linux-hardening - [PATCH v3 1/2] tty: Move sysctl setup into "core" tty logic

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Date:   Sat, 22 Oct 2022 11:29:48 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     Kees Cook <keescook@...omium.org>,
        Jiri Slaby <jirislaby@...nel.org>,
        Simon Brand <simon.brand@...tadigitale.de>,
        linux-kernel@...r.kernel.org, linux-hardening@...r.kernel.org
Subject: [PATCH v3 1/2] tty: Move sysctl setup into "core" tty logic

In preparation for adding another sysctl to the tty subsystem, move the
tty setup code into the "core" tty code, which contains tty_init() itself.

Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc: Jiri Slaby <jirislaby@...nel.org>
Signed-off-by: Kees Cook <keescook@...omium.org>
---
 drivers/tty/tty.h       |  2 +-
 drivers/tty/tty_io.c    | 34 ++++++++++++++++++++++++++++++++--
 drivers/tty/tty_ldisc.c | 38 +-------------------------------------
 3 files changed, 34 insertions(+), 40 deletions(-)

diff --git a/drivers/tty/tty.h b/drivers/tty/tty.h
index 1c08c9b67b16..f45cd683c02e 100644
--- a/drivers/tty/tty.h
+++ b/drivers/tty/tty.h
@@ -93,7 +93,7 @@ void tty_ldisc_release(struct tty_struct *tty);
 int __must_check tty_ldisc_init(struct tty_struct *tty);
 void tty_ldisc_deinit(struct tty_struct *tty);
 
-void tty_sysctl_init(void);
+extern int tty_ldisc_autoload;
 
 /* tty_audit.c */
 #ifdef CONFIG_AUDIT
diff --git a/drivers/tty/tty_io.c b/drivers/tty/tty_io.c
index de06c3c2ff70..fe77a3d41326 100644
--- a/drivers/tty/tty_io.c
+++ b/drivers/tty/tty_io.c
@@ -3572,13 +3572,44 @@ void console_sysfs_notify(void)
 		sysfs_notify(&consdev->kobj, NULL, "active");
 }
 
+static struct ctl_table tty_table[] = {
+	{
+		.procname	= "ldisc_autoload",
+		.data		= &tty_ldisc_autoload,
+		.maxlen		= sizeof(tty_ldisc_autoload),
+		.mode		= 0644,
+		.proc_handler	= proc_dointvec,
+		.extra1		= SYSCTL_ZERO,
+		.extra2		= SYSCTL_ONE,
+	},
+	{ }
+};
+
+static struct ctl_table tty_dir_table[] = {
+	{
+		.procname	= "tty",
+		.mode		= 0555,
+		.child		= tty_table,
+	},
+	{ }
+};
+
+static struct ctl_table tty_root_table[] = {
+	{
+		.procname	= "dev",
+		.mode		= 0555,
+		.child		= tty_dir_table,
+	},
+	{ }
+};
+
 /*
  * Ok, now we can initialize the rest of the tty devices and can count
  * on memory allocations, interrupts etc..
  */
 int __init tty_init(void)
 {
-	tty_sysctl_init();
+	register_sysctl_table(tty_root_table);
 	cdev_init(&tty_cdev, &tty_fops);
 	if (cdev_add(&tty_cdev, MKDEV(TTYAUX_MAJOR, 0), 1) ||
 	    register_chrdev_region(MKDEV(TTYAUX_MAJOR, 0), 1, "/dev/tty") < 0)
@@ -3600,4 +3631,3 @@ int __init tty_init(void)
 #endif
 	return 0;
 }
-
diff --git a/drivers/tty/tty_ldisc.c b/drivers/tty/tty_ldisc.c
index 776d8a62f77c..e758f44729e7 100644
--- a/drivers/tty/tty_ldisc.c
+++ b/drivers/tty/tty_ldisc.c
@@ -117,7 +117,7 @@ static void put_ldops(struct tty_ldisc_ops *ldops)
 	raw_spin_unlock_irqrestore(&tty_ldiscs_lock, flags);
 }
 
-static int tty_ldisc_autoload = IS_BUILTIN(CONFIG_LDISC_AUTOLOAD);
+int tty_ldisc_autoload = IS_BUILTIN(CONFIG_LDISC_AUTOLOAD);
 
 /**
  * tty_ldisc_get	-	take a reference to an ldisc
@@ -817,39 +817,3 @@ void tty_ldisc_deinit(struct tty_struct *tty)
 		tty_ldisc_put(tty->ldisc);
 	tty->ldisc = NULL;
 }
-
-static struct ctl_table tty_table[] = {
-	{
-		.procname	= "ldisc_autoload",
-		.data		= &tty_ldisc_autoload,
-		.maxlen		= sizeof(tty_ldisc_autoload),
-		.mode		= 0644,
-		.proc_handler	= proc_dointvec,
-		.extra1		= SYSCTL_ZERO,
-		.extra2		= SYSCTL_ONE,
-	},
-	{ }
-};
-
-static struct ctl_table tty_dir_table[] = {
-	{
-		.procname	= "tty",
-		.mode		= 0555,
-		.child		= tty_table,
-	},
-	{ }
-};
-
-static struct ctl_table tty_root_table[] = {
-	{
-		.procname	= "dev",
-		.mode		= 0555,
-		.child		= tty_dir_table,
-	},
-	{ }
-};
-
-void tty_sysctl_init(void)
-{
-	register_sysctl_table(tty_root_table);
-}
-- 
2.34.1