1 files changed, 16 insertions, 0 deletions

diff --git a/net/wireless/wext-core.c b/net/wireless/wext-core.c
index 0ef17bc42bac..8f5116f5af19 100644
--- a/net/wireless/wext-core.c
+++ b/net/wireless/wext-core.c
@@ -782,6 +782,22 @@ static int ioctl_standard_iw_point(struct iw_point *iwp, unsigned int cmd,
                 }
         }
 
+        if (IW_IS_GET(cmd) && !(descr->flags & IW_DESCR_FLAG_NOMAX)) {
+                /*
+                 * If this is a GET, but not NOMAX, it means that the extra
+                 * data is not bounded by userspace, but by max_tokens. Thus
+                 * set the length to max_tokens. This matches the extra data
+                 * allocation.
+                 * The driver should fill it with the number of tokens it
+                 * provided, and it may check iwp->length rather than having
+                 * knowledge of max_tokens. If the driver doesn't change the
+                 * iwp->length, this ioctl just copies back max_token tokens
+                 * filled with zeroes. Hopefully the driver isn't claiming
+                 * them to be valid data.
+                 */
+                iwp->length = descr->max_tokens;
+        }
+
         err = handler(dev, info, (union iwreq_data *) iwp, extra);
 
         iwp->length += essid_compat;