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authorBenny Halevy <bhalevy@panasas.com>2007-05-15 04:15:27 -0400
committerGreg Kroah-Hartman <gregkh@suse.de>2007-07-12 19:34:31 -0400
commit52f6b5e1f15fa8c06efa69a4b5faa69c04707c92 (patch)
tree3918f4d76adad79172ce42de5691bfc8c4781d40
parentefdff60885e36b5091cdc47742dd5768ff4119be (diff)
synchronization in usb_serial_put
I think there is a race between usb_serial_put() and usb_serial_get_by_index() (and get_free_serial()) with regards to handling the serial port refcount. usb_serial_get_by_index() gets a reference on the serial port under table_lock while return_serial releases all the returned ports from the table under the same lock. However, the table_lock is not taken around the call to kref_put, theoretically allowing to sneak in and grab a reference after kref_put has already determined that the reference count is zero (and before calling destroy_serial) causing use after free. Signed-off-by: Benny Halevy <bhalevy@ns1.bhalevy.com> Cc: Oliver Neukum <oneukum@suse.de> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
-rw-r--r--drivers/usb/serial/usb-serial.c4
1 files changed, 2 insertions, 2 deletions
diff --git a/drivers/usb/serial/usb-serial.c b/drivers/usb/serial/usb-serial.c
index e3e3728e16e3..a3665659d13b 100644
--- a/drivers/usb/serial/usb-serial.c
+++ b/drivers/usb/serial/usb-serial.c
@@ -122,11 +122,9 @@ static void return_serial(struct usb_serial *serial)
122 if (serial == NULL) 122 if (serial == NULL)
123 return; 123 return;
124 124
125 spin_lock(&table_lock);
126 for (i = 0; i < serial->num_ports; ++i) { 125 for (i = 0; i < serial->num_ports; ++i) {
127 serial_table[serial->minor + i] = NULL; 126 serial_table[serial->minor + i] = NULL;
128 } 127 }
129 spin_unlock(&table_lock);
130} 128}
131 129
132static void destroy_serial(struct kref *kref) 130static void destroy_serial(struct kref *kref)
@@ -174,7 +172,9 @@ static void destroy_serial(struct kref *kref)
174 172
175void usb_serial_put(struct usb_serial *serial) 173void usb_serial_put(struct usb_serial *serial)
176{ 174{
175 spin_lock(&table_lock);
177 kref_put(&serial->kref, destroy_serial); 176 kref_put(&serial->kref, destroy_serial);
177 spin_unlock(&table_lock);
178} 178}
179 179
180/***************************************************************************** 180/*****************************************************************************