Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1948624AbdDYPEa (ORCPT ); Tue, 25 Apr 2017 11:04:30 -0400 Received: from frisell.zx2c4.com ([192.95.5.64]:40029 "EHLO frisell.zx2c4.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1948728AbdDYPEX (ORCPT ); Tue, 25 Apr 2017 11:04:23 -0400 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 v4 1/5] skbuff: return -EMSGSIZE in skb_to_sgvec to prevent overflow Date: Tue, 25 Apr 2017 17:04:19 +0200 Message-Id: <20170425150419.2060-1-Jason@zx2c4.com> X-Mailer: git-send-email 2.12.2 In-Reply-To: <20170425.104731.631398016575024152.davem@davemloft.net> References: <20170425.104731.631398016575024152.davem@davemloft.net> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1911 Lines: 56 This is a defense-in-depth measure in response to bugs like 4d6fa57b4dab ("macsec: avoid heap overflow in skb_to_sgvec") Signed-off-by: Jason A. Donenfeld --- v4 fixes the commit message and moves the check into the inner-most if. net/core/skbuff.c | 12 +++++++++++- 1 file changed, 11 insertions(+), 1 deletion(-) diff --git a/net/core/skbuff.c b/net/core/skbuff.c index f86bf69cfb8d..e75640006d78 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) @@ -3517,6 +3519,8 @@ __skb_to_sgvec(struct sk_buff *skb, struct scatterlist *sg, int offset, int len) end = start + skb_frag_size(&skb_shinfo(skb)->frags[i]); if ((copy = end - offset) > 0) { skb_frag_t *frag = &skb_shinfo(skb)->frags[i]; + if (elt && sg_is_last(&sg[elt - 1])) + return -EMSGSIZE; if (copy > len) copy = len; @@ -3537,6 +3541,9 @@ __skb_to_sgvec(struct sk_buff *skb, struct scatterlist *sg, int offset, int len) end = start + frag_iter->len; if ((copy = end - offset) > 0) { + if (elt && sg_is_last(&sg[elt - 1])) + return -EMSGSIZE; + if (copy > len) copy = len; elt += __skb_to_sgvec(frag_iter, sg+elt, offset - start, @@ -3581,6 +3588,9 @@ 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; -- 2.12.2