HID: uhid: make creating devices work on 64/32 systems

Unfortunately UHID interface, as it was introduced, is broken with 32 bit
userspace running on 64 bit kernels as it uses a pointer in its userspace
facing API.

Fix it by checking if we are executing compat task and munge the request
appropriately.

Reported-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>

1 files changed, 92 insertions, 3 deletions

diff --git a/drivers/hid/uhid.c b/drivers/hid/uhid.c
index 714cd8cc9579..fc307e0422af 100644
--- a/drivers/hid/uhid.c
+++ b/drivers/hid/uhid.c
@@ -11,6 +11,7 @@
  */
 
 #include <linux/atomic.h>
+#include <linux/compat.h>
 #include <linux/device.h>
 #include <linux/fs.h>
 #include <linux/hid.h>
@@ -276,6 +277,94 @@ static struct hid_ll_driver uhid_hid_driver = {
         .parse = uhid_hid_parse,
 };
 
+#ifdef CONFIG_COMPAT
+
+/* Apparently we haven't stepped on these rakes enough times yet. */
+struct uhid_create_req_compat {
+        __u8 name[128];
+        __u8 phys[64];
+        __u8 uniq[64];
+
+        compat_uptr_t rd_data;
+        __u16 rd_size;
+
+        __u16 bus;
+        __u32 vendor;
+        __u32 product;
+        __u32 version;
+        __u32 country;
+} __attribute__((__packed__));
+
+static int uhid_event_from_user(const char __user *buffer, size_t len,
+                                struct uhid_event *event)
+{
+        if (is_compat_task()) {
+                u32 type;
+
+                if (get_user(type, buffer))
+                        return -EFAULT;
+
+                if (type == UHID_CREATE) {
+                        /*
+                         * This is our messed up request with compat pointer.
+                         * It is largish (more than 256 bytes) so we better
+                         * allocate it from the heap.
+                         */
+                        struct uhid_create_req_compat *compat;
+
+                        compat = kmalloc(sizeof(*compat), GFP_KERNEL);
+                        if (!compat)
+                                return -ENOMEM;
+
+                        buffer += sizeof(type);
+                        len -= sizeof(type);
+                        if (copy_from_user(compat, buffer,
+                                           min(len, sizeof(*compat)))) {
+                                kfree(compat);
+                                return -EFAULT;
+                        }
+
+                        /* Shuffle the data over to proper structure */
+                        event->type = type;
+
+                        memcpy(event->u.create.name, compat->name,
+                                sizeof(compat->name));
+                        memcpy(event->u.create.phys, compat->phys,
+                                sizeof(compat->phys));
+                        memcpy(event->u.create.uniq, compat->uniq,
+                                sizeof(compat->uniq));
+
+                        event->u.create.rd_data = compat_ptr(compat->rd_data);
+                        event->u.create.rd_size = compat->rd_size;
+
+                        event->u.create.bus = compat->bus;
+                        event->u.create.vendor = compat->vendor;
+                        event->u.create.product = compat->product;
+                        event->u.create.version = compat->version;
+                        event->u.create.country = compat->country;
+
+                        kfree(compat);
+                        return 0;
+                }
+                /* All others can be copied directly */
+        }
+
+        if (copy_from_user(event, buffer, min(len, sizeof(*event))))
+                return -EFAULT;
+
+        return 0;
+}
+#else
+static int uhid_event_from_user(const char __user *buffer, size_t len,
+                                struct uhid_event *event)
+{
+        if (copy_from_user(event, buffer, min(len, sizeof(*event))))
+                return -EFAULT;
+
+        return 0;
+}
+#endif
+
 static int uhid_dev_create(struct uhid_device *uhid,
                            const struct uhid_event *ev)
 {
@@ -498,10 +587,10 @@ static ssize_t uhid_char_write(struct file *file, const char __user *buffer,
 
         memset(&uhid->input_buf, 0, sizeof(uhid->input_buf));
         len = min(count, sizeof(uhid->input_buf));
-        if (copy_from_user(&uhid->input_buf, buffer, len)) {
-                ret = -EFAULT;
+
+        ret = uhid_event_from_user(buffer, len, &uhid->input_buf);
+        if (ret)
                 goto unlock;
-        }
 
         switch (uhid->input_buf.type) {
         case UHID_CREATE: