unshare: fix nsproxy leak in ksys_unshare() on set_cred_ucounts() failure

When set_cred_ucounts() fails in ksys_unshare() new_nsproxy is leaked.

Let's call put_nsproxy() if that happens.

Link: https://lkml.kernel.org/r/[email protected]
Fixes: 905ae01c4a ("Add a reference to ucounts for each cred")
Signed-off-by: Michal Grzedzicki <[email protected]>
Reviewed-by: Andrew Morton <[email protected]>
Cc: Alexey Gladkov (Intel) <[email protected]>
Cc: Ben Segall <[email protected]>
Cc: David Hildenbrand <[email protected]>
Cc: Dietmar Eggemann <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: Juri Lelli <[email protected]>
Cc: Kees Cook <[email protected]>
Cc: "Liam R. Howlett" <[email protected]>
Cc: Lorenzo Stoakes (Oracle) <[email protected]>
Cc: Mel Gorman <[email protected]>
Cc: Michal Hocko <[email protected]>
Cc: Mike Rapoport <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Steven Rostedt <[email protected]>
Cc: Suren Baghdasaryan <[email protected]>
Cc: Valentin Schneider <[email protected]>
Cc: Vincent Guittot <[email protected]>
Cc: Vlastimil Babka <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>

kernel/fork.c

@@ -3174,11 +3174,10 @@ int ksys_unshare(unsigned long unshare_flags)
 					 new_cred, new_fs);
 	if (err)
 		goto bad_unshare_cleanup_cred;
-
 	if (new_cred) {
 		err = set_cred_ucounts(new_cred);
 		if (err)
-			goto bad_unshare_cleanup_cred;
+			goto bad_unshare_cleanup_nsproxy;
 	}
 
 	if (new_fs || new_fd || do_sysvsem || new_cred || new_nsproxy) {
@@ -3194,8 +3193,10 @@ int ksys_unshare(unsigned long unshare_flags)
 			shm_init_task(current);
 		}
 
-		if (new_nsproxy)
+		if (new_nsproxy) {
 			switch_task_namespaces(current, new_nsproxy);
+			new_nsproxy = NULL;
+		}
 
 		task_lock(current);
 
@@ -3224,13 +3225,15 @@ int ksys_unshare(unsigned long unshare_flags)
 
 	perf_event_namespaces(current);
 
+bad_unshare_cleanup_nsproxy:
+	if (new_nsproxy)
+		put_nsproxy(new_nsproxy);
 bad_unshare_cleanup_cred:
 	if (new_cred)
 		put_cred(new_cred);
 bad_unshare_cleanup_fd:
 	if (new_fd)
 		put_files_struct(new_fd);
-
 bad_unshare_cleanup_fs:
 	if (new_fs)
 		free_fs_struct(new_fs);