V4L/DVB (7712): pvrusb2: Close connect/disconnect race

If a disconnect happens before initialization is completed, the
pvrusb2 driver can accidentally touch dangling pointers.  The whole
initialization function must be protected by the big_lock, and once
inside that lock, the initialization function should abort if it is
discovered that a disconnect has already taken place.

Signed-off-by: Mike Isely <isely@pobox.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>

1 files changed, 10 insertions, 1 deletions

diff --git a/drivers/media/video/pvrusb2/pvrusb2-hdw.c b/drivers/media/video/pvrusb2/pvrusb2-hdw.c
index 4f6bb58ca5fc..f907a56c587d 100644
--- a/drivers/media/video/pvrusb2/pvrusb2-hdw.c
+++ b/drivers/media/video/pvrusb2/pvrusb2-hdw.c
@@ -1854,10 +1854,19 @@ int pvr2_hdw_initialize(struct pvr2_hdw *hdw,
                         void *callback_data)
 {
         LOCK_TAKE(hdw->big_lock); do {
+                if (hdw->flag_disconnected) {
+                        /* Handle a race here: If we're already
+                           disconnected by this point, then give up.  If we
+                           get past this then we'll remain connected for
+                           the duration of initialization since the entire
+                           initialization sequence is now protected by the
+                           big_lock. */
+                        break;
+                }
                 hdw->state_data = callback_data;
                 hdw->state_func = callback_func;
+                pvr2_hdw_setup(hdw);
         } while (0); LOCK_GIVE(hdw->big_lock);
-        pvr2_hdw_setup(hdw);
         return hdw->flag_init_ok;
 }