[PATCH] cgroup/cpuset: Fix update_prstate() always returning 0 on partition errors

[PATCH] cgroup/cpuset: Fix update_prstate() always returning 0 on partition errors

[Tao Cui]

From: Tao Cui <cuitao@kylinos.cn>

update_prstate() stores the error code in cs->prs_err and transitions
the partition to an invalid state, but always returns 0. The caller
cpuset_partition_write() uses "return retval ?: nbytes", so the write
syscall always appears to succeed from userspace even when the partition
became invalid. Return -EINVAL when err is set so userspace can detect
the failure immediately.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
---
 kernel/cgroup/cpuset.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c
index 591e3aa487fc..8605b4da610e 100644
--- a/kernel/cgroup/cpuset.c
+++ b/kernel/cgroup/cpuset.c
@@ -2965,7 +2965,7 @@ static int update_prstate(struct cpuset *cs, int new_prs)
 	if (force_sd_rebuild)
 		rebuild_sched_domains_locked();
 	free_tmpmasks(&tmpmask);
-	return 0;
+	return err ? -EINVAL : 0;
 }
 
 static struct cpuset *cpuset_attach_old_cs;
-- 
2.43.0

Re: [PATCH] cgroup/cpuset: Fix update_prstate() always returning 0 on partition errors

[Tao Cui]

Kindly disregard this patch. 
The issue is fixed by AI auto-testing without Signed-off-by; the tag will be included in v2.

在 2026/6/2 12:36, Tao Cui 写道:
> From: Tao Cui <cuitao@kylinos.cn>
> 
> update_prstate() stores the error code in cs->prs_err and transitions
> the partition to an invalid state, but always returns 0. The caller
> cpuset_partition_write() uses "return retval ?: nbytes", so the write
> syscall always appears to succeed from userspace even when the partition
> became invalid. Return -EINVAL when err is set so userspace can detect
> the failure immediately.
> 
> Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
> ---
>  kernel/cgroup/cpuset.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c
> index 591e3aa487fc..8605b4da610e 100644
> --- a/kernel/cgroup/cpuset.c
> +++ b/kernel/cgroup/cpuset.c
> @@ -2965,7 +2965,7 @@ static int update_prstate(struct cpuset *cs, int new_prs)
>  	if (force_sd_rebuild)
>  		rebuild_sched_domains_locked();
>  	free_tmpmasks(&tmpmask);
> -	return 0;
> +	return err ? -EINVAL : 0;
>  }
>  
>  static struct cpuset *cpuset_attach_old_cs;