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

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

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.

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
Signed-off-by: Tony Luck <tony.luck@intel.com>
---

Did I really need AI to help, no. But I wanted to see if it can at least
save me from some typing. Here's the prompt I used (contains just as
much typed content as this change!)

  Reinette Chatre <reinette.chatre@intel.com> reported a problem in
  rdt_get_tree(). If the mkdir_mondata_all() succeeds, the some memory
  is allocated by mon_get_kn_priv(). If a subsequent call in rdt_get_tree()
  fails, then a call to mon_put_kn_priv() is needed to free any mon_data
  structures.

  Create and apply a patch to fix this. Research a suitable Fixes: tag.
  Give credit to Reinette for reporting. Add a correctly formatted
  Assisted-by: tag with AI model version. Keep the commit comment
  concise.

 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 5dfdaa6f9d8f..aad573b62fd7 100644
--- a/fs/resctrl/rdtgroup.c
+++ b/fs/resctrl/rdtgroup.c
@@ -2879,8 +2879,10 @@ 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();
 		kernfs_remove(kn_mondata);
+	}
 out_mongrp:
 	if (resctrl_arch_mon_capable()) {
 		rdtgroup_unassign_cntrs(&rdtgroup_default);
-- 
2.54.0