Re: [PATCH 2/4] fs/resctrl: Free mon_data structures on rdt_get_tree() failure

["Luck, Tony" <tony.luck@intel.com>]

On Fri, May 08, 2026 at 11:21:41AM -0700, Tony Luck wrote:
> If mkdir_mondata_all() succeeds but a subsequent call in rdt_get_tree()
> fails, the mon_data structures allocated by mon_get_kn_priv() are
> leaked. Add mon_put_kn_priv() to the out_mondata error path to free
> them.
> 
> mon_get_kn_priv() and mon_put_kn_priv() moved so defined before used.

My bad, leaving this stale commit comment here. Code rearrangement
in patch 1 covered this.

> Fixes: ee4f0ec938ad ("fs/resctrl: Simplify allocation of mon_data structures")
> Reported-by: Reinette Chatre <reinette.chatre@intel.com>
> Assisted-by: GitHub_Copilot_CLI:claude-sonnet-4.6

Hmmm. I don't think I was assisted at all. Actively sabotaged with a
patch that looks plausible, but it actually wrong seems more accurate.

> Signed-off-by: Tony Luck <tony.luck@intel.com>
> ---
>  fs/resctrl/rdtgroup.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/fs/resctrl/rdtgroup.c b/fs/resctrl/rdtgroup.c
> index a6376a3fc4c3..0db1a92aefbe 100644
> --- a/fs/resctrl/rdtgroup.c
> +++ b/fs/resctrl/rdtgroup.c
> @@ -3067,8 +3067,10 @@ static int rdt_get_tree(struct fs_context *fc)
>  out_psl:
>  	rdt_pseudo_lock_release();
>  out_mondata:
> -	if (resctrl_arch_mon_capable())
> +	if (resctrl_arch_mon_capable()) {
> +		mon_put_kn_priv();

Claude put this call here ...

>  		kernfs_remove(kn_mondata);
> +	}
>  out_mongrp:
>  	if (resctrl_arch_mon_capable()) {

But it really ought to be here.

>  		rdtgroup_unassign_cntrs(&rdtgroup_default);
> -- 
> 2.54.0

Claude is fired. Replacement patch below.

-Tony

From 0263035539f805f5d4bddcef8968b551354cb86d Mon Sep 17 00:00:00 2001
From: Tony Luck <tony.luck@intel.com>
Date: Thu, 7 May 2026 13:48:51 -0700
Subject: [PATCH] fs/resctrl: Free mon_data structures on rdt_get_tree()
 failure

If mkdir_mondata_all() succeeds but a subsequent call in rdt_get_tree()
fails, the mon_data structures allocated by mon_get_kn_priv() are
leaked. Add mon_put_kn_priv() to the out_mongrp error path to free
them.

Fixes: ee4f0ec938ad ("fs/resctrl: Simplify allocation of mon_data structures")
Reported-by: Reinette Chatre <reinette.chatre@intel.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>
---
 fs/resctrl/rdtgroup.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/fs/resctrl/rdtgroup.c b/fs/resctrl/rdtgroup.c
index a6376a3fc4c3..506b40dc9430 100644
--- a/fs/resctrl/rdtgroup.c
+++ b/fs/resctrl/rdtgroup.c
@@ -3071,6 +3071,7 @@ static int rdt_get_tree(struct fs_context *fc)
 		kernfs_remove(kn_mondata);
 out_mongrp:
 	if (resctrl_arch_mon_capable()) {
+		mon_put_kn_priv();
 		rdtgroup_unassign_cntrs(&rdtgroup_default);
 		kernfs_remove(kn_mongrp);
 	}
-- 
2.54.0

>