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virtio_console: fix sparse warnings

PATCH In review Michael S. Tsirkin 2 participants 2 messages Dec 1, 2014 – Feb 3, 2015

Subsystems (3)
Char and misc drivers virtio core virtio console driver
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Michael S. Tsirkin

author maintainer
#0 lore raw

PATCH 1/1 virtio_console: fix sparse warnings

CHECK drivers/char/virtio_console.c drivers/char/virtio_console.c:687:36: warning: incorrect type in
argument 1 (different address spaces)
drivers/char/virtio_console.c:687:36: expected void [noderef]

	<asn:1>*to

drivers/char/virtio_console.c:687:36: got char *out_buf
drivers/char/virtio_console.c:790:35: warning: incorrect type in
argument 2 (different address spaces)
drivers/char/virtio_console.c:790:35: expected char *out_buf
drivers/char/virtio_console.c:790:35: got char [noderef]

	<asn:1>*ubuf

fill_readbuf is reused with both kernel and userspace pointers, depending on value of to_user flag.

Tag address parameter as __user, and cast to/from regular pointer type when we know it's safe.

Signed-off-by Michael S. Tsirkin <[email protected]>
---
 drivers/char/virtio_console.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)
drivers/char/virtio_console.c +5 -4
index 775c898..ccb5357 100644
@@ -669,8 +669,8 @@ done:
  * Give out the data that's requested from the buffer that we have
  * queued up.
  */
-static ssize_t fill_readbuf(struct port *port, char *out_buf, size_t out_count,
-			    bool to_user)
+static ssize_t fill_readbuf(struct port *port, char __user *out_buf,
+			    size_t out_count, bool to_user)
 {
 	struct port_buffer *buf;
 	unsigned long flags;

@@ -688,7 +688,8 @@ static ssize_t fill_readbuf(struct port *port, char *out_buf, size_t out_count,
 		if (ret)
 			return -EFAULT;
 	} else {
-		memcpy(out_buf, buf->buf + buf->offset, out_count);
+		memcpy((__force char *)out_buf, buf->buf + buf->offset,
+		       out_count);
 	}
 
 	buf->offset += out_count;

@@ -1162,7 +1163,7 @@ static int get_chars(u32 vtermno, char *buf, int count)
 	/* If we don't have an input queue yet, we can't get input. */
 	BUG_ON(!port->in_vq);
 
-	return fill_readbuf(port, buf, count, false);
+	return fill_readbuf(port, (__force char __user *)buf, count, false);
 }
 
 static void resize_console(struct port *port)
Signature · 1 line
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#1 lore raw
Quoted 10 lines · Michael S. Tsirkin

CHECK drivers/char/virtio_console.c drivers/char/virtio_console.c:687:36: warning: incorrect type in
argument 1 (different address spaces)
drivers/char/virtio_console.c:687:36: expected void [noderef]

	<asn:1>*to

drivers/char/virtio_console.c:687:36: got char *out_buf
drivers/char/virtio_console.c:790:35: warning: incorrect type in
argument 2 (different address spaces)
drivers/char/virtio_console.c:790:35: expected char *out_buf
drivers/char/virtio_console.c:790:35: got char [noderef]

Quoted 4 lines
	<asn:1>*ubuf

fill_readbuf is reused with both kernel and userspace pointers, depending on value of to_user flag.

That's horrid, don't do that. Have two different functions for this type of thing, otherwise you defeat the whole purpose of trying to track __user pointers.

thanks,

greg k-h