USB: core: remove the move buf action

The buffer size of sysfs is fixed at PAGE_SIZE, and the page offset
of the buf parameter of sysfs_emit_at() must be 0, there is no need
to manually manage the buf pointer offset.

Fixes: 711d41a ("usb: core: Use sysfs_emit_at() when showing dynamic IDs")
Reported-by: syzbot+b6445765657b5855e869@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=b6445765657b5855e869
Tested-by: syzbot+b6445765657b5855e869@syzkaller.appspotmail.com
Signed-off-by: Edward Adam Davis <eadavis@qq.com>
Link: https://lore.kernel.org/r/tencent_B32D6D8C9450EBFEEE5ACC2C7B0E6C402D0A@qq.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Author: ea1davis

drivers/usb/core/driver.c

@@ -119,11 +119,11 @@ ssize_t usb_show_dynids(struct usb_dynids *dynids, char *buf)
 	guard(mutex)(&usb_dynids_lock);
 	list_for_each_entry(dynid, &dynids->list, node)
 		if (dynid->id.bInterfaceClass != 0)
-			count += sysfs_emit_at(&buf[count], count, "%04x %04x %02x\n",
+			count += sysfs_emit_at(buf, count, "%04x %04x %02x\n",
 					   dynid->id.idVendor, dynid->id.idProduct,
 					   dynid->id.bInterfaceClass);
 		else
-			count += sysfs_emit_at(&buf[count], count, "%04x %04x\n",
+			count += sysfs_emit_at(buf, count, "%04x %04x\n",
 					   dynid->id.idVendor, dynid->id.idProduct);
 	return count;
 }