced in the EAL to simplify the iteration of
>> devices, especially restricted to buses. Those APIs should be used instead.
>> The current implementation is inefficient and wrong. It will work in most cases
>> but can still trigger weird issues for users, especially in cases that bonding
>> PMD devs won't generally encounter (with setups where multiple buses are used
>> with a variety of devices).
>>
>> Regards,
>>