netfilter: ipset: Fix an error code in ip_set_sockfn_get()

BugLink: https://bugs.launchpad.net/bugs/1852335

commit 30b7244d upstream.

The copy_to_user() function returns the number of bytes remaining to be
copied.  In this code, that positive return is checked at the end of the
function and we return zero/success.  What we should do instead is
return -EFAULT.

Fixes: a7b4f989 ("netfilter: ipset: IP set core support")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Jozsef Kadlecsik <kadlec@netfilter.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Connor Kuehl <connor.kuehl@canonical.com>
Signed-off-by: Khalid Elmously <khalid.elmously@canonical.com>

net/netfilter/ipset/ip_set_core.c

@@ -1956,8 +1956,9 @@ ip_set_sockfn_get(struct sock *sk, int optval, void __user *user, int *len)
 		}
 
 		req_version->version = IPSET_PROTOCOL;
-		ret = copy_to_user(user, req_version,
-				   sizeof(struct ip_set_req_version));
+		if (copy_to_user(user, req_version,
+				 sizeof(struct ip_set_req_version)))
+			ret = -EFAULT;
 		goto done;
 	}
 	case IP_SET_OP_GET_BYNAME: {
@@ -2014,7 +2015,8 @@ ip_set_sockfn_get(struct sock *sk, int optval, void __user *user, int *len)
 	}	/* end of switch(op) */
 
 copy:
-	ret = copy_to_user(user, data, copylen);
+	if (copy_to_user(user, data, copylen))
+		ret = -EFAULT;
 
 done:
 	vfree(data);