From b027e2298bd588d6fa36ed2eda97447fb3eac078 Mon Sep 17 00:00:00 2001 From: Gaurav Kohli Date: Tue, 23 Jan 2018 13:16:34 +0530 Subject: tty: fix data race between tty_init_dev and flush of buf There can be a race, if receive_buf call comes before tty initialization completes in n_tty_open and tty->disc_data may be NULL. CPU0 CPU1 ---- ---- 000|n_tty_receive_buf_common() n_tty_open() -001|n_tty_receive_buf2() tty_ldisc_open.isra.3() -002|tty_ldisc_receive_buf(inline) tty_ldisc_setup() Using ldisc semaphore lock in tty_init_dev till disc_data initializes completely. Signed-off-by: Gaurav Kohli Reviewed-by: Alan Cox Cc: stable Signed-off-by: Greg Kroah-Hartman --- include/linux/tty.h | 2 ++ 1 file changed, 2 insertions(+) (limited to 'include') diff --git a/include/linux/tty.h b/include/linux/tty.h index 7ac8ba208b1f..0a6c71e0ad01 100644 --- a/include/linux/tty.h +++ b/include/linux/tty.h @@ -405,6 +405,8 @@ extern const char *tty_name(const struct tty_struct *tty); extern struct tty_struct *tty_kopen(dev_t device); extern void tty_kclose(struct tty_struct *tty); extern int tty_dev_name_to_number(const char *name, dev_t *number); +extern int tty_ldisc_lock(struct tty_struct *tty, unsigned long timeout); +extern void tty_ldisc_unlock(struct tty_struct *tty); #else static inline void tty_kref_put(struct tty_struct *tty) { } -- cgit v1.2.3