usb: gadget: Use u16 types for 16-bit fields

Since the beginning of time, struct usb_ep::maxpacket was a bitfield,
and when new 16-bit members were added, the convention was followed:

1da177e4c3f41 (Linus Torvalds   2005-04-16 236) unsigned maxpacket:16;
e117e742d3106 (Robert Baldyga   2013-12-13 237) unsigned maxpacket_limit:16;
a59d6b91cbca5 (Tatyana Brokhman 2011-06-28 238) unsigned max_streams:16;

However, there is no need for this as a simple u16 can be used instead,
simplifying the struct and the resulting compiler binary output. Switch
to u16 for all three, and rearrange struct slightly to minimize holes.
No change in the final size of the struct results; the 2 byte gap is
just moved to the end, as seen with pahole:

-       /* XXX 2 bytes hole, try to pack */
        ...
        /* size: 72, cachelines: 2, members: 15 */
        ...
+       /* padding: 2 */

Changing this simplifies future introspection[1] of maxpacket's type during
allocations:

drivers/usb/gadget/function/f_tcm.c:330:24: error: 'typeof' applied to a bit-field
     330 |  fu->cmd.buf = kmalloc(fu->ep_out->maxpacket, GFP_KERNEL);

Link: https://lore.kernel.org/all/202407090928.6UaOAZAJ-lkp@intel.com
Signed-off-by: Kees Cook <kees@kernel.org>
Link: https://lore.kernel.org/r/20240709154953.work.953-kees@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/include/linux/usb/gadget.h b/include/linux/usb/gadget.h
index 56dda8e1562d1f471ee4d91f6ad8b98e660fa79b..df33333650a0d943324c3169619e85162ee5717f 100644 (file)
--- a/include/linux/usb/gadget.h
+++ b/include/linux/usb/gadget.h
@@ -229,18 +229,18 @@ struct usb_ep {
 
        const char              *name;
        const struct usb_ep_ops *ops;
+       const struct usb_endpoint_descriptor    *desc;
+       const struct usb_ss_ep_comp_descriptor  *comp_desc;
        struct list_head        ep_list;
        struct usb_ep_caps      caps;
        bool                    claimed;
        bool                    enabled;
-       unsigned                maxpacket:16;
-       unsigned                maxpacket_limit:16;
-       unsigned                max_streams:16;
        unsigned                mult:2;
        unsigned                maxburst:5;
        u8                      address;
-       const struct usb_endpoint_descriptor    *desc;
-       const struct usb_ss_ep_comp_descriptor  *comp_desc;
+       u16                     maxpacket;
+       u16                     maxpacket_limit;
+       u16                     max_streams;
 };
 
 /*-------------------------------------------------------------------------*/