usb: gadget: return the right length in ffs_epfile_io()

When the request length is aligned to maxpacketsize, sometimes
the return length ret > the user space requested len.

At that time, we will use min_t(size_t, ret, len) to limit the
size in case of user data buffer overflow.

But we need return the min_t(size_t, ret, len) to tell the user
space rightly also.

[ balbi@ti.com: also fix comment's indentation ]

Acked-by: Michal Nazarewicz <mina86@mina86.com>
Reviewed-by: David Cohen <david.a.cohen@linux.intel.com>
Signed-off-by: Chuansheng Liu <chuansheng.liu@intel.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>

1 files changed, 15 insertions, 13 deletions

diff --git a/drivers/usb/gadget/f_fs.c b/drivers/usb/gadget/f_fs.c
index 42f7a0e4be59..b2e922dcb404 100644
--- a/drivers/usb/gadget/f_fs.c
+++ b/drivers/usb/gadget/f_fs.c
@@ -838,19 +838,21 @@ static ssize_t ffs_epfile_io(struct file *file, struct ffs_io_data *io_data)
                                 ret = -EINTR;
                                 usb_ep_dequeue(ep->ep, req);
                         } else {
-                        /*
-                         * XXX We may end up silently droping data here.
-                         * Since data_len (i.e. req->length) may be bigger
-                         * than len (after being rounded up to maxpacketsize),
-                         * we may end up with more data then user space has
-                         * space for.
-                         */
-                        ret = ep->status;
-                        if (io_data->read && ret > 0 &&
-                            unlikely(copy_to_user(io_data->buf, data,
-                                                  min_t(size_t, ret,
-                                                  io_data->len))))
-                                ret = -EFAULT;
+                                /*
+                                 * XXX We may end up silently droping data
+                                 * here.  Since data_len (i.e. req->length) may
+                                 * be bigger than len (after being rounded up
+                                 * to maxpacketsize), we may end up with more
+                                 * data then user space has space for.
+                                 */
+                                ret = ep->status;
+                                if (io_data->read && ret > 0) {
+                                        ret = min_t(size_t, ret, io_data->len);
+
+                                        if (unlikely(copy_to_user(io_data->buf,
+                                                data, ret)))
+                                                ret = -EFAULT;
+                                }
                         }
                         kfree(data);
                 }