cgroup/cpuset: Free sched domains on rebuild guard failure

[PATCH] cgroup/cpuset: Free sched domains on rebuild guard failure

Posted by Guopeng Zhang 1 week, 4 days ago

From: Guopeng Zhang <zhangguopeng@kylinos.cn>

generate_sched_domains() returns sched-domain masks and optional
attributes that are normally handed to partition_sched_domains(), which
takes ownership of them.

rebuild_sched_domains_locked() has a WARN guard after
generate_sched_domains() and before partition_sched_domains() to avoid
passing offline CPUs into the scheduler domain rebuild path. If that
guard fires, the function currently returns directly without freeing
the generated doms and attr.

Free the generated sched-domain masks and attributes before returning
from the guard failure path.

Signed-off-by: Guopeng Zhang <zhangguopeng@kylinos.cn>
---
 kernel/cgroup/cpuset.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c
index 51327333980a..c5fdebc205d8 100644
--- a/kernel/cgroup/cpuset.c
+++ b/kernel/cgroup/cpuset.c
@@ -1004,8 +1004,11 @@ void rebuild_sched_domains_locked(void)
 	* prevent the panic.
 	*/
 	for (i = 0; doms && i < ndoms; i++) {
-		if (WARN_ON_ONCE(!cpumask_subset(doms[i], cpu_active_mask)))
+		if (WARN_ON_ONCE(!cpumask_subset(doms[i], cpu_active_mask))) {
+			free_sched_domains(doms, ndoms);
+			kfree(attr);
 			return;
+		}
 	}
 
 	/* Have scheduler rebuild the domains */
-- 
2.43.0

Re: [PATCH] cgroup/cpuset: Free sched domains on rebuild guard failure

Posted by Ridong Chen 6 days, 5 hours ago


On 2026/5/28 17:37, Guopeng Zhang wrote:
> From: Guopeng Zhang <zhangguopeng@kylinos.cn>
> 
> generate_sched_domains() returns sched-domain masks and optional
> attributes that are normally handed to partition_sched_domains(), which
> takes ownership of them.
> 
> rebuild_sched_domains_locked() has a WARN guard after
> generate_sched_domains() and before partition_sched_domains() to avoid
> passing offline CPUs into the scheduler domain rebuild path. If that
> guard fires, the function currently returns directly without freeing
> the generated doms and attr.
> 
> Free the generated sched-domain masks and attributes before returning
> from the guard failure path.
> 
> Signed-off-by: Guopeng Zhang <zhangguopeng@kylinos.cn>
> ---
>  kernel/cgroup/cpuset.c | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c
> index 51327333980a..c5fdebc205d8 100644
> --- a/kernel/cgroup/cpuset.c
> +++ b/kernel/cgroup/cpuset.c
> @@ -1004,8 +1004,11 @@ void rebuild_sched_domains_locked(void)
>  	* prevent the panic.
>  	*/
>  	for (i = 0; doms && i < ndoms; i++) {
> -		if (WARN_ON_ONCE(!cpumask_subset(doms[i], cpu_active_mask)))
> +		if (WARN_ON_ONCE(!cpumask_subset(doms[i], cpu_active_mask))) {
> +			free_sched_domains(doms, ndoms);
> +			kfree(attr);
>  			return;
> +		}
>  	}
>  
>  	/* Have scheduler rebuild the domains */

Thank you. This helps prevent a memory leak in this abnormal scenario. I
should have included it when I originally added this check.

-- 
Best regards,
Ridong

Re: [PATCH] cgroup/cpuset: Free sched domains on rebuild guard failure

Posted by Waiman Long 1 week, 2 days ago

On 5/28/26 5:37 AM, Guopeng Zhang wrote:
> From: Guopeng Zhang <zhangguopeng@kylinos.cn>
>
> generate_sched_domains() returns sched-domain masks and optional
> attributes that are normally handed to partition_sched_domains(), which
> takes ownership of them.
>
> rebuild_sched_domains_locked() has a WARN guard after
> generate_sched_domains() and before partition_sched_domains() to avoid
> passing offline CPUs into the scheduler domain rebuild path. If that
> guard fires, the function currently returns directly without freeing
> the generated doms and attr.
>
> Free the generated sched-domain masks and attributes before returning
> from the guard failure path.
>
> Signed-off-by: Guopeng Zhang <zhangguopeng@kylinos.cn>
> ---
>   kernel/cgroup/cpuset.c | 5 ++++-
>   1 file changed, 4 insertions(+), 1 deletion(-)
>
> diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c
> index 51327333980a..c5fdebc205d8 100644
> --- a/kernel/cgroup/cpuset.c
> +++ b/kernel/cgroup/cpuset.c
> @@ -1004,8 +1004,11 @@ void rebuild_sched_domains_locked(void)
>   	* prevent the panic.
>   	*/
>   	for (i = 0; doms && i < ndoms; i++) {
> -		if (WARN_ON_ONCE(!cpumask_subset(doms[i], cpu_active_mask)))
> +		if (WARN_ON_ONCE(!cpumask_subset(doms[i], cpu_active_mask))) {
> +			free_sched_domains(doms, ndoms);
> +			kfree(attr);
>   			return;
> +		}
>   	}
>   
>   	/* Have scheduler rebuild the domains */
This WARN_ON_ONCE() is mainly used to catch bug during code update. It 
shouldn't be triggered in normal use. Anyway, it is a nice-to-have fix.

Reviewed-by:  Waiman Long <longman@redhat.com>