USB: gadget: g_fs: possible invalid pointer reference bug fixed

During __gfs_do_config() some invalid pointers may be left
in usb_configuration::interfaces array from previous calls
to the __gfs_do_config() for the same configuration.  This
will always happen if an user space function which has
a fewer then the last user space function registers itself.
Composite's set_config() function that a pointer after the
last interface in usb_configuration::interface is NULL
unless the array is full.

This patch makes the __gfs_do_config() make sure that if the
usb_configuration::interface is not full then a pointer
after the last interface is NULL.

Signed-off-by: Michal Nazarewicz <m.nazarewicz@samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

1 files changed, 11 insertions, 0 deletions

diff --git a/drivers/usb/gadget/g_ffs.c b/drivers/usb/gadget/g_ffs.c
index 4b0e4a040d6f..d1af253a9105 100644
--- a/drivers/usb/gadget/g_ffs.c
+++ b/drivers/usb/gadget/g_ffs.c
@@ -392,6 +392,17 @@ static int __gfs_do_config(struct usb_configuration *c,
         if (unlikely(ret < 0))
                 return ret;
 
+        /* After previous do_configs there may be some invalid
+         * pointers in c->interface array.  This happens every time
+         * a user space function with fewer interfaces than a user
+         * space function that was run before the new one is run.  The
+         * compasit's set_config() assumes that if there is no more
+         * then MAX_CONFIG_INTERFACES interfaces in a configuration
+         * then there is a NULL pointer after the last interface in
+         * c->interface array.  We need to make sure this is true. */
+        if (c->next_interface_id < ARRAY_SIZE(c->interface))
+                c->interface[c->next_interface_id] = NULL;
+
         return 0;
 }