staging: kpc2000: prevent underflow in cpld_reconfigure()

commit 72db61d7d17a475d3cc9de1a7c871d518fcd82f0 upstream.

This function should not allow negative values of "wr_val".  If
negatives are allowed then capping the upper bound at 7 is
meaningless.  Let's make it unsigned.

Fixes: 7dc7967fc39a ("staging: kpc2000: add initial set of Daktronics drivers")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Cc: stable <stable@vger.kernel.org>
Link: https://lore.kernel.org/r/20200224103325.hrxdnaeqsthplu42@kili.mountain
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/staging/kpc2000/kpc2000/core.c b/drivers/staging/kpc2000/kpc2000/core.c
index 0a23727..8714416 100644 (file)
--- a/drivers/staging/kpc2000/kpc2000/core.c
+++ b/drivers/staging/kpc2000/kpc2000/core.c
@@ -110,10 +110,10 @@ static ssize_t cpld_reconfigure(struct device *dev,
                                const char *buf, size_t count)
 {
        struct kp2000_device *pcard = dev_get_drvdata(dev);
-       long wr_val;
+       unsigned long wr_val;
        int rv;
 
-       rv = kstrtol(buf, 0, &wr_val);
+       rv = kstrtoul(buf, 0, &wr_val);
        if (rv < 0)
                return rv;
        if (wr_val > 7)