wifi: avoid kernel-infoleak from struct iw_point

struct iw_point has a 32bit hole on 64bit arches.

struct iw_point {
  void __user   *pointer;       /* Pointer to the data  (in user space) */
  __u16         length;         /* number of fields or size in bytes */
  __u16         flags;          /* Optional params */
};

Make sure to zero the structure to avoid disclosing 32bits of kernel data
to user space.

Fixes: 87de87d ("wext: Dispatch and handle compat ioctls entirely in net/wireless/wext.c")
Reported-by: syzbot+bfc7323743ca6dbcc3d3@syzkaller.appspotmail.com
Closes: https://lore.kernel.org/netdev/695f83f3.050a0220.1c677c.0392.GAE@google.com/T/#u
Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: stable@vger.kernel.org
Link: https://patch.msgid.link/20260108101927.857582-1-edumazet@google.com
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

Author: edumazet

net/wireless/wext-core.c

@@ -1101,6 +1101,10 @@ static int compat_standard_call(struct net_device	*dev,
 		return ioctl_standard_call(dev, iwr, cmd, info, handler);
 
 	iwp_compat = (struct compat_iw_point *) &iwr->u.data;
+
+	/* struct iw_point has a 32bit hole on 64bit arches. */
+	memset(&iwp, 0, sizeof(iwp));
+
 	iwp.pointer = compat_ptr(iwp_compat->pointer);
 	iwp.length = iwp_compat->length;
 	iwp.flags = iwp_compat->flags;

net/wireless/wext-priv.c

@@ -228,6 +228,10 @@ int compat_private_call(struct net_device *dev, struct iwreq *iwr,
 		struct iw_point iwp;
 
 		iwp_compat = (struct compat_iw_point *) &iwr->u.data;
+
+		/* struct iw_point has a 32bit hole on 64bit arches. */
+		memset(&iwp, 0, sizeof(iwp));
+
 		iwp.pointer = compat_ptr(iwp_compat->pointer);
 		iwp.length = iwp_compat->length;
 		iwp.flags = iwp_compat->flags;