Re: [PATCH 1/2] bus/pci: fix a segfault when call callback

[Thomas Monjalon <thomas@monjalon.net>]

21/05/2022 09:05, Min Hu (Connor):
> From: Huisong Li <lihuisong@huawei.com>
> 
> After the driver probe is executed, the callback in application will
> be called. The callback in application may call some APIs which access the

What is the "callback in application" ?
Do you mean the callback on probing event like RTE_ETH_EVENT_NEW?

> rte_pci_driver::driver by the device::driver pointer to get driver
> information. If the rte_pci_device::device::driver pointer isn't pointed to
> rte_pci_driver::driver in rte_pci_probe_one_driver, a segfault will occur.
> For example, when ethdev driver probe completes, the callback in
> application call rte_eth_dev_info_get which use dev->device->driver->name.
> So rte_pci_device::device::driver should point to rte_pci_driver::driver
> before executing the driver probe.

I understand the need and I approve the move.

> Fixes: c752998b5e2e ("pci: introduce library and driver")
> Cc: stable@dpdk.org
> 
> Signed-off-by: Huisong Li <lihuisong@huawei.com>
> Signed-off-by: Min Hu (Connor) <humin29@huawei.com>
> ---
>  drivers/bus/pci/pci_common.c | 13 +++++++++++--
>  1 file changed, 11 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/bus/pci/pci_common.c b/drivers/bus/pci/pci_common.c
> index 4a3a87f24f..507a654779 100644
> --- a/drivers/bus/pci/pci_common.c
> +++ b/drivers/bus/pci/pci_common.c
> @@ -265,11 +265,22 @@ rte_pci_probe_one_driver(struct rte_pci_driver *dr,
>  			dr->driver.name, dev->id.vendor_id, dev->id.device_id,
>  			loc->domain, loc->bus, loc->devid, loc->function,
>  			dev->device.numa_node);
> +
> +	/*
> +	 * After the driver probe is executed, the callback in application will
> +	 * be called. The callback in application may call some APIs which use
> +	 * dev->device.driver to get some driver information. If the driver
> +	 * pointer isn't pointed to driver->driver here, a segfault will occur.
> +	 */

I would like to make this comment simpler
once I'm sure we share the same understanding.

> +	if (!already_probed)
> +		dev->device.driver = &dr->driver;
> +
>  	/* call the driver probe() function */
>  	ret = dr->probe(dr, dev);
>  	if (already_probed)
>  		return ret; /* no rollback if already succeeded earlier */
>  	if (ret) {
> +		dev->device.driver = NULL;
>  		dev->driver = NULL;
>  		if ((dr->drv_flags & RTE_PCI_DRV_NEED_MAPPING) &&
>  			/* Don't unmap if device is unsupported and
> @@ -282,8 +293,6 @@ rte_pci_probe_one_driver(struct rte_pci_driver *dr,
>  		dev->vfio_req_intr_handle = NULL;
>  		rte_intr_instance_free(dev->intr_handle);
>  		dev->intr_handle = NULL;
> -	} else {
> -		dev->device.driver = &dr->driver;
>  	}
>  
>  	return ret;
>