[PATCH 21/26] usb: gadget: composite: remove check of list iterator against head past the loop body

[Jakob Koschel]

When list_for_each_entry() completes the iteration over the whole list
without breaking the loop, the iterator value will be a bogus pointer
computed based on the head element.

While it is safe to use the pointer to determine if it was computed
based on the head element, either with list_entry_is_head() or
&pos->member == head, using the iterator variable after the loop should
be avoided.

In preparation to limiting the scope of a list iterator to the list
traversal loop, use a dedicated pointer to point to the found element [1].

Link: https://lore.kernel.org/all/YhdfEIwI4EdtHdym@xxxxxxxxx/
Signed-off-by: Jakob Koschel <jakobkoschel@xxxxxxxxx>
---
 drivers/usb/gadget/composite.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/drivers/usb/gadget/composite.c b/drivers/usb/gadget/composite.c
index 9315313108c9..26908d012ac8 100644
--- a/drivers/usb/gadget/composite.c
+++ b/drivers/usb/gadget/composite.c
@@ -1690,6 +1690,7 @@ composite_setup(struct usb_gadget *gadget, const struct usb_ctrlrequest *ctrl)
 	u16				w_value = le16_to_cpu(ctrl->wValue);
 	u16				w_length = le16_to_cpu(ctrl->wLength);
 	struct usb_function		*f = NULL;
+	struct usb_function		*tmp;
 	u8				endp;
 
 	if (w_length > USB_COMP_EP0_BUFSIZ) {
@@ -2046,12 +2047,12 @@ composite_setup(struct usb_gadget *gadget, const struct usb_ctrlrequest *ctrl)
 			if (!cdev->config)
 				break;
 			endp = ((w_index & 0x80) >> 3) | (w_index & 0x0f);
-			list_for_each_entry(f, &cdev->config->functions, list) {
-				if (test_bit(endp, f->endpoints))
+			list_for_each_entry(tmp, &cdev->config->functions, list) {
+				if (test_bit(endp, tmp->endpoints)) {
+					f = tmp;
 					break;
+				}
 			}
-			if (&f->list == &cdev->config->functions)
-				f = NULL;
 			break;
 		}
 try_fun_setup:
-- 
2.25.1