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authorGaurav Kohli <gkohli@codeaurora.org>2018-01-23 13:16:34 +0530
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2018-02-03 17:05:41 +0100
commit55eaecffe3d663d02084023b9fc06d5f39b97389 (patch)
tree22de3c04e0e672a4943fa2723633d70c4f3a46af /drivers
parent383e0620b70bc654619c12faf3fd3b2384a42a4c (diff)
tty: fix data race between tty_init_dev and flush of buf
commit b027e2298bd588d6fa36ed2eda97447fb3eac078 upstream. 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 <gkohli@codeaurora.org> Reviewed-by: Alan Cox <alan@linux.intel.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'drivers')
-rw-r--r--drivers/tty/tty_io.c8
-rw-r--r--drivers/tty/tty_ldisc.c4
2 files changed, 9 insertions, 3 deletions
diff --git a/drivers/tty/tty_io.c b/drivers/tty/tty_io.c
index 734a635e7363..8d9f9a803b42 100644
--- a/drivers/tty/tty_io.c
+++ b/drivers/tty/tty_io.c
@@ -1543,6 +1543,9 @@ struct tty_struct *tty_init_dev(struct tty_driver *driver, int idx)
"%s: %s driver does not set tty->port. This will crash the kernel later. Fix the driver!\n",
__func__, tty->driver->name);
+ retval = tty_ldisc_lock(tty, 5 * HZ);
+ if (retval)
+ goto err_release_lock;
tty->port->itty = tty;
/*
@@ -1553,6 +1556,7 @@ struct tty_struct *tty_init_dev(struct tty_driver *driver, int idx)
retval = tty_ldisc_setup(tty, tty->link);
if (retval)
goto err_release_tty;
+ tty_ldisc_unlock(tty);
/* Return the tty locked so that it cannot vanish under the caller */
return tty;
@@ -1565,9 +1569,11 @@ err_module_put:
/* call the tty release_tty routine to clean out this slot */
err_release_tty:
- tty_unlock(tty);
+ tty_ldisc_unlock(tty);
tty_info_ratelimited(tty, "ldisc open failed (%d), clearing slot %d\n",
retval, idx);
+err_release_lock:
+ tty_unlock(tty);
release_tty(tty, idx);
return ERR_PTR(retval);
}
diff --git a/drivers/tty/tty_ldisc.c b/drivers/tty/tty_ldisc.c
index b0500a0a87b8..3a9e2a2fd4c6 100644
--- a/drivers/tty/tty_ldisc.c
+++ b/drivers/tty/tty_ldisc.c
@@ -336,7 +336,7 @@ static inline void __tty_ldisc_unlock(struct tty_struct *tty)
ldsem_up_write(&tty->ldisc_sem);
}
-static int tty_ldisc_lock(struct tty_struct *tty, unsigned long timeout)
+int tty_ldisc_lock(struct tty_struct *tty, unsigned long timeout)
{
int ret;
@@ -347,7 +347,7 @@ static int tty_ldisc_lock(struct tty_struct *tty, unsigned long timeout)
return 0;
}
-static void tty_ldisc_unlock(struct tty_struct *tty)
+void tty_ldisc_unlock(struct tty_struct *tty)
{
clear_bit(TTY_LDISC_HALTED, &tty->flags);
__tty_ldisc_unlock(tty);