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[73.241.150.58]) by smtp.gmail.com with ESMTPSA id m20sm3835140pgn.62.2020.07.23.12.35.25 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 23 Jul 2020 12:35:25 -0700 (PDT) Subject: Re: [PATCH] netlink: add buffer boundary checking To: Mark Salyzyn , linux-kernel@vger.kernel.org Cc: kernel-team@android.com, netdev@vger.kernel.org, "David S. Miller" , Jakub Kicinski , Thomas Graf References: <20200723182136.2550163-1-salyzyn@android.com> From: Eric Dumazet Message-ID: <09cd1829-8e41-bef5-ba5e-1c446c166778@gmail.com> Date: Thu, 23 Jul 2020 12:35:24 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.9.0 MIME-Version: 1.0 In-Reply-To: <20200723182136.2550163-1-salyzyn@android.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 7/23/20 11:21 AM, Mark Salyzyn wrote: > Many of the nla_get_* inlines fail to check attribute's length before > copying the content resulting in possible out-of-boundary accesses. > Adjust the inlines to perform nla_len checking, for the most part > using the nla_memcpy function to faciliate since these are not > necessarily performance critical and do not need a likely fast path. > > Signed-off-by: Mark Salyzyn > Cc: netdev@vger.kernel.org > Cc: linux-kernel@vger.kernel.org > Cc: kernel-team@android.com > Cc: "David S. Miller" > Cc: Jakub Kicinski > Cc: Thomas Graf > Fixes: bfa83a9e03cf ("[NETLINK]: Type-safe netlink messages/attributes interface") > --- > include/net/netlink.h | 66 +++++++++++++++++++++++++++++++++++-------- > 1 file changed, 54 insertions(+), 12 deletions(-) > > diff --git a/include/net/netlink.h b/include/net/netlink.h > index c0411f14fb53..11c0f153be7c 100644 > --- a/include/net/netlink.h > +++ b/include/net/netlink.h > @@ -1538,7 +1538,11 @@ static inline int nla_put_bitfield32(struct sk_buff *skb, int attrtype, > */ > static inline u32 nla_get_u32(const struct nlattr *nla) > { > - return *(u32 *) nla_data(nla); > + u32 tmp; > + > + nla_memcpy(&tmp, nla, sizeof(tmp)); > + > + return tmp; I believe this will hide bugs, that syzbot was able to catch. Instead, you could perhaps introduce a CONFIG_DEBUG_NETLINK option, and add a WARN_ON_ONCE(nla_len(nla) < sizeof(u32)) so that we can detect bugs in callers.