diff options
| author | Thilo-Alexander Ginkel <thilo@ginkel.com> | 2011-12-17 10:55:10 +0100 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@suse.de> | 2012-01-12 11:29:46 -0800 |
| commit | f9fd8d6232137e255fc9409a81cf282817472b6f (patch) | |
| tree | d1bebc5ff8a4372ae6d44dd5b8b62005f6e33a07 | |
| parent | f60d8cd0b0e0def00c9ac54bb4becae034138484 (diff) | |
usb: cdc-acm: Fix acm_tty_hangup() vs. acm_tty_close() race
[Not upstream as it was fixed differently for 3.3 with a much more
"intrusive" rework of the driver - gregkh]
There is a race condition involving acm_tty_hangup() and acm_tty_close()
where hangup() would attempt to access tty->driver_data without proper
locking and NULL checking after close() has potentially already set it
to NULL. One possibility to (sporadically) trigger this behavior is to
perform a suspend/resume cycle with a running WWAN data connection.
This patch addresses the issue by introducing a NULL check for
tty->driver_data in acm_tty_hangup() protected by open_mutex and exiting
gracefully when hangup() is invoked on a device that has already been
closed.
Signed-off-by: Thilo-Alexander Ginkel <thilo@ginkel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
| -rw-r--r-- | drivers/usb/class/cdc-acm.c | 12 |
1 files changed, 10 insertions, 2 deletions
diff --git a/drivers/usb/class/cdc-acm.c b/drivers/usb/class/cdc-acm.c index ea5e487448b..e61d9c43e98 100644 --- a/drivers/usb/class/cdc-acm.c +++ b/drivers/usb/class/cdc-acm.c @@ -554,10 +554,18 @@ static void acm_port_down(struct acm *acm) static void acm_tty_hangup(struct tty_struct *tty) { - struct acm *acm = tty->driver_data; - tty_port_hangup(&acm->port); + struct acm *acm; + mutex_lock(&open_mutex); + acm = tty->driver_data; + + if (!acm) + goto out; + + tty_port_hangup(&acm->port); acm_port_down(acm); + +out: mutex_unlock(&open_mutex); } |