Subject: Re: [PATCH v2 7/9] vdpa: solidrun: Fix potential UB bug with devres

From: "Michael S. Tsirkin" <[email-masked]>
Date: Wed, 21 Aug 2024 08:12:50 -0400

On Wed, Aug 21, 2024 at 09:18:40AM +0200, Philipp Stanner wrote:
> In psnet_open_pf_bar() a string later passed to pcim_iomap_regions() is
> placed on the stack. Neither pcim_iomap_regions() nor the functions it
> calls copy that string.
> 
> Should the string later ever be used, this, consequently, causes
> undefined behavior since the stack frame will by then have disappeared.
> 
> Fix the bug by allocating the string on the heap through
> devm_kasprintf().
> 
> Cc: [email-masked]	# v6.3
> Fixes: 51a8f9d7f587 ("virtio: vdpa: new SolidNET DPU driver.")
> Reported-by: Christophe JAILLET <[email-masked]>
> Closes: https://lore.kernel.org/all/[email-masked]/
> Suggested-by: Andy Shevchenko <[email-masked]>
> Signed-off-by: Philipp Stanner <[email-masked]>

I don't get why is this a part of a cleanup series -
looks like an unrelated bugfix?

> ---
>  drivers/vdpa/solidrun/snet_main.c | 7 +++++--
>  1 file changed, 5 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/vdpa/solidrun/snet_main.c b/drivers/vdpa/solidrun/snet_main.c
> index 99428a04068d..4d42a05d70fc 100644
> --- a/drivers/vdpa/solidrun/snet_main.c
> +++ b/drivers/vdpa/solidrun/snet_main.c
> @@ -555,7 +555,7 @@ static const struct vdpa_config_ops snet_config_ops = {
>  
>  static int psnet_open_pf_bar(struct pci_dev *pdev, struct psnet *psnet)
>  {
> -	char name[50];
> +	char *name;
>  	int ret, i, mask = 0;
>  	/* We don't know which BAR will be used to communicate..
>  	 * We will map every bar with len > 0.
> @@ -573,7 +573,10 @@ static int psnet_open_pf_bar(struct pci_dev *pdev, struct psnet *psnet)
>  		return -ENODEV;
>  	}
>  
> -	snprintf(name, sizeof(name), "psnet[%s]-bars", pci_name(pdev));
> +	name = devm_kasprintf(&pdev->dev, GFP_KERNEL, "psnet[%s]-bars", pci_name(pdev));
> +	if (!name)
> +		return -ENOMEM;
> +
>  	ret = pcim_iomap_regions(pdev, mask, name);
>  	if (ret) {
>  		SNET_ERR(pdev, "Failed to request and map PCI BARs\n");
> -- 
> 2.46.0