1 files changed, 26 insertions, 22 deletions

diff --git a/fs/proc/consoles.c b/fs/proc/consoles.c
index 290ba85cb900..b7cab1ad990d 100644
--- a/fs/proc/consoles.c
+++ b/fs/proc/consoles.c
@@ -1,7 +1,6 @@
+// SPDX-License-Identifier: GPL-2.0-only
 /*
  * Copyright (c) 2010 Werner Fink, Jiri Slaby
- *
- * Licensed under GPLv2
  */
 
 #include <linux/console.h>
@@ -22,6 +21,7 @@ static int show_console_dev(struct seq_file *m, void *v)
 		{ CON_ENABLED,		'E' },
 		{ CON_CONSDEV,		'C' },
 		{ CON_BOOT,		'B' },
+		{ CON_NBCON,		'N' },
 		{ CON_PRINTBUFFER,	'p' },
 		{ CON_BRL,		'b' },
 		{ CON_ANYTIME,		'a' },
@@ -34,7 +34,16 @@ static int show_console_dev(struct seq_file *m, void *v)
 	if (con->device) {
 		const struct tty_driver *driver;
 		int index;
+
+		/*
+		 * Take console_lock to serialize device() callback with
+		 * other console operations. For example, fg_console is
+		 * modified under console_lock when switching vt.
+		 */
+		console_lock();
 		driver = con->device(con, &index);
+		console_unlock();
+
 		if (driver) {
 			dev = MKDEV(driver->major, driver->minor_start);
 			dev += index;
@@ -50,22 +59,27 @@ static int show_console_dev(struct seq_file *m, void *v)
 	seq_printf(m, "%s%d", con->name, con->index);
 	seq_pad(m, ' ');
 	seq_printf(m, "%c%c%c (%s)", con->read ? 'R' : '-',
-			con->write ? 'W' : '-', con->unblank ? 'U' : '-',
-			flags);
+		   ((con->flags & CON_NBCON) || con->write) ? 'W' : '-',
+		   con->unblank ? 'U' : '-', flags);
 	if (dev)
 		seq_printf(m, " %4d:%d", MAJOR(dev), MINOR(dev));
 
-	seq_printf(m, "\n");
-
+	seq_putc(m, '\n');
 	return 0;
 }
 
 static void *c_start(struct seq_file *m, loff_t *pos)
+	__acquires(&console_mutex)
 {
 	struct console *con;
 	loff_t off = 0;
 
-	console_lock();
+	/*
+	 * Hold the console_list_lock to guarantee safe traversal of the
+	 * console list. SRCU cannot be used because there is no
+	 * place to store the SRCU cookie.
+	 */
+	console_list_lock();
 	for_each_console(con)
 		if (off++ == *pos)
 			break;
@@ -76,13 +90,15 @@ static void *c_start(struct seq_file *m, loff_t *pos)
 static void *c_next(struct seq_file *m, void *v, loff_t *pos)
 {
 	struct console *con = v;
+
 	++*pos;
-	return con->next;
+	return hlist_entry_safe(con->node.next, struct console, node);
 }
 
 static void c_stop(struct seq_file *m, void *v)
+	__releases(&console_mutex)
 {
-	console_unlock();
+	console_list_unlock();
 }
 
 static const struct seq_operations consoles_op = {
@@ -92,21 +108,9 @@ static const struct seq_operations consoles_op = {
 	.show	= show_console_dev
 };
 
-static int consoles_open(struct inode *inode, struct file *file)
-{
-	return seq_open(file, &consoles_op);
-}
-
-static const struct file_operations proc_consoles_operations = {
-	.open		= consoles_open,
-	.read		= seq_read,
-	.llseek		= seq_lseek,
-	.release	= seq_release,
-};
-
 static int __init proc_consoles_init(void)
 {
-	proc_create("consoles", 0, NULL, &proc_consoles_operations);
+	proc_create_seq("consoles", 0, NULL, &consoles_op);
 	return 0;
 }
 fs_initcall(proc_consoles_init);