From patchwork Tue Apr 25 14:21:12 2017 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Jason A. Donenfeld" X-Patchwork-Id: 754851 X-Patchwork-Delegate: davem@davemloft.net Return-Path: X-Original-To: patchwork-incoming@ozlabs.org Delivered-To: patchwork-incoming@ozlabs.org Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by ozlabs.org (Postfix) with ESMTP id 3wC54J3QTbz9s8S for ; Wed, 26 Apr 2017 00:21:36 +1000 (AEST) Authentication-Results: ozlabs.org; dkim=pass (2048-bit key; unprotected) header.d=zx2c4.com header.i=@zx2c4.com header.b="wzkbivGO"; dkim-atps=neutral Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1947881AbdDYOVU (ORCPT ); Tue, 25 Apr 2017 10:21:20 -0400 Received: from frisell.zx2c4.com ([192.95.5.64]:50103 "EHLO frisell.zx2c4.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1947870AbdDYOVR (ORCPT ); Tue, 25 Apr 2017 10:21:17 -0400 Received: by frisell.zx2c4.com (ZX2C4 Mail Server) with ESMTP id 5f661df9; Tue, 25 Apr 2017 14:12:36 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha1; c=relaxed; d=zx2c4.com; h=from:to:cc :subject:date:message-id:in-reply-to:references; s=mail; bh=tOtz e5pcO+n4w6iuok8qlvMDPGg=; b=wzkbivGOK+CZN//+9H82oVAy359/+vPMPUxD XPGWcOyN1XZP0xeV9ubeuVK0tgNFGnkI/gAGuv35mkwJiGjNguuDmXRbZJuSUcFB XnxgP1tr+d8ymutuLIO8CCp5Gplmp1lW3ee3MkrUp0DAyTV99imluKfmRp/Xbhbk u0OZTLBno+4GNFfaNQOY9bIxIGOspoynYCe3zNfXxavr1NkJ4CLZOPfaF+nuVXo7 M6dQb+YBGc8xckwZ6pxyV2G5NxGNpou8qGN4DFXW1U5+eQmQTgjffAyZVuNh1g59 aED99Cack6Aws6AVBOwGn3rvIZGrqkI57EREnuA8toqqFTFVRQ== Received: by frisell.zx2c4.com (ZX2C4 Mail Server) with ESMTPSA id 53cf045d (TLSv1.2:ECDHE-RSA-AES256-GCM-SHA384:256:NO); Tue, 25 Apr 2017 14:12:36 +0000 (UTC) From: "Jason A. Donenfeld" To: netdev@vger.kernel.org, linux-kernel@vger.kernel.org, davem@davemloft.net, David.Laight@aculab.com, kernel-hardening@lists.openwall.com Cc: "Jason A. Donenfeld" Subject: [PATCH v3 1/5] skbuff: return -EMSGSIZE in skb_to_sgvec to prevent overflow Date: Tue, 25 Apr 2017 16:21:12 +0200 Message-Id: <20170425142112.29702-1-Jason@zx2c4.com> X-Mailer: git-send-email 2.12.2 In-Reply-To: <20170425141609.28459-1-Jason@zx2c4.com> References: <20170425141609.28459-1-Jason@zx2c4.com> Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org This is a defense-in-depth measure in response to bugs like 4d6fa57b4dab0d77f4d8e9d9c73d1e63f6fe8fee. Signed-off-by: Jason A. Donenfeld --- Sorry for the completely stupid amount of churn - v1,v2,v3 in the span of two minutes. It's just that after noticing first that nsg needs to be checked, I also noticed something a bit worse: that there was a bug (exploitable?) where if skb_to_sgvec was called with empty values, there would be an out-of-bounds write into sg[0 - 1]. So, this third (and hopefully final!) patch fixes that bug while we're at it. net/core/skbuff.c | 13 ++++++++++++- 1 file changed, 12 insertions(+), 1 deletion(-) diff --git a/net/core/skbuff.c b/net/core/skbuff.c index f86bf69cfb8d..d103134deddb 100644 --- a/net/core/skbuff.c +++ b/net/core/skbuff.c @@ -3489,7 +3489,9 @@ void __init skb_init(void) * @len: Length of buffer space to be mapped * * Fill the specified scatter-gather list with mappings/pointers into a - * region of the buffer space attached to a socket buffer. + * region of the buffer space attached to a socket buffer. Returns either + * the number of scatterlist items used, or -EMSGSIZE if the contents + * could not fit. */ static int __skb_to_sgvec(struct sk_buff *skb, struct scatterlist *sg, int offset, int len) @@ -3512,6 +3514,9 @@ __skb_to_sgvec(struct sk_buff *skb, struct scatterlist *sg, int offset, int len) for (i = 0; i < skb_shinfo(skb)->nr_frags; i++) { int end; + if (elt && sg_is_last(&sg[elt - 1])) + return -EMSGSIZE; + WARN_ON(start > offset + len); end = start + skb_frag_size(&skb_shinfo(skb)->frags[i]); @@ -3535,6 +3540,9 @@ __skb_to_sgvec(struct sk_buff *skb, struct scatterlist *sg, int offset, int len) WARN_ON(start > offset + len); + if (elt && sg_is_last(&sg[elt - 1])) + return -EMSGSIZE; + end = start + frag_iter->len; if ((copy = end - offset) > 0) { if (copy > len) @@ -3581,6 +3589,9 @@ int skb_to_sgvec(struct sk_buff *skb, struct scatterlist *sg, int offset, int le { int nsg = __skb_to_sgvec(skb, sg, offset, len); + if (nsg <= 0) + return nsg; + sg_mark_end(&sg[nsg - 1]); return nsg;