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: 9698291 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork.web.codeaurora.org (Postfix) with ESMTP id 8997160224 for ; Tue, 25 Apr 2017 14:21:31 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 60C152522B for ; Tue, 25 Apr 2017 14:21:31 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 5597D2857D; Tue, 25 Apr 2017 14:21:31 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-4.1 required=2.0 tests=BAYES_00,DKIM_SIGNED, RCVD_IN_DNSWL_MED,T_DKIM_INVALID autolearn=ham version=3.3.1 Received: from mother.openwall.net (mother.openwall.net [195.42.179.200]) by mail.wl.linuxfoundation.org (Postfix) with SMTP id 91FDA2522B for ; Tue, 25 Apr 2017 14:21:30 +0000 (UTC) Received: (qmail 11812 invoked by uid 550); 25 Apr 2017 14:21:28 -0000 Mailing-List: contact kernel-hardening-help@lists.openwall.com; run by ezmlm Precedence: bulk List-Post: List-Help: List-Unsubscribe: List-Subscribe: List-ID: Delivered-To: mailing list kernel-hardening@lists.openwall.com Received: (qmail 11794 invoked from network); 25 Apr 2017 14:21:28 -0000 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== 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" 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> Subject: [kernel-hardening] [PATCH v3 1/5] skbuff: return -EMSGSIZE in skb_to_sgvec to prevent overflow X-Virus-Scanned: ClamAV using ClamSMTP 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;