[media] ngene: properly handle __user ptr

Sparse is complaining about ngene's bad usage of a __user ptr:

>> drivers/media/pci/ngene/ngene-dvb.c:62:48: sparse: incorrect type in argument 2 (different address spaces)
   drivers/media/pci/ngene/ngene-dvb.c:62:48:    expected unsigned char const [usertype] *buf
   drivers/media/pci/ngene/ngene-dvb.c:62:48:    got char const [noderef] <asn:1>*buf

As this is intercepting a .write() file ops, we can't just memcpy. We need to use
copy_from_user.

Reported-by: kbuild test robot <fengguang.wu@intel.com>
Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com>

2 files changed, 28 insertions, 0 deletions

diff --git a/drivers/media/dvb-core/dvb_ringbuffer.c b/drivers/media/dvb-core/dvb_ringbuffer.c
index a5712cd7c65f..1100e98a7b1d 100644
--- a/drivers/media/dvb-core/dvb_ringbuffer.c
+++ b/drivers/media/dvb-core/dvb_ringbuffer.c
@@ -166,6 +166,31 @@ ssize_t dvb_ringbuffer_write(struct dvb_ringbuffer *rbuf, const u8 *buf, size_t
         return len;
 }
 
+ssize_t dvb_ringbuffer_write_user(struct dvb_ringbuffer *rbuf,
+                                  const u8 __user *buf, size_t len)
+{
+        int status;
+        size_t todo = len;
+        size_t split;
+
+        split = (rbuf->pwrite + len > rbuf->size) ? rbuf->size - rbuf->pwrite : 0;
+
+        if (split > 0) {
+                status = copy_from_user(rbuf->data+rbuf->pwrite, buf, split);
+                if (status)
+                        return len - todo;
+                buf += split;
+                todo -= split;
+                rbuf->pwrite = 0;
+        }
+        status = copy_from_user(rbuf->data+rbuf->pwrite, buf, todo);
+        if (status)
+                return len - todo;
+        rbuf->pwrite = (rbuf->pwrite + todo) % rbuf->size;
+
+        return len;
+}
+
 ssize_t dvb_ringbuffer_pkt_write(struct dvb_ringbuffer *rbuf, u8* buf, size_t len)
 {
         int status;
@@ -297,3 +322,4 @@ EXPORT_SYMBOL(dvb_ringbuffer_flush_spinlock_wakeup);
 EXPORT_SYMBOL(dvb_ringbuffer_read_user);
 EXPORT_SYMBOL(dvb_ringbuffer_read);
 EXPORT_SYMBOL(dvb_ringbuffer_write);
+EXPORT_SYMBOL(dvb_ringbuffer_write_user);
diff --git a/drivers/media/dvb-core/dvb_ringbuffer.h b/drivers/media/dvb-core/dvb_ringbuffer.h
index 41f04dae69b6..9e1e11b7c39c 100644
--- a/drivers/media/dvb-core/dvb_ringbuffer.h
+++ b/drivers/media/dvb-core/dvb_ringbuffer.h
@@ -133,6 +133,8 @@ extern void dvb_ringbuffer_read(struct dvb_ringbuffer *rbuf,
 */
 extern ssize_t dvb_ringbuffer_write(struct dvb_ringbuffer *rbuf, const u8 *buf,
                                     size_t len);
+extern ssize_t dvb_ringbuffer_write_user(struct dvb_ringbuffer *rbuf,
+                                         const u8 __user *buf, size_t len);
 
 
 /**