Re: [net,v2,02/12] idpf: skip deallocating bufq_sets from rx_qgrp if it is NULL

[Jakub Kicinski <kuba@kernel.org>]

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---
idpf: skip deallocating bufq_sets from rx_qgrp if it is NULL

This patch adds a NULL check for rx_qgrp->splitq.bufq_sets to prevent
kernel panic when idpf_rxq_group_alloc() fails during initialization and
the error path calls idpf_rxq_sw_queue_rel(). The panic was occurring
during device opening when adding to a bonding interface.

> diff --git a/drivers/net/ethernet/intel/idpf/idpf_txrx.c b/drivers/net/ethernet/intel/idpf/idpf_txrx.c
> index 761a77510467..59aafadae3d0 100644
> --- a/drivers/net/ethernet/intel/idpf/idpf_txrx.c
> +++ b/drivers/net/ethernet/intel/idpf/idpf_txrx.c
> @@ -1341,6 +1341,9 @@ static void idpf_txq_group_rel(struct idpf_q_vec_rsrc *rsrc)
>   */
>  static void idpf_rxq_sw_queue_rel(struct idpf_rxq_group *rx_qgrp)
>  {
> +	if (!rx_qgrp->splitq.bufq_sets)
> +		return;
> +
>  	for (unsigned int i = 0; i < rx_qgrp->splitq.num_bufq_sets; i++) {
>  		struct idpf_bufq_set *bufq_set = &rx_qgrp->splitq.bufq_sets[i];
>
>  		for (unsigned int j = 0; j < bufq_set->num_refillqs; j++) {
>  			kfree(bufq_set->refillqs[j].ring);
>  			bufq_set->refillqs[j].ring = NULL;
                           ^^^^^^
This patch adds a NULL check for bufq_sets, but does the same issue
exist for refillqs?

Looking at idpf_rxq_group_alloc() in the same file, it first sets
bufq_set->num_refillqs to a non-zero value, then attempts to allocate
refillqs:

idpf_rxq_group_alloc() {
    ...
    bufq_set->num_refillqs = num_rxq;
    bufq_set->refillqs = kcalloc(bufq_set->num_refillqs,
                                  sizeof(struct idpf_sw_queue),
                                  GFP_KERNEL);
    if (!bufq_set->refillqs) {
        err = -ENOMEM;
        goto err_alloc;
    }
    ...
}

If this allocation fails, bufq_set->refillqs is NULL but
bufq_set->num_refillqs is non-zero. The error path calls
idpf_rxq_sw_queue_rel() which now passes the bufq_sets check but then
dereferences bufq_set->refillqs[j].ring in the inner loop.

The inner loop condition (j < bufq_set->num_refillqs) would be true,
causing the same NULL pointer dereference the patch is meant to prevent.

Would this need a similar check before the inner loop, similar to the
bufq_sets check added in this patch?