From patchwork Tue Aug 2 12:56:12 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Jason A. Donenfeld" X-Patchwork-Id: 12934623 X-Patchwork-Delegate: kuba@kernel.org Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 5CDCFC00140 for ; Tue, 2 Aug 2022 12:56:41 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236698AbiHBM4i (ORCPT ); Tue, 2 Aug 2022 08:56:38 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:40744 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S236731AbiHBM4f (ORCPT ); Tue, 2 Aug 2022 08:56:35 -0400 Received: from ams.source.kernel.org (ams.source.kernel.org [IPv6:2604:1380:4601:e00::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 9F70511A32 for ; Tue, 2 Aug 2022 05:56:34 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id EED7AB81EFE for ; Tue, 2 Aug 2022 12:56:32 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 31EF2C43142; Tue, 2 Aug 2022 12:56:31 +0000 (UTC) Authentication-Results: smtp.kernel.org; dkim=pass (1024-bit key) header.d=zx2c4.com header.i=@zx2c4.com header.b="WOJNvdBc" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=zx2c4.com; s=20210105; t=1659444990; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=/ZeVoWm0a7/DLh9vXJVxolr+PEKcOEQOX3WI7nDKWiQ=; b=WOJNvdBcy5RK6KJcLpO4tZJ/fl1CQ/o95+kqtqt+36IJPYLo35byZnYHKuyxY6VqOtRZQe 460Wm06jkN5ox3eIVks9F2u6n6G6ZEAektar50Zk+hLequ2zs6d6bAvwfp8RkrVKu4aSgV JyygSt3M+/Pdn9PfFGQulb41iQrKwG0= Received: by mail.zx2c4.com (ZX2C4 Mail Server) with ESMTPSA id fafa5dae (TLSv1.3:TLS_AES_256_GCM_SHA384:256:NO); Tue, 2 Aug 2022 12:56:30 +0000 (UTC) From: "Jason A. Donenfeld" To: kuba@kernel.org, pablo@netfilter.org, netdev@vger.kernel.org Cc: "Jason A. Donenfeld" , Linus Torvalds Subject: [PATCH next-next 3/4] wireguard: allowedips: don't corrupt stack when detecting overflow Date: Tue, 2 Aug 2022 14:56:12 +0200 Message-Id: <20220802125613.340848-4-Jason@zx2c4.com> In-Reply-To: <20220802125613.340848-1-Jason@zx2c4.com> References: <20220802125613.340848-1-Jason@zx2c4.com> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org X-Patchwork-Delegate: kuba@kernel.org In case push_rcu() and related functions are buggy, there's a WARN_ON(len >= 128), which the selftest tries to hit by being tricky. In case it is hit, we shouldn't corrupt the kernel's stack, though; otherwise it may be hard to even receive the report that it's buggy. So conditionalize the stack write based on that WARN_ON()'s return value. Note that this never *actually* happens anyway. The WARN_ON() in the first place is bounded by IS_ENABLED(DEBUG), and isn't expected to ever actually hit. This is just a debugging sanity check. Additionally, hoist the constant 128 into a named enum, MAX_ALLOWEDIPS_BITS, so that it's clear why this value is chosen. Suggested-by: Linus Torvalds Link: https://lore.kernel.org/all/CAHk-=wjJZGA6w_DxA+k7Ejbqsq+uGK==koPai3sqdsfJqemvag@mail.gmail.com/ Fixes: e7096c131e51 ("net: WireGuard secure network tunnel") Signed-off-by: Jason A. Donenfeld --- drivers/net/wireguard/allowedips.c | 9 ++++++--- drivers/net/wireguard/selftest/allowedips.c | 6 +++--- 2 files changed, 9 insertions(+), 6 deletions(-) diff --git a/drivers/net/wireguard/allowedips.c b/drivers/net/wireguard/allowedips.c index 9a4c8ff32d9d..5bf7822c53f1 100644 --- a/drivers/net/wireguard/allowedips.c +++ b/drivers/net/wireguard/allowedips.c @@ -6,6 +6,8 @@ #include "allowedips.h" #include "peer.h" +enum { MAX_ALLOWEDIPS_BITS = 128 }; + static struct kmem_cache *node_cache; static void swap_endian(u8 *dst, const u8 *src, u8 bits) @@ -40,7 +42,8 @@ static void push_rcu(struct allowedips_node **stack, struct allowedips_node __rcu *p, unsigned int *len) { if (rcu_access_pointer(p)) { - WARN_ON(IS_ENABLED(DEBUG) && *len >= 128); + if (WARN_ON(IS_ENABLED(DEBUG) && *len >= MAX_ALLOWEDIPS_BITS)) + return; stack[(*len)++] = rcu_dereference_raw(p); } } @@ -52,7 +55,7 @@ static void node_free_rcu(struct rcu_head *rcu) static void root_free_rcu(struct rcu_head *rcu) { - struct allowedips_node *node, *stack[128] = { + struct allowedips_node *node, *stack[MAX_ALLOWEDIPS_BITS] = { container_of(rcu, struct allowedips_node, rcu) }; unsigned int len = 1; @@ -65,7 +68,7 @@ static void root_free_rcu(struct rcu_head *rcu) static void root_remove_peer_lists(struct allowedips_node *root) { - struct allowedips_node *node, *stack[128] = { root }; + struct allowedips_node *node, *stack[MAX_ALLOWEDIPS_BITS] = { root }; unsigned int len = 1; while (len > 0 && (node = stack[--len])) { diff --git a/drivers/net/wireguard/selftest/allowedips.c b/drivers/net/wireguard/selftest/allowedips.c index e173204ae7d7..41db10f9be49 100644 --- a/drivers/net/wireguard/selftest/allowedips.c +++ b/drivers/net/wireguard/selftest/allowedips.c @@ -593,10 +593,10 @@ bool __init wg_allowedips_selftest(void) wg_allowedips_remove_by_peer(&t, a, &mutex); test_negative(4, a, 192, 168, 0, 1); - /* These will hit the WARN_ON(len >= 128) in free_node if something - * goes wrong. + /* These will hit the WARN_ON(len >= MAX_ALLOWEDIPS_BITS) in free_node + * if something goes wrong. */ - for (i = 0; i < 128; ++i) { + for (i = 0; i < MAX_ALLOWEDIPS_BITS; ++i) { part = cpu_to_be64(~(1LLU << (i % 64))); memset(&ip, 0xff, 16); memcpy((u8 *)&ip + (i < 64) * 8, &part, 8);