[PATCH] g_file_storage: fix obscure race condition

This patch (as575) fixes an unlikely race in the g_file_storage driver.
The problem can occur only when the driver is unbound before its
initialization routine has finished.

I also took the opportunity to replace kmalloc/memset with kzalloc.

Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

1 files changed, 9 insertions, 12 deletions

diff --git a/drivers/usb/gadget/file_storage.c b/drivers/usb/gadget/file_storage.c
index 241c570e541..86a6aeb9ed7 100644
--- a/drivers/usb/gadget/file_storage.c
+++ b/drivers/usb/gadget/file_storage.c
@@ -3823,12 +3823,11 @@ static int __init fsg_bind(struct usb_gadget *gadget)
 
         /* Create the LUNs, open their backing files, and register the
          * LUN devices in sysfs. */
-        fsg->luns = kmalloc(i * sizeof(struct lun), GFP_KERNEL);
+        fsg->luns = kzalloc(i * sizeof(struct lun), GFP_KERNEL);
         if (!fsg->luns) {
                 rc = -ENOMEM;
                 goto out;
         }
-        memset(fsg->luns, 0, i * sizeof(struct lun));
         fsg->nluns = i;
 
         for (i = 0; i < fsg->nluns; ++i) {
@@ -3989,6 +3988,11 @@ static int __init fsg_bind(struct usb_gadget *gadget)
                         mod_data.removable, mod_data.can_stall,
                         mod_data.buflen);
         DBG(fsg, "I/O thread pid: %d\n", fsg->thread_task->pid);
+
+        set_bit(REGISTERED, &fsg->atomic_bitflags);
+
+        /* Tell the thread to start working */
+        wake_up_process(fsg->thread_task);
         return 0;
 
 autoconf_fail:
@@ -4051,10 +4055,9 @@ static int __init fsg_alloc(void)
 {
         struct fsg_dev          *fsg;
 
-        fsg = kmalloc(sizeof *fsg, GFP_KERNEL);
+        fsg = kzalloc(sizeof *fsg, GFP_KERNEL);
         if (!fsg)
                 return -ENOMEM;
-        memset(fsg, 0, sizeof *fsg);
         spin_lock_init(&fsg->lock);
         init_rwsem(&fsg->filesem);
         init_waitqueue_head(&fsg->thread_wqh);
@@ -4080,15 +4083,9 @@ static int __init fsg_init(void)
         if ((rc = fsg_alloc()) != 0)
                 return rc;
         fsg = the_fsg;
-        if ((rc = usb_gadget_register_driver(&fsg_driver)) != 0) {
+        if ((rc = usb_gadget_register_driver(&fsg_driver)) != 0)
                 fsg_free(fsg);
-                return rc;
-        }
-        set_bit(REGISTERED, &fsg->atomic_bitflags);
-
-        /* Tell the thread to start working */
-        wake_up_process(fsg->thread_task);
-        return 0;
+        return rc;
 }
 module_init(fsg_init);