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authorJiri Slaby <jslaby@suse.cz>2020-05-26 17:56:32 +0300
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2020-05-27 11:55:36 +0300
commit24eb2377f977fe06d84fca558f891f95bc28a449 (patch)
treec5d0a604006aec9b2ff62193243b69bb8ca382a6 /drivers/tty/hvc
parent8f065acec7573672dd15916e31d1e9b2e785566c (diff)
downloadlinux-24eb2377f977fe06d84fca558f891f95bc28a449.tar.xz
tty: hvc_console, fix crashes on parallel open/close
hvc_open sets tty->driver_data to NULL when open fails at some point. Typically, the failure happens in hp->ops->notifier_add(). If there is a racing process which tries to open such mangled tty, which was not closed yet, the process will crash in hvc_open as tty->driver_data is NULL. All this happens because close wants to know whether open failed or not. But ->open should not NULL this and other tty fields for ->close to be happy. ->open should call tty_port_set_initialized(true) and close should check by tty_port_initialized() instead. So do this properly in this driver. So this patch removes these from ->open: * tty_port_tty_set(&hp->port, NULL). This happens on last close. * tty->driver_data = NULL. Dtto. * tty_port_put(&hp->port). This happens in shutdown and until now, this must have been causing a reference underflow, if I am not missing something. Signed-off-by: Jiri Slaby <jslaby@suse.cz> Cc: stable <stable@vger.kernel.org> Reported-and-tested-by: Raghavendra <rananta@codeaurora.org> Link: https://lore.kernel.org/r/20200526145632.13879-1-jslaby@suse.cz Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'drivers/tty/hvc')
-rw-r--r--drivers/tty/hvc/hvc_console.c23
1 files changed, 8 insertions, 15 deletions
diff --git a/drivers/tty/hvc/hvc_console.c b/drivers/tty/hvc/hvc_console.c
index 436cc51c92c3..cdcc64ea2554 100644
--- a/drivers/tty/hvc/hvc_console.c
+++ b/drivers/tty/hvc/hvc_console.c
@@ -371,15 +371,14 @@ static int hvc_open(struct tty_struct *tty, struct file * filp)
* tty fields and return the kref reference.
*/
if (rc) {
- tty_port_tty_set(&hp->port, NULL);
- tty->driver_data = NULL;
- tty_port_put(&hp->port);
printk(KERN_ERR "hvc_open: request_irq failed with rc %d.\n", rc);
- } else
+ } else {
/* We are ready... raise DTR/RTS */
if (C_BAUD(tty))
if (hp->ops->dtr_rts)
hp->ops->dtr_rts(hp, 1);
+ tty_port_set_initialized(&hp->port, true);
+ }
/* Force wakeup of the polling thread */
hvc_kick();
@@ -389,22 +388,12 @@ static int hvc_open(struct tty_struct *tty, struct file * filp)
static void hvc_close(struct tty_struct *tty, struct file * filp)
{
- struct hvc_struct *hp;
+ struct hvc_struct *hp = tty->driver_data;
unsigned long flags;
if (tty_hung_up_p(filp))
return;
- /*
- * No driver_data means that this close was issued after a failed
- * hvc_open by the tty layer's release_dev() function and we can just
- * exit cleanly because the kref reference wasn't made.
- */
- if (!tty->driver_data)
- return;
-
- hp = tty->driver_data;
-
spin_lock_irqsave(&hp->port.lock, flags);
if (--hp->port.count == 0) {
@@ -412,6 +401,9 @@ static void hvc_close(struct tty_struct *tty, struct file * filp)
/* We are done with the tty pointer now. */
tty_port_tty_set(&hp->port, NULL);
+ if (!tty_port_initialized(&hp->port))
+ return;
+
if (C_HUPCL(tty))
if (hp->ops->dtr_rts)
hp->ops->dtr_rts(hp, 0);
@@ -428,6 +420,7 @@ static void hvc_close(struct tty_struct *tty, struct file * filp)
* waking periodically to check chars_in_buffer().
*/
tty_wait_until_sent(tty, HVC_CLOSE_WAIT);
+ tty_port_set_initialized(&hp->port, false);
} else {
if (hp->port.count < 0)
printk(KERN_ERR "hvc_close %X: oops, count is %d\n",