Subject: Re: [PATCH] ice: Fix improper handling of refcount in ice_sriov_set_msix_vec_count()

From: Simon Horman <[email-masked]>
Date: Sat, 10 Aug 2024 10:10:15 +0100

On Fri, Aug 09, 2024 at 12:59:11PM +0800, Gui-Dong Han wrote:
> This patch addresses an issue with improper reference count handling in the
> ice_sriov_set_msix_vec_count() function. Specifically, the function calls
> ice_get_vf_by_id(), which increments the reference count of the vf pointer.
> If the subsequent call to ice_get_vf_vsi() fails, the function currently
> returns an error without decrementing the reference count of the vf
> pointer, leading to a reference count leak.
> 
> The correct behavior, as implemented in this patch, is to decrement the
> reference count using ice_put_vf(vf) before returning an error when vsi
> is NULL.
>  
> This bug was identified by an experimental static analysis tool developed
> by our team. The tool specializes in analyzing reference count operations
> and identifying potential mismanagement of reference counts. In this case,
> the tool flagged the missing decrement operation as a potential issue,
> leading to this patch.
> 
> Fixes: 4035c72dc1ba ("ice: reconfig host after changing MSI-X on VF")
> Cc: [email-masked]
> Signed-off-by: Gui-Dong Han <[email-masked]>

Thanks Gui-Dong Han,

I agree with your analysis.
However, I wonder if the same resource leak can occur
in the unroll label, if the if clause results in a return.

It is around line 1444 without your patch applied.

	vf->first_vector_idx = ice_sriov_get_irqs(pf, vf->num_msix);
	if (vf->first_vector_idx < 0)
		return -EINVAL;

> ---
>  drivers/net/ethernet/intel/ice/ice_sriov.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/net/ethernet/intel/ice/ice_sriov.c b/drivers/net/ethernet/intel/ice/ice_sriov.c
> index 55ef33208456..eb5030aba9a5 100644
> --- a/drivers/net/ethernet/intel/ice/ice_sriov.c
> +++ b/drivers/net/ethernet/intel/ice/ice_sriov.c
> @@ -1096,8 +1096,10 @@ int ice_sriov_set_msix_vec_count(struct pci_dev *vf_dev, int msix_vec_count)
>  		return -ENOENT;
>  
>  	vsi = ice_get_vf_vsi(vf);
> -	if (!vsi)
> +	if (!vsi) {
> +		ice_put_vf(vf);
>  		return -ENOENT;
> +	}
>  
>  	prev_msix = vf->num_msix;
>  	prev_queues = vf->num_vf_qs;
> -- 
> 2.25.1
> 
>