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Mon, 03 Aug 2026 08:25:22 -0700 (PDT) Date: Mon, 3 Aug 2026 18:25:21 +0300 From: Nikolay Aleksandrov To: Danielle Ratson Cc: netdev@vger.kernel.org, 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 Subject: Re: [PATCH net-next v2 4/5] bridge: Linearize skb once the ND message type is validated Message-ID: References: <20260803112505.613873-1-danieller@nvidia.com> <20260803112505.613873-5-danieller@nvidia.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260803112505.613873-5-danieller@nvidia.com> On Mon, Aug 03, 2026 at 02:25:04PM +0300, 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 > --- > > Notes: > v2: > * Add a comment noting that br_is_nd_neigh_msg() also linearizes the > skb. > > net/bridge/br_arp_nd_proxy.c | 11 ++++++++--- > 1 file changed, 8 insertions(+), 3 deletions(-) > > diff --git a/net/bridge/br_arp_nd_proxy.c b/net/bridge/br_arp_nd_proxy.c > index 445c930ed59b..6b6de0eff38c 100644 > --- a/net/bridge/br_arp_nd_proxy.c > +++ b/net/bridge/br_arp_nd_proxy.c > @@ -235,11 +235,17 @@ void br_do_proxy_suppress_arp(struct sk_buff *skb, struct net_bridge *br, > #endif > > #if IS_ENABLED(CONFIG_IPV6) > +/* Validate skb as an NS/NA and linearize it for br_nd_send()'s ND > + * option parsing; returns the nd_msg, or NULL on failure. > + */ > 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); > } > > @@ -259,7 +265,7 @@ 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 +282,7 @@ 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) + > -- > 2.54.0 > Thanks, Acked-by: Nikolay Aleksandrov