Re: [patch] netiucv: silence an underflow warning

[Ursula Braun]

Hi Dan,

thanks for reporting this netiucv-problem. There is an implication: 
Without fix, buffer values between 2**31 and 2**32 are not detected as 
invalid values. Your fix would help, but since we have to touch the 
code, I suggest to modernize it, moving from simple_strtoul() to 
kstrtouint(). This would be the patch I have in mind:

--- a/drivers/s390/net/netiucv.c
+++ b/drivers/s390/net/netiucv.c
@@ -1564,21 +1564,21 @@ static ssize_t buffer_write (struct devi
 {
        struct netiucv_priv *priv = dev_get_drvdata(dev);
        struct net_device *ndev = priv->conn->netdev;
-       char         *e;
-       int          bs1;
+       unsigned int bs1;
+       int rc;

        IUCV_DBF_TEXT(trace, 3, __func__);
        if (count >= 39)
                return -EINVAL;

-       bs1 = simple_strtoul(buf, &e, 0);
+       rc = kstrtouint(buf, 0, &bs1);

-       if (e && (!isspace(*e))) {
-               IUCV_DBF_TEXT_(setup, 2, "buffer_write: invalid char %02x\n",
-                       *e);
+       if (rc == -EINVAL) {
+               IUCV_DBF_TEXT_(setup, 2, "buffer_write: invalid char %s\n",
+                       buf);
                return -EINVAL;
        }
-       if (bs1 > NETIUCV_BUFSIZE_MAX) {
+       if ((rc == -ERANGE) || (bs1 > NETIUCV_BUFSIZE_MAX)) {
                IUCV_DBF_TEXT_(setup, 2,
                        "buffer_write: buffer size %d too large\n",
                        bs1);

And a question about your static checker detecting this problem: Is it a 
private checker, or something we could use as well?
Does your checker like my patch version?

Thanks, Ursula

On 07/14/2016 01:30 PM, Dan Carpenter wrote:
I haven't looked at the implications but we accidentally allow bs1 to
be negative.  It makes my static checker complain.

Signed-off-by: Dan Carpenter <dan.carpen...@oracle.com>

diff --git a/drivers/s390/net/netiucv.c b/drivers/s390/net/netiucv.c
index b0e8ffd..85a5744 100644
--- a/drivers/s390/net/netiucv.c
+++ b/drivers/s390/net/netiucv.c
@@ -1578,7 +1578,7 @@ static ssize_t buffer_write (struct device *dev, struct 
device_attribute *attr,
                        *e);
                return -EINVAL;
        }
-       if (bs1 > NETIUCV_BUFSIZE_MAX) {
+       if (bs1 < 0 || bs1 > NETIUCV_BUFSIZE_MAX) {
                IUCV_DBF_TEXT_(setup, 2,
                        "buffer_write: buffer size %d too large\n",
                        bs1);