Re: [PATCH] sched/ext: fix cpumask leak in scx_init() error path

[Andrea Righi <arighi@nvidia.com>]

Hi Koba,

On Thu, Apr 09, 2026 at 01:23:12AM +0800, KobaK wrote:
> From: Koba Ko <kobak@nvidia.com>
> 
> In scx_init(), two cpumask allocations are combined with || short-circuit
> evaluation. If the first alloc_cpumask_var (scx_bypass_lb_donee_cpumask)
> succeeds but the second (scx_bypass_lb_resched_cpumask) fails, the first
> cpumask is leaked.
> 
> Split the allocations into separate checks with per-allocation error
> messages and free the first cpumask when the second allocation fails.
> 
> Fixes: 95d1df610cdc7 ("sched_ext: Implement load balancer for bypass mode")
> Signed-off-by: Koba Ko <kobak@nvidia.com>
> ---
>  kernel/sched/ext.c | 11 ++++++++---
>  1 file changed, 8 insertions(+), 3 deletions(-)
> 
> diff --git a/kernel/sched/ext.c b/kernel/sched/ext.c
> index b757b853b42bb..0648088a76f09 100644
> --- a/kernel/sched/ext.c
> +++ b/kernel/sched/ext.c
> @@ -9662,9 +9662,14 @@ static int __init scx_init(void)
>  		return ret;
>  	}
>  
> -	if (!alloc_cpumask_var(&scx_bypass_lb_donee_cpumask, GFP_KERNEL) ||
> -	    !alloc_cpumask_var(&scx_bypass_lb_resched_cpumask, GFP_KERNEL)) {
> -		pr_err("sched_ext: Failed to allocate cpumasks\n");
> +	if (!alloc_cpumask_var(&scx_bypass_lb_donee_cpumask, GFP_KERNEL)) {
> +		pr_err("sched_ext: Failed to allocate donee cpumask\n");
> +		return -ENOMEM;
> +	}
> +
> +	if (!alloc_cpumask_var(&scx_bypass_lb_resched_cpumask, GFP_KERNEL)) {
> +		pr_err("sched_ext: Failed to allocate resched cpumask\n");
> +		free_cpumask_var(scx_bypass_lb_donee_cpumask);

We should probably do a proper teardown of the other stuff as well at some point
(sysfs group, kset, PM notifier, etc.), but this looks good to me.

>  		return -ENOMEM;
>  	}
>  
> -- 
> 2.43.0
> 

Acked-by: Andrea Righi <arighi@nvidia.com>

Thanks,
-Andrea