From: Anirudh Rayabharam mail@anirudhrb.com
commit 8a12f8836145ffe37e9c8733dce18c22fb668b66 upstream
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.
Fixes: 72dc1c096c705 ("HSO: add option hso driver") Reported-by: syzbot+c49fe6089f295a05e6f8@syzkaller.appspotmail.com Tested-by: syzbot+c49fe6089f295a05e6f8@syzkaller.appspotmail.com Reviewed-by: Greg Kroah-Hartman gregkh@linuxfoundation.org Signed-off-by: Anirudh Rayabharam mail@anirudhrb.com Signed-off-by: David S. Miller davem@davemloft.net [sudip: adjust context] Signed-off-by: Sudip Mukherjee sudipm.mukherjee@gmail.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/net/usb/hso.c | 33 ++++++++++++--------------------- 1 file changed, 12 insertions(+), 21 deletions(-)
--- a/drivers/net/usb/hso.c +++ b/drivers/net/usb/hso.c @@ -626,7 +626,7 @@ static struct hso_serial *get_serial_by_ return serial; }
-static int get_free_serial_index(void) +static int obtain_minor(struct hso_serial *serial) { int index; unsigned long flags; @@ -634,8 +634,10 @@ 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); @@ -644,15 +646,12 @@ 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); }
@@ -2243,6 +2242,7 @@ static int hso_stop_serial_device(struct 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) @@ -2267,25 +2267,23 @@ static int hso_serial_common_create(stru int rx_size, int tx_size) { struct device *dev; - int minor; int i;
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; + } dev = serial->parent->dev;
- /* 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; @@ -2678,9 +2676,6 @@ static struct hso_device *hso_create_bul
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);
@@ -2737,9 +2732,6 @@ struct hso_device *hso_create_mux_serial 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);
@@ -3124,7 +3116,6 @@ static void hso_free_interface(struct us 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); } }