[PATCH] bna: integer overflow bug in debugfs

[Dan Carpenter]

We could allocate less memory than intended because we do:

        bnad->regdata = kzalloc(len << 2, GFP_KERNEL);

The shift can overflow leading to a crash.  This is debugfs code so the
impact is very small.

Fixes: 7afc5dbde091 ("bna: Add debugfs interface.")
Signed-off-by: Dan Carpenter <dan.carpen...@oracle.com>

diff --git a/drivers/net/ethernet/brocade/bna/bnad_debugfs.c 
b/drivers/net/ethernet/brocade/bna/bnad_debugfs.c
index 05c1c1dd7751..cebfe3bd086e 100644
--- a/drivers/net/ethernet/brocade/bna/bnad_debugfs.c
+++ b/drivers/net/ethernet/brocade/bna/bnad_debugfs.c
@@ -325,7 +325,7 @@ bnad_debugfs_write_regrd(struct file *file, const char 
__user *buf,
                return PTR_ERR(kern_buf);
 
        rc = sscanf(kern_buf, "%x:%x", &addr, &len);
-       if (rc < 2) {
+       if (rc < 2 || len > UINT_MAX >> 2) {
                netdev_warn(bnad->netdev, "failed to read user buffer\n");
                kfree(kern_buf);
                return -EINVAL;