[PATCH] USB: gadget: f_fs: fix memdup_user.cocci warnings

[kernel test robot]

From: kernel test robot <l...@intel.com>

drivers/usb/gadget/function/f_fs.c:3829:8-15: WARNING opportunity for 
memdup_user

 Use memdup_user rather than duplicating its implementation
 This is a little bit restricted to reduce false positives

Generated by: scripts/coccinelle/api/memdup_user.cocci

Fixes: 8704fd73bf56 ("USB: gadget: f_fs: remove likely/unlikely")
Reported-by: kernel test robot <l...@intel.com>
Signed-off-by: kernel test robot <l...@intel.com>
---

tree:   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git 
master
head:   144c79ef33536b4ecb4951e07dbc1f2b7fa99d32
commit: 8704fd73bf5658bf4b827643f7f526481082d83f USB: gadget: f_fs: remove 
likely/unlikely

 f_fs.c |   11 +++--------
 1 file changed, 3 insertions(+), 8 deletions(-)

--- a/drivers/usb/gadget/function/f_fs.c
+++ b/drivers/usb/gadget/function/f_fs.c
@@ -3826,14 +3826,9 @@ static char *ffs_prepare_buffer(const ch
        if (!len)
                return NULL;
 
-       data = kmalloc(len, GFP_KERNEL);
-       if (!data)
-               return ERR_PTR(-ENOMEM);
-
-       if (copy_from_user(data, buf, len)) {
-               kfree(data);
-               return ERR_PTR(-EFAULT);
-       }
+       data = memdup_user(buf, len);
+       if (IS_ERR(data))
+               return ERR_PTR(PTR_ERR(data));
 
        pr_vdebug("Buffer from user space:\n");
        ffs_dump_mem("", data, len);