[PATCH 4/6] smb/server: abort initialization when proc setup fails

[ZhangGuoDong <zhang.guodong@linux.dev>]

From: ZhangGuoDong <zhangguodong@kylinos.cn>

ksmbd_server_init() calls ksmbd_proc_init() before creating the
remaining proc entries and server subsystems. ksmbd_proc_init() tears
down partial state on a procfs or percpu_counter allocation failure,
but returns void, so ksmbd_server_init() continues as if the counters
were usable.

Once userspace starts the server, server_ctrl_handle_init() calls
ksmbd_proc_reset(), which reaches percpu_counter_set() with a NULL
per-CPU counters pointer on SMP systems. The later ksmbd_proc_create()
calls also receive a NULL parent and may create entries in the /proc
root; ksmbd_proc_cleanup() cannot remove those entries because
ksmbd_proc_fs is NULL.

Fixes: b38f99c1217a ("ksmbd: add procfs interface for runtime monitoring and statistics")
Signed-off-by: ZhangGuoDong <zhangguodong@kylinos.cn>
Reviewed-by: ChenXiaoSong <chenxiaosong@kylinos.cn>
---
 fs/smb/server/misc.h   |  4 ++--
 fs/smb/server/proc.c   | 13 ++++++++-----
 fs/smb/server/server.c |  4 +++-
 3 files changed, 13 insertions(+), 8 deletions(-)

diff --git a/fs/smb/server/misc.h b/fs/smb/server/misc.h
index 680375a966c5..1faaddd0f5f7 100644
--- a/fs/smb/server/misc.h
+++ b/fs/smb/server/misc.h
@@ -43,7 +43,7 @@ struct ksmbd_const_name {
 	const char *name;
 };
 
-void ksmbd_proc_init(void);
+int ksmbd_proc_init(void);
 void ksmbd_proc_cleanup(void);
 void ksmbd_proc_reset(void);
 struct proc_dir_entry *ksmbd_proc_create(const char *name,
@@ -56,7 +56,7 @@ void ksmbd_proc_show_flag_names(struct seq_file *m,
 const char *ksmbd_proc_const_name(const struct ksmbd_const_name *table,
 				  int count, unsigned int const_value);
 #else
-static inline void ksmbd_proc_init(void) {}
+static inline int ksmbd_proc_init(void) { return 0; }
 static inline void ksmbd_proc_cleanup(void) {}
 static inline void ksmbd_proc_reset(void) {}
 #endif
diff --git a/fs/smb/server/proc.c b/fs/smb/server/proc.c
index 1bf4e00dee34..826353ed0553 100644
--- a/fs/smb/server/proc.c
+++ b/fs/smb/server/proc.c
@@ -239,14 +239,14 @@ void ksmbd_proc_reset(void)
 		percpu_counter_set(&ksmbd_counters.counters[i], 0);
 }
 
-void ksmbd_proc_init(void)
+int ksmbd_proc_init(void)
 {
 	int i;
-	int retval;
+	int retval = -ENOMEM;
 
 	ksmbd_proc_fs = proc_mkdir("fs/ksmbd", NULL);
 	if (!ksmbd_proc_fs)
-		return;
+		return retval;
 
 	if (!proc_mkdir_mode("sessions", 0400, ksmbd_proc_fs))
 		goto err_out;
@@ -257,11 +257,14 @@ void ksmbd_proc_init(void)
 			goto err_out;
 	}
 
-	if (!ksmbd_proc_create("server", proc_show_ksmbd_stats, NULL))
+	if (!ksmbd_proc_create("server", proc_show_ksmbd_stats, NULL)) {
+		retval = -ENOMEM;
 		goto err_out;
+	}
 
 	ksmbd_proc_reset();
-	return;
+	return 0;
 err_out:
 	ksmbd_proc_cleanup();
+	return retval;
 }
diff --git a/fs/smb/server/server.c b/fs/smb/server/server.c
index 18c20a669307..19630ac53235 100644
--- a/fs/smb/server/server.c
+++ b/fs/smb/server/server.c
@@ -620,7 +620,9 @@ static int __init ksmbd_server_init(void)
 		return ret;
 	}
 
-	ksmbd_proc_init();
+	ret = ksmbd_proc_init();
+	if (ret)
+		goto err_unregister;
 	create_proc_sessions();
 	create_proc_shares();
 
-- 
2.54.0