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

["Min Hu (Connor)" <humin29@huawei.com>]

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>


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,
>