RE: [PATCH net, 2/2] net: mana: Fix accessing freed irq affinity_hint

[Michael Kelley (LINUX)]

From: LKML haiyangz <lkmlhyz@xxxxxxxxxxxxx> On Behalf Of Haiyang Zhang Sent: Thursday, January 26, 2023 1:05 PM
> 
> After calling irq_set_affinity_and_hint(), the cpumask pointer is
> saved in desc->affinity_hint, and will be used later when reading
> /proc/irq/<num>/affinity_hint. So the cpumask variable needs to be
> allocated per irq, and available until freeing the irq. Otherwise,
> we are accessing freed memory when reading the affinity_hint file.
> 
> To fix the bug, allocate the cpumask per irq, and free it just
> before freeing the irq.

Since the cpumask being passed to irq_set_affinity_and_hint()
always contains exactly one CPU, the code can be considerably
simplified by using the pre-calculated and persistent masks
available as cpumask_of(cpu).  All allocation of cpumasks in this
code goes away, and you can set the affinity_hint to NULL in the
cleanup and remove paths without having to free any masks.

Michael

> 
> Cc: stable@xxxxxxxxxxxxxxx
> Fixes: 71fa6887eeca ("net: mana: Assign interrupts to CPUs based on NUMA nodes")
> Signed-off-by: Haiyang Zhang <haiyangz@xxxxxxxxxxxxx>
> ---
>  .../net/ethernet/microsoft/mana/gdma_main.c   | 40 ++++++++++---------
>  include/net/mana/gdma.h                       |  1 +
>  2 files changed, 23 insertions(+), 18 deletions(-)
> 
> diff --git a/drivers/net/ethernet/microsoft/mana/gdma_main.c
> b/drivers/net/ethernet/microsoft/mana/gdma_main.c
> index 3bae9d4c1f08..37473ae3859c 100644
> --- a/drivers/net/ethernet/microsoft/mana/gdma_main.c
> +++ b/drivers/net/ethernet/microsoft/mana/gdma_main.c
> @@ -1219,7 +1219,6 @@ static int mana_gd_setup_irqs(struct pci_dev *pdev)
>  	struct gdma_irq_context *gic;
>  	unsigned int max_irqs;
>  	u16 *cpus;
> -	cpumask_var_t req_mask;
>  	int nvec, irq;
>  	int err, i = 0, j;
> 
> @@ -1240,25 +1239,26 @@ static int mana_gd_setup_irqs(struct pci_dev *pdev)
>  		goto free_irq_vector;
>  	}
> 
> -	if (!zalloc_cpumask_var(&req_mask, GFP_KERNEL)) {
> -		err = -ENOMEM;
> -		goto free_irq;
> -	}
> -
>  	cpus = kcalloc(nvec, sizeof(*cpus), GFP_KERNEL);
>  	if (!cpus) {
>  		err = -ENOMEM;
> -		goto free_mask;
> +		goto free_gic;
>  	}
>  	for (i = 0; i < nvec; i++)
>  		cpus[i] = cpumask_local_spread(i, gc->numa_node);
> 
>  	for (i = 0; i < nvec; i++) {
> -		cpumask_set_cpu(cpus[i], req_mask);
>  		gic = &gc->irq_contexts[i];
>  		gic->handler = NULL;
>  		gic->arg = NULL;
> 
> +		if (!zalloc_cpumask_var(&gic->cpu_hint, GFP_KERNEL)) {
> +			err = -ENOMEM;
> +			goto free_irq;
> +		}
> +
> +		cpumask_set_cpu(cpus[i], gic->cpu_hint);
> +
>  		if (!i)
>  			snprintf(gic->name, MANA_IRQ_NAME_SZ,
> "mana_hwc@pci:%s",
>  				 pci_name(pdev));
> @@ -1269,17 +1269,18 @@ static int mana_gd_setup_irqs(struct pci_dev *pdev)
>  		irq = pci_irq_vector(pdev, i);
>  		if (irq < 0) {
>  			err = irq;
> -			goto free_mask;
> +			free_cpumask_var(gic->cpu_hint);
> +			goto free_irq;
>  		}
> 
>  		err = request_irq(irq, mana_gd_intr, 0, gic->name, gic);
> -		if (err)
> -			goto free_mask;
> -		irq_set_affinity_and_hint(irq, req_mask);
> -		cpumask_clear(req_mask);
> +		if (err) {
> +			free_cpumask_var(gic->cpu_hint);
> +			goto free_irq;
> +		}
> +
> +		irq_set_affinity_and_hint(irq, gic->cpu_hint);
>  	}
> -	free_cpumask_var(req_mask);
> -	kfree(cpus);
> 
>  	err = mana_gd_alloc_res_map(nvec, &gc->msix_resource);
>  	if (err)
> @@ -1288,20 +1289,22 @@ static int mana_gd_setup_irqs(struct pci_dev *pdev)
>  	gc->max_num_msix = nvec;
>  	gc->num_msix_usable = nvec;
> 
> +	kfree(cpus);
>  	return 0;
> 
> -free_mask:
> -	free_cpumask_var(req_mask);
> -	kfree(cpus);
>  free_irq:
>  	for (j = i - 1; j >= 0; j--) {
>  		irq = pci_irq_vector(pdev, j);
>  		gic = &gc->irq_contexts[j];
> 
>  		irq_update_affinity_hint(irq, NULL);
> +		free_cpumask_var(gic->cpu_hint);
>  		free_irq(irq, gic);
>  	}
> 
> +	kfree(cpus);
> +
> +free_gic:
>  	kfree(gc->irq_contexts);
>  	gc->irq_contexts = NULL;
>  free_irq_vector:
> @@ -1329,6 +1332,7 @@ static void mana_gd_remove_irqs(struct pci_dev *pdev)
> 
>  		/* Need to clear the hint before free_irq */
>  		irq_update_affinity_hint(irq, NULL);
> +		free_cpumask_var(gic->cpu_hint);
>  		free_irq(irq, gic);
>  	}
> 
> diff --git a/include/net/mana/gdma.h b/include/net/mana/gdma.h
> index 56189e4252da..4dcafecbd89e 100644
> --- a/include/net/mana/gdma.h
> +++ b/include/net/mana/gdma.h
> @@ -342,6 +342,7 @@ struct gdma_irq_context {
>  	void (*handler)(void *arg);
>  	void *arg;
>  	char name[MANA_IRQ_NAME_SZ];
> +	cpumask_var_t cpu_hint;
>  };
> 
>  struct gdma_context {
> --
> 2.25.1