[PATCH 5/8] staging: wfx: increase robustness of hif_generic_confirm()

[Jerome Pouiller <Jerome.Pouiller@xxxxxxxxxx>]

From: Jérôme Pouiller <jerome.pouiller@xxxxxxxxxx>

Smatch complains:

    drivers/staging/wfx/hif_rx.c:26 hif_generic_confirm() warn: negative user subtract: 0-u16max - 4
    20  static int hif_generic_confirm(struct wfx_dev *wdev,
    21                                 const struct hif_msg *hif, const void *buf)
    22  {
    23          // All confirm messages start with status
    24          int status = le32_to_cpup((__le32 *)buf);
    25          int cmd = hif->id;
    26          int len = le16_to_cpu(hif->len) - 4; // drop header
                                              ^^^^^
    27
    28          WARN(!mutex_is_locked(&wdev->hif_cmd.lock), "data locking error");

In fact, rx_helper() already make the necessary checks on the value of
hif->len. Never mind, add an explicit check to make Smatch happy.

Reported-by: Dan Carpenter <dan.carpenter@xxxxxxxxxx>
Signed-off-by: Jérôme Pouiller <jerome.pouiller@xxxxxxxxxx>
---
 drivers/staging/wfx/hif_rx.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/staging/wfx/hif_rx.c b/drivers/staging/wfx/hif_rx.c
index ca09467cba05..2d4265257112 100644
--- a/drivers/staging/wfx/hif_rx.c
+++ b/drivers/staging/wfx/hif_rx.c
@@ -40,10 +40,10 @@ static int hif_generic_confirm(struct wfx_dev *wdev,
 	}
 
 	if (wdev->hif_cmd.buf_recv) {
-		if (wdev->hif_cmd.len_recv >= len)
+		if (wdev->hif_cmd.len_recv >= len && len > 0)
 			memcpy(wdev->hif_cmd.buf_recv, buf, len);
 		else
-			status = -ENOMEM;
+			status = -EIO;
 	}
 	wdev->hif_cmd.ret = status;
 
-- 
2.28.0