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([2601:647:6700:3390::c8d1]) by smtp.gmail.com with ESMTPSA id d2e1a72fcca58-747afeab743sm8344713b3a.54.2025.06.02.14.33.11 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 02 Jun 2025 14:33:11 -0700 (PDT) From: Kuniyuki Iwashima To: rafalbilkowski@gmail.com Cc: alex.aring@gmail.com, davem@davemloft.net, dsahern@kernel.org, edumazet@google.com, kuba@kernel.org, linux-kernel@vger.kernel.org, netdev@vger.kernel.org, pabeni@redhat.com Subject: Re: [PATCH] ipv6: ndisc: fix potential out-of-bounds read in ndisc_router_discovery() Date: Mon, 2 Jun 2025 14:32:35 -0700 Message-ID: <20250602213310.2519903-1-kuni1840@gmail.com> X-Mailer: git-send-email 2.49.0 In-Reply-To: <20250602065826.168402-1-rafalbilkowski@gmail.com> References: <20250602065826.168402-1-rafalbilkowski@gmail.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: Rafal Bilkowski Date: Mon, 2 Jun 2025 08:58:26 +0200 > This patch adds a length check at the start of ndisc_router_discovery() I think it already has the check. ---8<--- optlen = (skb_tail_pointer(skb) - skb_transport_header(skb)) - sizeof(struct ra_msg); ... if (optlen < 0) return SKB_DROP_REASON_PKT_TOO_SMALL; ---8<--- > to prevent a potential out-of-bounds read if a short packet is received. > Without this check, the function may dereference memory outside the > buffer. Do you have a KMSAM splat ? > > Fixes: 8610c7c6e3bd ("net: ipv6: add support for rpl sr exthdr") > Signed-off-by: Rafal Bilkowski > --- > net/ipv6/ndisc.c | 4 ++++ > 1 file changed, 4 insertions(+) > > diff --git a/net/ipv6/ndisc.c b/net/ipv6/ndisc.c > index 8d853971f2f6..bdaac5a195d6 100644 > --- a/net/ipv6/ndisc.c > +++ b/net/ipv6/ndisc.c > @@ -1235,6 +1235,10 @@ static void ndisc_ra_useropt(struct sk_buff *ra, struct nd_opt_hdr *opt) > > static enum skb_drop_reason ndisc_router_discovery(struct sk_buff *skb) > { > + // Check if the buffer contains enough data for the struct ra_msg > + if (!pskb_may_pull(skb, skb_transport_offset(skb) + sizeof(struct ra_msg))) > + return SKB_DROP_REASON_PKT_TOO_SMALL; Please run checkpatch.pl. We don't add code before variable declarations. Also, the skb is linearized in ndisc_rcv(). > + > struct ra_msg *ra_msg = (struct ra_msg *)skb_transport_header(skb); > bool send_ifinfo_notify = false; > struct neighbour *neigh = NULL; > -- > 2.43.0