netdev - Re: [PATCH v2] netlink: don't compare the nul-termination in nla

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Message-Id: <20140401.152606.1113760851598806005.davem@davemloft.net>
Date:	Tue, 01 Apr 2014 15:26:06 -0400 (EDT)
From:	David Miller <davem@...emloft.net>
To:	pablo@...filter.org
Cc:	netdev@...r.kernel.org, fw@...len.de, tgraf@...g.ch
Subject: Re: [PATCH v2] netlink: don't compare the nul-termination in
 nla_strcmp

From: Pablo Neira Ayuso <pablo@...filter.org>
Date: Tue,  1 Apr 2014 19:38:44 +0200

> From: Pablo Neira <pablo@...filter.org>
> 
> nla_strcmp compares the string length plus one, so it's implicitly
> including the nul-termination in the comparison.
> 
>  int nla_strcmp(const struct nlattr *nla, const char *str)
>  {
>         int len = strlen(str) + 1;
>         ...
>                 d = memcmp(nla_data(nla), str, len);
> 
> However, if NLA_STRING is used, userspace can send us a string without
> the nul-termination. This is a problem since the string
> comparison will not match as the last byte may be not the
> nul-termination.
> 
> Fix this by skipping the comparison of the nul-termination if the
> attribute data is nul-terminated. Suggested by Thomas Graf.
> 
> Cc: Florian Westphal <fw@...len.de>
> Cc: Thomas Graf <tgraf@...g.ch>
> Signed-off-by: Pablo Neira Ayuso <pablo@...filter.org>

Applied and queued up for -stable, thanks Pablo.
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