linux-kernel - Re: [PATCH] cgroup/cpuset: Fix a memory leak in update_exclusive

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Date: Wed, 28 Feb 2024 14:56:08 +0100
From: Mirsad Todorovac <mirsad.todorovac@....hr>
To: Waiman Long <longman@...hat.com>, Tejun Heo <tj@...nel.org>,
 Zefan Li <lizefan.x@...edance.com>, Johannes Weiner <hannes@...xchg.org>
Cc: cgroups@...r.kernel.org, linux-kernel@...r.kernel.org,
 Mirsad Todorovac <mirsad.todorovac@....hr>
Subject: Re: [PATCH] cgroup/cpuset: Fix a memory leak in
 update_exclusive_cpumask()

Hi,

On 2/28/2024 1:58 AM, Waiman Long wrote:
> Fix a possible memory leak in update_exclusive_cpumask() by moving the
> alloc_cpumasks() down after the validate_change() check which can fail
> and still before the temporary cpumasks are needed.
>
> Fixes: e2ffe502ba45 ("cgroup/cpuset: Add cpuset.cpus.exclusive for v2")
> Reported-by: Mirsad Todorovac <mirsad.todorovac@....hr>
> Closes: https://lore.kernel.org/lkml/14915689-27a3-4cd8-80d2-9c30d0c768b6@alu.unizg.hr
> Signed-off-by: Waiman Long <longman@...hat.com>
> ---
>   kernel/cgroup/cpuset.c | 6 +++---
>   1 file changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c
> index ba36c073304a..7260f095802a 100644
> --- a/kernel/cgroup/cpuset.c
> +++ b/kernel/cgroup/cpuset.c
> @@ -2598,9 +2598,6 @@ static int update_exclusive_cpumask(struct cpuset *cs, struct cpuset *trialcs,
>   	if (cpumask_equal(cs->exclusive_cpus, trialcs->exclusive_cpus))
>   		return 0;
>   
> -	if (alloc_cpumasks(NULL, &tmp))
> -		return -ENOMEM;
> -
>   	if (*buf)
>   		compute_effective_exclusive_cpumask(trialcs, NULL);
>   
> @@ -2615,6 +2612,9 @@ static int update_exclusive_cpumask(struct cpuset *cs, struct cpuset *trialcs,
>   	if (retval)
>   		return retval;
>   
> +	if (alloc_cpumasks(NULL, &tmp))
> +		return -ENOMEM;
> +
>   	if (old_prs) {
>   		if (cpumask_empty(trialcs->effective_xcpus)) {
>   			invalidate = true;Great work at such a short notice! (I failed to find the culprit myself.)

The leak is no longer present.

Please feel free to add:

Tested-by: Mirsad Todorovac <mtodorov@....unizg.hr>

Best regards, Mirsad Todorovac

P.S. APologies for the previous email accidentally sent as HTML.