[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>

diff --git a/drivers/usb/gadget/file_storage.c b/drivers/usb/gadget/file_storage.c
index 241c570..86a6aeb 100644 (file)
--- 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);