linux-kernel - [PATCH] unshare: Fix nsproxy leak on set_cred

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Message-ID: <20251118064552.936962-1-ptikhomirov@virtuozzo.com>
Date: Tue, 18 Nov 2025 14:45:50 +0800
From: Pavel Tikhomirov <ptikhomirov@...tuozzo.com>
To: Ingo Molnar <mingo@...hat.com>
Cc: Peter Zijlstra <peterz@...radead.org>,
	Juri Lelli <juri.lelli@...hat.com>,
	Vincent Guittot <vincent.guittot@...aro.org>,
	Dietmar Eggemann <dietmar.eggemann@....com>,
	Steven Rostedt <rostedt@...dmis.org>,
	Ben Segall <bsegall@...gle.com>,
	Mel Gorman <mgorman@...e.de>,
	Valentin Schneider <vschneid@...hat.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	David Hildenbrand <david@...nel.org>,
	Lorenzo Stoakes <lorenzo.stoakes@...cle.com>,
	"Liam R. Howlett" <Liam.Howlett@...cle.com>,
	Vlastimil Babka <vbabka@...e.cz>,
	Mike Rapoport <rppt@...nel.org>,
	Suren Baghdasaryan <surenb@...gle.com>,
	Michal Hocko <mhocko@...e.com>,
	Kees Cook <kees@...nel.org>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Alexey Gladkov <legion@...nel.org>,
	linux-kernel@...r.kernel.org,
	linux-mm@...ck.org,
	Pavel Tikhomirov <ptikhomirov@...tuozzo.com>
Subject: [PATCH] unshare: Fix nsproxy leak on set_cred_ucounts() error path

If unshare_nsproxy_namespaces() successfully creates the new_nsproxy,
but then set_cred_ucounts() fails, on its error path there is no cleanup
for new_nsproxy, so it is leaked. Let's fix that by freeing new_nsproxy
if it's not NULL on this error path.

Fixes: 905ae01c4ae2a ("Add a reference to ucounts for each cred")
Signed-off-by: Pavel Tikhomirov <ptikhomirov@...tuozzo.com>
---
 kernel/fork.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/kernel/fork.c b/kernel/fork.c
index 3da0f08615a95..6f7332e3e0c8c 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -3133,8 +3133,11 @@ int ksys_unshare(unsigned long unshare_flags)
 
 	if (new_cred) {
 		err = set_cred_ucounts(new_cred);
-		if (err)
+		if (err) {
+			if (new_nsproxy)
+				free_nsproxy(new_nsproxy);
 			goto bad_unshare_cleanup_cred;
+		}
 	}
 
 	if (new_fs || new_fd || do_sysvsem || new_cred || new_nsproxy) {
-- 
2.51.1