Update Linux to v5.4.2
Change-Id: Idf6911045d9d382da2cfe01b1edff026404ac8fd
diff --git a/drivers/tty/tty_ldisc.c b/drivers/tty/tty_ldisc.c
index fc4c97c..4c49f53 100644
--- a/drivers/tty/tty_ldisc.c
+++ b/drivers/tty/tty_ldisc.c
@@ -156,6 +156,13 @@
* takes tty_ldiscs_lock to guard against ldisc races
*/
+#if defined(CONFIG_LDISC_AUTOLOAD)
+ #define INITIAL_AUTOLOAD_STATE 1
+#else
+ #define INITIAL_AUTOLOAD_STATE 0
+#endif
+static int tty_ldisc_autoload = INITIAL_AUTOLOAD_STATE;
+
static struct tty_ldisc *tty_ldisc_get(struct tty_struct *tty, int disc)
{
struct tty_ldisc *ld;
@@ -170,6 +177,8 @@
*/
ldops = get_ldops(disc);
if (IS_ERR(ldops)) {
+ if (!capable(CAP_SYS_MODULE) && !tty_ldisc_autoload)
+ return ERR_PTR(-EPERM);
request_module("tty-ldisc-%d", disc);
ldops = get_ldops(disc);
if (IS_ERR(ldops))
@@ -327,6 +336,11 @@
{
int ret;
+ /* Kindly asking blocked readers to release the read side */
+ set_bit(TTY_LDISC_CHANGING, &tty->flags);
+ wake_up_interruptible_all(&tty->read_wait);
+ wake_up_interruptible_all(&tty->write_wait);
+
ret = __tty_ldisc_lock(tty, timeout);
if (!ret)
return -EBUSY;
@@ -337,6 +351,8 @@
void tty_ldisc_unlock(struct tty_struct *tty)
{
clear_bit(TTY_LDISC_HALTED, &tty->flags);
+ /* Can be cleared here - ldisc_unlock will wake up writers firstly */
+ clear_bit(TTY_LDISC_CHANGING, &tty->flags);
__tty_ldisc_unlock(tty);
}
@@ -471,6 +487,7 @@
static void tty_ldisc_close(struct tty_struct *tty, struct tty_ldisc *ld)
{
+ lockdep_assert_held_write(&tty->ldisc_sem);
WARN_ON(!test_bit(TTY_LDISC_OPEN, &tty->flags));
clear_bit(TTY_LDISC_OPEN, &tty->flags);
if (ld->ops->close)
@@ -492,6 +509,7 @@
struct tty_ldisc *disc = tty_ldisc_get(tty, ld);
int r;
+ lockdep_assert_held_write(&tty->ldisc_sem);
if (IS_ERR(disc))
return PTR_ERR(disc);
tty->ldisc = disc;
@@ -615,6 +633,7 @@
*/
static void tty_ldisc_kill(struct tty_struct *tty)
{
+ lockdep_assert_held_write(&tty->ldisc_sem);
if (!tty->ldisc)
return;
/*
@@ -662,6 +681,7 @@
struct tty_ldisc *ld;
int retval;
+ lockdep_assert_held_write(&tty->ldisc_sem);
ld = tty_ldisc_get(tty, disc);
if (IS_ERR(ld)) {
BUG_ON(disc == N_TTY);
@@ -760,6 +780,10 @@
return retval;
if (o_tty) {
+ /*
+ * Called without o_tty->ldisc_sem held, as o_tty has been
+ * just allocated and no one has a reference to it.
+ */
retval = tty_ldisc_open(o_tty, o_tty->ldisc);
if (retval) {
tty_ldisc_close(tty, tty->ldisc);
@@ -825,7 +849,44 @@
*/
void tty_ldisc_deinit(struct tty_struct *tty)
{
+ /* no ldisc_sem, tty is being destroyed */
if (tty->ldisc)
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);
+}