Messages in this thread Patch in this message | | | From | Thilo-Alexander Ginkel <> | Subject | [PATCH 1/1] usb: cdc-acm: Fix acm_tty_hangup() vs. acm_tty_close() race | Date | Sat, 17 Dec 2011 10:55:10 +0100 |
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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> --- 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 a8078d0..97f2e58 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); } -- 1.7.5.4
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