| Message ID | 20210406124402.20930-1-mail@anirudhrb.com |
|---|---|
| State | Superseded |
| Headers | show |
| Series | net: hso: fix null-ptr-deref during tty device unregistration | expand |
On Tue, Apr 06, 2021 at 06:13:59PM +0530, Anirudh Rayabharam wrote: > Multiple ttys try to claim the same the minor number causing a double > unregistration of the same device. The first unregistration succeeds > but the next one results in a null-ptr-deref. > > The get_free_serial_index() function returns an available minor number > but doesn't assign it immediately. The assignment is done by the caller > later. But before this assignment, calls to get_free_serial_index() > would return the same minor number. > > Fix this by modifying get_free_serial_index to assign the minor number > immediately after one is found to be and rename it to obtain_minor() > to better reflect what it does. Similary, rename set_serial_by_index() > to release_minor() and modify it to free up the minor number of the > given hso_serial. Every obtain_minor() should have corresponding > release_minor() call. > > Reported-by: syzbot+c49fe6089f295a05e6f8@syzkaller.appspotmail.com > Tested-by: syzbot+c49fe6089f295a05e6f8@syzkaller.appspotmail.com > > Signed-off-by: Anirudh Rayabharam <mail@anirudhrb.com> Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
On Tue, Apr 06, 2021 at 04:39:21PM -0700, David Miller wrote: > From: Anirudh Rayabharam <mail@anirudhrb.com> > Date: Tue, 6 Apr 2021 18:13:59 +0530 > > > Multiple ttys try to claim the same the minor number causing a double > > unregistration of the same device. The first unregistration succeeds > > but the next one results in a null-ptr-deref. > > > > The get_free_serial_index() function returns an available minor number > > but doesn't assign it immediately. The assignment is done by the caller > > later. But before this assignment, calls to get_free_serial_index() > > would return the same minor number. > > > > Fix this by modifying get_free_serial_index to assign the minor number > > immediately after one is found to be and rename it to obtain_minor() > > to better reflect what it does. Similary, rename set_serial_by_index() > > to release_minor() and modify it to free up the minor number of the > > given hso_serial. Every obtain_minor() should have corresponding > > release_minor() call. > > > > Reported-by: syzbot+c49fe6089f295a05e6f8@syzkaller.appspotmail.com > > Tested-by: syzbot+c49fe6089f295a05e6f8@syzkaller.appspotmail.com > > > > Signed-off-by: Anirudh Rayabharam <mail@anirudhrb.com> > > This adds a new build warning: > > CC [M] drivers/net/usb/hso.o > drivers/net/usb/hso.c: In function ‘hso_serial_common_create’: > drivers/net/usb/hso.c:2256:6: warning: unused variable ‘minor’ [-Wunused-variable] > > Please fix this and add an appropriate Fixes: tag, thank you. I have sent out a v2 with these changes. Thanks! - Anirudh.
diff --git a/drivers/net/usb/hso.c b/drivers/net/usb/hso.c index 31d51346786a..295ca330e70c 100644 --- a/drivers/net/usb/hso.c +++ b/drivers/net/usb/hso.c @@ -611,7 +611,7 @@ static struct hso_serial *get_serial_by_index(unsigned index) return serial; } -static int get_free_serial_index(void) +static int obtain_minor(struct hso_serial *serial) { int index; unsigned long flags; @@ -619,8 +619,10 @@ static int get_free_serial_index(void) spin_lock_irqsave(&serial_table_lock, flags); for (index = 0; index < HSO_SERIAL_TTY_MINORS; index++) { if (serial_table[index] == NULL) { + serial_table[index] = serial->parent; + serial->minor = index; spin_unlock_irqrestore(&serial_table_lock, flags); - return index; + return 0; } } spin_unlock_irqrestore(&serial_table_lock, flags); @@ -629,15 +631,12 @@ static int get_free_serial_index(void) return -1; } -static void set_serial_by_index(unsigned index, struct hso_serial *serial) +static void release_minor(struct hso_serial *serial) { unsigned long flags; spin_lock_irqsave(&serial_table_lock, flags); - if (serial) - serial_table[index] = serial->parent; - else - serial_table[index] = NULL; + serial_table[serial->minor] = NULL; spin_unlock_irqrestore(&serial_table_lock, flags); } @@ -2230,6 +2229,7 @@ static int hso_stop_serial_device(struct hso_device *hso_dev) static void hso_serial_tty_unregister(struct hso_serial *serial) { tty_unregister_device(tty_drv, serial->minor); + release_minor(serial); } static void hso_serial_common_free(struct hso_serial *serial) @@ -2258,19 +2258,18 @@ static int hso_serial_common_create(struct hso_serial *serial, int num_urbs, tty_port_init(&serial->port); - minor = get_free_serial_index(); - if (minor < 0) + if (obtain_minor(serial)) goto exit2; /* register our minor number */ serial->parent->dev = tty_port_register_device_attr(&serial->port, - tty_drv, minor, &serial->parent->interface->dev, + tty_drv, serial->minor, &serial->parent->interface->dev, serial->parent, hso_serial_dev_groups); - if (IS_ERR(serial->parent->dev)) + if (IS_ERR(serial->parent->dev)) { + release_minor(serial); goto exit2; + } - /* fill in specific data for later use */ - serial->minor = minor; serial->magic = HSO_SERIAL_MAGIC; spin_lock_init(&serial->serial_lock); serial->num_rx_urbs = num_urbs; @@ -2667,9 +2666,6 @@ static struct hso_device *hso_create_bulk_serial_device( serial->write_data = hso_std_serial_write_data; - /* and record this serial */ - set_serial_by_index(serial->minor, serial); - /* setup the proc dirs and files if needed */ hso_log_port(hso_dev); @@ -2726,9 +2722,6 @@ struct hso_device *hso_create_mux_serial_device(struct usb_interface *interface, serial->shared_int->ref_count++; mutex_unlock(&serial->shared_int->shared_int_lock); - /* and record this serial */ - set_serial_by_index(serial->minor, serial); - /* setup the proc dirs and files if needed */ hso_log_port(hso_dev); @@ -3113,7 +3106,6 @@ static void hso_free_interface(struct usb_interface *interface) cancel_work_sync(&serial_table[i]->async_get_intf); hso_serial_tty_unregister(serial); kref_put(&serial_table[i]->ref, hso_serial_ref_free); - set_serial_by_index(i, NULL); } }