Return-path: Received: from ebb05.tieto.com ([131.207.168.36]:61036 "EHLO ebb05.tieto.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751849Ab3BGKQE (ORCPT ); Thu, 7 Feb 2013 05:16:04 -0500 From: Szymon Janc To: Dan Carpenter CC: Lauro Ramos Venancio , Aloisio Almeida Jr , Samuel Ortiz , "David S. Miller" , "John W. Linville" , Thierry Escande , "linux-wireless@vger.kernel.org" , "linux-nfc@ml01.01.org" , "netdev@vger.kernel.org" , "kernel-janitors@vger.kernel.org" Subject: Re: [patch] NFC: llcp: integer underflow in nfc_llcp_set_remote_gb() Date: Thu, 7 Feb 2013 11:16:01 +0100 Message-ID: <2148581.S8tzak9aE2@uw000953> (sfid-20130207_111610_550255_93DFD712) In-Reply-To: <20130131081645.GA14812@elgon.mountain> References: <20130131081645.GA14812@elgon.mountain> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Sender: linux-wireless-owner@vger.kernel.org List-ID: Hi Dan, On Thursday 31 of January 2013 10:16:46 Dan Carpenter wrote: > If gb_len is less than 3 it would cause an integer underflow and > possibly memory corruption in nfc_llcp_parse_gb_tlv(). > > I removed the old test for gb_len == 0. I also removed the test for > ->remote_gb == NULL. It's not possible for ->remote_gb to be NULL and > we have already dereferenced ->remote_gb_len so it's too late to test. > > The old test return -ENODEV but my test returns -EINVAL. > > Signed-off-by: Dan Carpenter > > diff --git a/net/nfc/llcp/llcp.c b/net/nfc/llcp/llcp.c > index 85bc75c..746f5a2 100644 > --- a/net/nfc/llcp/llcp.c > +++ b/net/nfc/llcp/llcp.c > @@ -549,14 +549,13 @@ int nfc_llcp_set_remote_gb(struct nfc_dev *dev, u8 *gb, u8 gb_len) > pr_err("No LLCP device\n"); > return -ENODEV; > } > + if (gb_len < 3) > + return -EINVAL; Maybe define NFC_MIN_GT_LEN and test it together with NFC_MAX_GT_LEN in nfc_set_remote_general_bytes() ? > > memset(local->remote_gb, 0, NFC_MAX_GT_LEN); > memcpy(local->remote_gb, gb, gb_len); > local->remote_gb_len = gb_len; > > - if (local->remote_gb == NULL || local->remote_gb_len == 0) > - return -ENODEV; > - > if (memcmp(local->remote_gb, llcp_magic, 3)) { > pr_err("MAC does not support LLCP\n"); > return -EINVAL; -- BR Szymon Janc