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SubjectRe: [PATCH] soc: renesas: rcar-sysc: fix memory leak in rcar_sysc_pd_init
Ni Navid,

thanks for your patch.

On Wed, Sep 25, 2019 at 04:03:53PM -0500, Navid Emamdoost wrote:
> In rcar_sysc_pd_init when looping over info->areas errors may happen but
> the error handling path does not clean up the intermediate allocated
> memories.
>
> This patch changes the error handling path in major and a little the loop
> itself. Inside the loop if an error happens the current pd will be
> released and then it goes to error handling path where it releases any
> previously allocated domains.
>
> Signed-off-by: Navid Emamdoost <navid.emamdoost@gmail.com>
> ---
> drivers/soc/renesas/rcar-sysc.c | 27 ++++++++++++++++++++++++---
> 1 file changed, 24 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/soc/renesas/rcar-sysc.c b/drivers/soc/renesas/rcar-sysc.c
> index 59b5e6b10272..f9613c1ee0a0 100644
> --- a/drivers/soc/renesas/rcar-sysc.c
> +++ b/drivers/soc/renesas/rcar-sysc.c
> @@ -330,10 +330,10 @@ static int __init rcar_sysc_pd_init(void)
> {
> const struct rcar_sysc_info *info;
> const struct of_device_id *match;
> - struct rcar_pm_domains *domains;
> + struct rcar_pm_domains *domains = NULL;
> struct device_node *np;
> void __iomem *base;
> - unsigned int i;
> + unsigned int i, num_areas = 0;
> int error;

Please preserve reverse xmas tree sorting of local variables.

> np = of_find_matching_node_and_match(NULL, rcar_sysc_matches, &match);
> @@ -382,6 +382,7 @@ static int __init rcar_sysc_pd_init(void)
> pd = kzalloc(sizeof(*pd) + strlen(area->name) + 1, GFP_KERNEL);
> if (!pd) {
> error = -ENOMEM;
> + num_areas = i;
> goto out_put;
> }
>
> @@ -393,8 +394,11 @@ static int __init rcar_sysc_pd_init(void)
> pd->flags = area->flags;
>
> error = rcar_sysc_pd_setup(pd);
> - if (error)
> + if (error) {
> + kfree(pd);
> + num_areas = i;
> goto out_put;
> + }
>
> domains->domains[area->isr_bit] = &pd->genpd;
>
> @@ -406,13 +410,30 @@ static int __init rcar_sysc_pd_init(void)
> if (error) {
> pr_warn("Failed to add PM subdomain %s to parent %u\n",
> area->name, area->parent);
> + kfree(pd);
> + num_areas = i;
> goto out_put;
> }
> }
>
> error = of_genpd_add_provider_onecell(np, &domains->onecell_data);
> + of_node_put(np);
> +
> + return error;
>
> out_put:
> + if (domains) {
> + for (i = 0; i < num_areas; i++) {
> + const struct rcar_sysc_area *area = &info->areas[i];
> +
> + if (!area->name) {
> + /* Skip NULLified area */
> + continue;
> + }
> + kfree(domains->domains[area->isr_bit]);

This cleanup doesn't feel correct to me.

For one I think the allocated memory is at
to_rcar_pd(domains->domains[area->isr_bit]);

And for antoher I wonder if it is also necessary to unwind initialisation done
by rcar_sysc_pd_setup() and pm_genpd_add_subdomain();

I think this leads us to the heart of why such unwinding is not present
and that is, I suspect, that its reasonably complex and in the event of
failure the system is very likely unusable. So leaking a bit of memory,
while unpleasent, doesn't effect the user experience.

> + }
> + kfree(domains);
> + }
> of_node_put(np);
> return error;

I think it would be more in keeping with kernel coding style to add
some extra labels for different error paths. I also think you can
utilise the fact that i is already set to the number of allocated areas.

Something like this (completely untested):

out_free_areas:
while (--i > 0) {
/* Cleanup of 'i' goes here */
}
out_free_domains:
kfree(domains);
out_put:
of_node_put(np);
return error;

> }
> --
> 2.17.1
>

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