From mboxrd@z Thu Jan 1 00:00:00 1970 From: Pablo Neira Ayuso Subject: Re: [PATCH 1/3] netfilter: Fix copy_to_user too small size parametre. Date: Thu, 1 Mar 2012 11:18:09 +0100 Message-ID: <20120301101809.GA6488@1984> References: <1330593390-19233-1-git-send-email-santoshprasadnayak@gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: bart.de.schuymer@pandora.be, kaber@trash.net, shemminger@vyatta.com, davem@davemloft.net, netfilter-devel@vger.kernel.org, netfilter@vger.kernel.org, coreteam@netfilter.org, bridge@lists.linux-foundation.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, kernel-janitors@vger.kernel.org To: santosh nayak Return-path: Received: from mail.us.es ([193.147.175.20]:33263 "EHLO mail.us.es" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S966042Ab2CAKSW (ORCPT ); Thu, 1 Mar 2012 05:18:22 -0500 Content-Disposition: inline In-Reply-To: <1330593390-19233-1-git-send-email-santoshprasadnayak@gmail.com> Sender: netfilter-devel-owner@vger.kernel.org List-ID: On Thu, Mar 01, 2012 at 02:46:30PM +0530, santosh nayak wrote: > From: Santosh Nayak > > While copying to userspace, the size of source is 29byte where as > size parametre is 32 byte. Its leaking extra-information from > kernel space to user space. > Replace EBT_FUNCTION_MAXNAMELEN by XT_EXTENSION_MAXNAMELEN. There's no information leak. Let me clarify this. Have a look at /linux/netfilter/x_tables.h, then you find: #define XT_FUNCTION_MAXNAMELEN 30 #define XT_EXTENSION_MAXNAMELEN 29 #define XT_TABLE_MAXNAMELEN 32 For iptables, everything has been 30 bytes, but we stole one byte to store the revision field for matches/targets. For ebtables, there's no revision field and the length of the table name is different. But linux/netfilter/in ebtables.h, you'll find: #define EBT_TABLE_MAXNAMELEN 32 #define EBT_CHAIN_MAXNAMELEN EBT_TABLE_MAXNAMELEN #define EBT_FUNCTION_MAXNAMELEN EBT_TABLE_MAXNAMELEN Note that someone decided to use 32 bytes for the ebtables tables/match/target name instead of 30 bytes in iptables. Yes, it sucks a bit we have to live with these interfaces until we have some netlink interface for all these things. > Signed-off-by: Santosh Nayak > --- > net/bridge/netfilter/ebtables.c | 6 +++--- > 1 files changed, 3 insertions(+), 3 deletions(-) > > diff --git a/net/bridge/netfilter/ebtables.c b/net/bridge/netfilter/ebtables.c > index 5864cc4..f3fcbd9 100644 > --- a/net/bridge/netfilter/ebtables.c > +++ b/net/bridge/netfilter/ebtables.c > @@ -1335,7 +1335,7 @@ static inline int ebt_make_matchname(const struct ebt_entry_match *m, > const char *base, char __user *ubase) > { > char __user *hlp = ubase + ((char *)m - base); > - if (copy_to_user(hlp, m->u.match->name, EBT_FUNCTION_MAXNAMELEN)) > + if (copy_to_user(hlp, m->u.match->name, XT_EXTENSION_MAXNAMELEN)) > return -EFAULT; > return 0; > } > @@ -1344,7 +1344,7 @@ static inline int ebt_make_watchername(const struct ebt_entry_watcher *w, > const char *base, char __user *ubase) > { > char __user *hlp = ubase + ((char *)w - base); > - if (copy_to_user(hlp , w->u.watcher->name, EBT_FUNCTION_MAXNAMELEN)) > + if (copy_to_user(hlp , w->u.watcher->name, XT_EXTENSION_MAXNAMELEN)) > return -EFAULT; > return 0; > } > @@ -1368,7 +1368,7 @@ ebt_make_names(struct ebt_entry *e, const char *base, char __user *ubase) > ret = EBT_WATCHER_ITERATE(e, ebt_make_watchername, base, ubase); > if (ret != 0) > return ret; > - if (copy_to_user(hlp, t->u.target->name, EBT_FUNCTION_MAXNAMELEN)) > + if (copy_to_user(hlp, t->u.target->name, XT_EXTENSION_MAXNAMELEN)) > return -EFAULT; > return 0; > } > -- > 1.7.4.4 > > -- > To unsubscribe from this list: send the line "unsubscribe netdev" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html