[v1,1/2] ACPI: NFIT: Fix memory leak, and local use of devm_*()

devm_*() family of functions purpose is managing memory attached to a
device. So in general it should only be used for allocations that should
last for the whole lifecycle of the device. This is not the case for
acpi_nfit_init_interleave_set(). There are two allocations that are only
used locally in this function. What's more - if the function exits on
error path memory is never freed. It's still attached to dev and would
be freed on device detach, so this leak could be called a 'local leak'.

Fix this by switching from devm_kcalloc() to kcalloc(), and adding
proper rollback.

Fixes: eaf961536e16 ("libnvdimm, nfit: add interleave-set state-tracking infrastructure")
Reported-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Signed-off-by: Michal Wilczynski <michal.wilczynski@intel.com>
---
 drivers/acpi/nfit/core.c | 23 +++++++++++++++--------
 1 file changed, 15 insertions(+), 8 deletions(-)

On 9/26/23 11:45, Michal Wilczynski wrote:
> devm_*() family of functions purpose is managing memory attached to a
> device. So in general it should only be used for allocations that should
> last for the whole lifecycle of the device. This is not the case for
> acpi_nfit_init_interleave_set(). There are two allocations that are only
> used locally in this function. What's more - if the function exits on
> error path memory is never freed. It's still attached to dev and would
> be freed on device detach, so this leak could be called a 'local leak'.
> 
> Fix this by switching from devm_kcalloc() to kcalloc(), and adding
> proper rollback.
> 
> Fixes: eaf961536e16 ("libnvdimm, nfit: add interleave-set state-tracking infrastructure")
> Reported-by: Andy Shevchenko <andy.shevchenko@gmail.com>
> Signed-off-by: Michal Wilczynski <michal.wilczynski@intel.com>

Reviewed-by: Dave Jiang <dave.jiang@intel.com>
> ---
>  drivers/acpi/nfit/core.c | 23 +++++++++++++++--------
>  1 file changed, 15 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/acpi/nfit/core.c b/drivers/acpi/nfit/core.c
> index f0e6738ae3c9..78f0f855c4de 100644
> --- a/drivers/acpi/nfit/core.c
> +++ b/drivers/acpi/nfit/core.c
> @@ -2262,6 +2262,7 @@ static int acpi_nfit_init_interleave_set(struct acpi_nfit_desc *acpi_desc,
>  	u16 nr = ndr_desc->num_mappings;
>  	struct nfit_set_info2 *info2;
>  	struct nfit_set_info *info;
> +	int err = 0;
>  	int i;
>  
>  	nd_set = devm_kzalloc(dev, sizeof(*nd_set), GFP_KERNEL);
> @@ -2269,13 +2270,15 @@ static int acpi_nfit_init_interleave_set(struct acpi_nfit_desc *acpi_desc,
>  		return -ENOMEM;
>  	import_guid(&nd_set->type_guid, spa->range_guid);
>  
> -	info = devm_kcalloc(dev, nr, sizeof(*info), GFP_KERNEL);
> +	info = kcalloc(nr, sizeof(*info), GFP_KERNEL);
>  	if (!info)
>  		return -ENOMEM;
>  
> -	info2 = devm_kcalloc(dev, nr, sizeof(*info2), GFP_KERNEL);
> -	if (!info2)
> -		return -ENOMEM;
> +	info2 = kcalloc(nr, sizeof(*info2), GFP_KERNEL);
> +	if (!info2) {
> +		err = -ENOMEM;
> +		goto free_info;
> +	}
>  
>  	for (i = 0; i < nr; i++) {
>  		struct nd_mapping_desc *mapping = &ndr_desc->mapping[i];
> @@ -2289,7 +2292,8 @@ static int acpi_nfit_init_interleave_set(struct acpi_nfit_desc *acpi_desc,
>  
>  		if (!memdev || !nfit_mem->dcr) {
>  			dev_err(dev, "%s: failed to find DCR\n", __func__);
> -			return -ENODEV;
> +			err = -ENODEV;
> +			goto free_info2;
>  		}
>  
>  		map->region_offset = memdev->region_offset;
> @@ -2337,10 +2341,13 @@ static int acpi_nfit_init_interleave_set(struct acpi_nfit_desc *acpi_desc,
>  	}
>  
>  	ndr_desc->nd_set = nd_set;
> -	devm_kfree(dev, info);
> -	devm_kfree(dev, info2);
>  
> -	return 0;
> +free_info2:
> +	kfree(info2);
> +free_info:
> +	kfree(info);
> +
> +	return err;
>  }
>  
>  static int ars_get_cap(struct acpi_nfit_desc *acpi_desc,

On Tue, Sep 26, 2023 at 09:45:19PM +0300, Michal Wilczynski wrote:
> devm_*() family of functions purpose is managing memory attached to a
> device. So in general it should only be used for allocations that should
> last for the whole lifecycle of the device. This is not the case for
> acpi_nfit_init_interleave_set(). There are two allocations that are only
> used locally in this function. What's more - if the function exits on
> error path memory is never freed. It's still attached to dev and would
> be freed on device detach, so this leak could be called a 'local leak'.
> 
> Fix this by switching from devm_kcalloc() to kcalloc(), and adding
> proper rollback.

LGTM,
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>

Michal Wilczynski wrote:
> devm_*() family of functions purpose is managing memory attached to a
> device. So in general it should only be used for allocations that should
> last for the whole lifecycle of the device. This is not the case for
> acpi_nfit_init_interleave_set(). There are two allocations that are only
> used locally in this function. What's more - if the function exits on
> error path memory is never freed. It's still attached to dev and would
> be freed on device detach, so this leak could be called a 'local leak'.

This analysis is incorrect devm cleans up on driver ->probe() failure in
addition to ->remove(), and these error returns result in ->probe()
failures. No leak, i.e. this is not a fix.

The conversion to modern probe is ok if you want to resubmit that one
without this intervening change.