[PATCH] uhid: introduce new create event to fix 32/64-bitcompatibility issue

[Kirill A. Shutemov]

Current create event has pointer in payload. It causes problem with
32/64-bit compatibility. In particular it's not possible to use 32-bit
userspace driver with 64-bit kernel.

This patch deprecates old create event and introduce a new one. The new
create event has padding for pointer on 32-bit system to extend pointer
correctly.

Old userspace driver binaries will use old create event. It requires
simple recompile to switch to new one.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
---
 drivers/hid/uhid.c        |   31 +++++++++++++++++++++++++++++++
 include/uapi/linux/uhid.h |   24 +++++++++++++++++++++++-
 2 files changed, 54 insertions(+), 1 deletion(-)

diff --git a/drivers/hid/uhid.c b/drivers/hid/uhid.c
index 714cd8c..2f0b0e4 100644
--- a/drivers/hid/uhid.c
+++ b/drivers/hid/uhid.c
@@ -343,6 +343,34 @@ err_free:
 	return ret;
 }
 
+static int uhid_dev_old_create(struct uhid_device *uhid,
+		struct uhid_event *ev)
+{
+	struct uhid_event *new;
+
+	new = kzalloc(sizeof(new), GFP_KERNEL);
+	if (!new)
+		return -ENOMEM;
+
+	new->type = UHID_CREATE;
+	memcpy(new->u.create.name, ev->u.old_create.name, 128);
+	memcpy(new->u.create.phys, ev->u.old_create.phys, 64);
+	memcpy(new->u.create.uniq, ev->u.old_create.uniq, 64);
+
+	/* Assume kernel and userspace bitness are the same */
+	new->u.create.rd_data = ev->u.old_create.rd_data;
+
+	new->u.create.rd_size = ev->u.old_create.rd_size;
+	new->u.create.bus = ev->u.old_create.bus;
+	new->u.create.vendor = ev->u.old_create.vendor;
+	new->u.create.product = ev->u.old_create.product;
+	new->u.create.version = ev->u.old_create.version;
+	new->u.create.country = ev->u.old_create.country;
+	memcpy(ev, new, sizeof(new));
+	kfree(new);
+	return uhid_dev_create(uhid, ev);
+}
+
 static int uhid_dev_destroy(struct uhid_device *uhid)
 {
 	if (!uhid->running)
@@ -507,6 +535,9 @@ static ssize_t uhid_char_write(struct file *file, const char __user *buffer,
 	case UHID_CREATE:
 		ret = uhid_dev_create(uhid, &uhid->input_buf);
 		break;
+	case UHID_OLD_CREATE:
+		ret = uhid_dev_old_create(uhid, &uhid->input_buf);
+		break;
 	case UHID_DESTROY:
 		ret = uhid_dev_destroy(uhid);
 		break;
diff --git a/include/uapi/linux/uhid.h b/include/uapi/linux/uhid.h
index 9c6974f..bb18be8 100644
--- a/include/uapi/linux/uhid.h
+++ b/include/uapi/linux/uhid.h
@@ -23,7 +23,7 @@
 #include <linux/types.h>
 
 enum uhid_event_type {
-	UHID_CREATE,
+	UHID_OLD_CREATE,
 	UHID_DESTROY,
 	UHID_START,
 	UHID_STOP,
@@ -34,13 +34,34 @@ enum uhid_event_type {
 	UHID_INPUT,
 	UHID_FEATURE,
 	UHID_FEATURE_ANSWER,
+	UHID_CREATE,
 };
 
+struct uhid_old_create_req {
+	__u8 name[128];
+	__u8 phys[64];
+	__u8 uniq[64];
+	__u8 __user *rd_data;
+	__u16 rd_size;
+
+	__u16 bus;
+	__u32 vendor;
+	__u32 product;
+	__u32 version;
+	__u32 country;
+} __attribute__((__packed__));
+
 struct uhid_create_req {
 	__u8 name[128];
 	__u8 phys[64];
 	__u8 uniq[64];
+#if __BITS_PER_LONG != 64 && __BYTE_ORDER == __BIG_ENDIAN
+	__u32 __pad;
+#endif
 	__u8 __user *rd_data;
+#if __BITS_PER_LONG != 64 && __BYTE_ORDER == __LITTLE_ENDIAN
+	__u32 __pad;
+#endif
 	__u16 rd_size;
 
 	__u16 bus;
@@ -92,6 +113,7 @@ struct uhid_event {
 	__u32 type;
 
 	union {
+		struct uhid_old_create_req old_create;
 		struct uhid_create_req create;
 		struct uhid_input_req input;
 		struct uhid_output_req output;
-- 
 Kirill A. Shutemov
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