linux-kernel - Re: [PATCH] pci: endpoint: Add missing NULL check for alloc

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Message-ID: <aRJCMEUdjxh5K2UG@lizhi-Precision-Tower-5810>
Date: Mon, 10 Nov 2025 14:51:12 -0500
From: Frank Li <Frank.li@....com>
To: Haotian Zhang <vulab@...as.ac.cn>
Cc: jdmason@...zu.us, dave.jiang@...el.com, allenbh@...il.com,
	mani@...nel.org, kwilczynski@...nel.org, kishon@...nel.org,
	bhelgaas@...gle.com, ntb@...ts.linux.dev, linux-pci@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] pci: endpoint: Add missing NULL check for
 alloc_workqueue()

On Mon, Nov 10, 2025 at 12:04:46PM +0800, Haotian Zhang wrote:
> The alloc_workqueue() function can return NULL on memory allocation
> failure. Without proper error checking, this leads to a NULL pointer
> dereference when queue_work() is later called with the NULL workqueue
> pointer in epf_ntb_epc_init().
>
> Add a NULL check immediately after alloc_workqueue() and return -ENOMEM
> on failure to prevent the driver from loading with an invalid workqueue
> pointer.
>
> Fixes: e35f56bb0330 ("PCI: endpoint: Support NTB transfer between RC and EP")
> Fixes: 8b821cf76150 ("PCI: endpoint: Add EP function driver to provide NTB functionality")
> Signed-off-by: Haotian Zhang <vulab@...as.ac.cn>
> ---
>  drivers/pci/endpoint/functions/pci-epf-ntb.c  | 4 ++++
>  drivers/pci/endpoint/functions/pci-epf-vntb.c | 4 ++++
>  2 files changed, 8 insertions(+)
>
> diff --git a/drivers/pci/endpoint/functions/pci-epf-ntb.c b/drivers/pci/endpoint/functions/pci-epf-ntb.c
> index e01a98e74d21..b3d96a2e3a8c 100644
> --- a/drivers/pci/endpoint/functions/pci-epf-ntb.c
> +++ b/drivers/pci/endpoint/functions/pci-epf-ntb.c
> @@ -2126,6 +2126,10 @@ static int __init epf_ntb_init(void)
>
>  	kpcintb_workqueue = alloc_workqueue("kpcintb", WQ_MEM_RECLAIM |
>  					    WQ_HIGHPRI, 0);
> +	if (!kpcintb_workqueue) {
> +		pr_err("Failed to allocate kpcintb workqueue\n");
> +		return -ENOMEM;
> +	}

Can we direct use system_highpri_wq?

Frank Li
>  	ret = pci_epf_register_driver(&epf_ntb_driver);
>  	if (ret) {
>  		destroy_workqueue(kpcintb_workqueue);
> diff --git a/drivers/pci/endpoint/functions/pci-epf-vntb.c b/drivers/pci/endpoint/functions/pci-epf-vntb.c
> index 83e9ab10f9c4..79800f1fecc3 100644
> --- a/drivers/pci/endpoint/functions/pci-epf-vntb.c
> +++ b/drivers/pci/endpoint/functions/pci-epf-vntb.c
> @@ -1534,6 +1534,10 @@ static int __init epf_ntb_init(void)
>
>  	kpcintb_workqueue = alloc_workqueue("kpcintb", WQ_MEM_RECLAIM |
>  					    WQ_HIGHPRI, 0);
> +	if (!kpcintb_workqueue) {
> +		pr_err("Failed to allocate kpcintb workqueue\n");
> +		return -ENOMEM;
> +	}
>  	ret = pci_epf_register_driver(&epf_ntb_driver);
>  	if (ret) {
>  		destroy_workqueue(kpcintb_workqueue);
> --
> 2.50.1.windows.1
>