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[78.154.15.182]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-4954a2e83ddsm256560825e9.10.2026.07.20.02.26.05 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 20 Jul 2026 02:26:06 -0700 (PDT) Message-ID: <27d8e26e-3498-4741-949a-742d057bbcde@blackwall.org> Date: Mon, 20 Jul 2026 12:26:05 +0300 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH net-next 4/5] bridge: Linearize skb once the ND message type is validated Content-Language: en-US, bg To: Danielle Ratson , netdev@vger.kernel.org Cc: dsahern@kernel.org, idosch@nvidia.com, davem@davemloft.net, edumazet@google.com, kuba@kernel.org, pabeni@redhat.com, horms@kernel.org, ja@ssi.bg, petrm@nvidia.com, fw@strlen.de, kuniyu@google.com, bridge@lists.linux.dev, linux-kernel@vger.kernel.org References: From: Nikolay Aleksandrov In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 19/07/2026 16:34, Danielle Ratson wrote: > br_nd_send() parses ND options from ns->opt[] and therefore needs the skb > to be linear. Commit a01aee7cafc5 ("bridge: br_nd_send: linearize skb > before parsing ND options") ensured that by linearizing inside > br_nd_send() itself. > > Move the linearization up into br_is_nd_neigh_msg(), right after > ndisc_check_ns_na() has validated the message as an NS/NA. This makes a > linear buffer a property of every recognized ND message, so that this and > any future ND message handling operate on a linear skb and cannot > reintroduce that class of bug by forgetting to linearize. > > Since the skb is now linear by the time br_nd_send() runs, drop the > linearization there and derive ns from the transport header set by > ndisc_check_ns_na(), instead of recomputing it from the network header. > > If linearization fails under memory pressure, br_is_nd_neigh_msg() returns > NULL and the packet falls back to normal forwarding rather than being > suppressed. > > Reviewed-by: Petr Machata > Signed-off-by: Danielle Ratson > --- > net/bridge/br_arp_nd_proxy.c | 8 +++++--- > 1 file changed, 5 insertions(+), 3 deletions(-) > > diff --git a/net/bridge/br_arp_nd_proxy.c b/net/bridge/br_arp_nd_proxy.c > index 445c930ed59b..46779d9fad61 100644 > --- a/net/bridge/br_arp_nd_proxy.c > +++ b/net/bridge/br_arp_nd_proxy.c > @@ -240,6 +240,9 @@ struct nd_msg *br_is_nd_neigh_msg(struct sk_buff *skb) > if (ndisc_check_ns_na(skb)) > return NULL; > > + if (skb_linearize(skb)) > + return NULL; > + > return (struct nd_msg *)skb_transport_header(skb); > } This one is a bit weird - I wouldn't expect the check and validation to also linearize the skb. I'd rename this helper to show that it also linearizes the skb. Other than that the patch looks good. > > @@ -259,7 +262,7 @@ static void br_nd_send(struct net_bridge *br, struct net_bridge_port *p, > bool dad; > u16 pvid; > > - if (!dev || skb_linearize(request)) > + if (!dev) > return; > > len = LL_RESERVED_SPACE(dev) + sizeof(struct ipv6hdr) + > @@ -276,8 +279,7 @@ static void br_nd_send(struct net_bridge *br, struct net_bridge_port *p, > skb_set_mac_header(reply, 0); > > daddr = eth_hdr(request)->h_source; > - ns = (struct nd_msg *)(skb_network_header(request) + > - sizeof(struct ipv6hdr)); > + ns = (struct nd_msg *)skb_transport_header(request); > > /* Do we need option processing ? */ > ns_olen = request->len - (skb_network_offset(request) +