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[34.85.235.172]) by smtp.gmail.com with ESMTPSA id 956f58d0204a3-65bff4fb88esm695402d50.5.2026.04.28.19.47.09 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 28 Apr 2026 19:47:09 -0700 (PDT) Date: Tue, 28 Apr 2026 22:47:08 -0400 From: Willem de Bruijn To: Jakub Kicinski , davem@davemloft.net Cc: netdev@vger.kernel.org, edumazet@google.com, pabeni@redhat.com, andrew+netdev@lunn.ch, horms@kernel.org, willemdebruijn.kernel@gmail.com, daniel.zahka@gmail.com, Jakub Kicinski Message-ID: In-Reply-To: <20260428205352.1247325-2-kuba@kernel.org> References: <20260428205352.1247325-1-kuba@kernel.org> <20260428205352.1247325-2-kuba@kernel.org> Subject: Re: [PATCH net-next 1/3] psp: validate protocol before mutating skb in psp_dev_encapsulate() Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Jakub Kicinski wrote: > Code checkers / AI scans will complain that we have already modified > the packet by the time we realize that protocol is not IP. > > Move the skb->protocol check to before skb_push()/memmove() so that > the skb is not left in a corrupted state when the function returns > false for an unsupported protocol. psp_dev_rcv() follows similar > pattern. > > Today this path is unreachable because both in-tree callers (mlx5 and > netdevsim) only reach psp_dev_encapsulate() from TCP socket TX paths > where skb->protocol is always ETH_P_IP or ETH_P_IPV6, and both drop > the skb on a false return, anyway. > > Signed-off-by: Jakub Kicinski Reviewed-by: Willem de Bruijn > --- > net/psp/psp_main.c | 8 +++++--- > 1 file changed, 5 insertions(+), 3 deletions(-) > > diff --git a/net/psp/psp_main.c b/net/psp/psp_main.c > index 9508b6c38003..652ec8a9c8a4 100644 > --- a/net/psp/psp_main.c > +++ b/net/psp/psp_main.c > @@ -228,6 +228,10 @@ bool psp_dev_encapsulate(struct net *net, struct sk_buff *skb, __be32 spi, > u32 ethr_len = skb_mac_header_len(skb); > u32 bufflen = ethr_len + network_len; > > + if (skb->protocol != htons(ETH_P_IP) && > + skb->protocol != htons(ETH_P_IPV6)) > + return false; > + > if (skb_cow_head(skb, PSP_ENCAP_HLEN)) > return false; > > @@ -243,11 +247,9 @@ bool psp_dev_encapsulate(struct net *net, struct sk_buff *skb, __be32 spi, > ip_hdr(skb)->check = 0; > ip_hdr(skb)->check = > ip_fast_csum((u8 *)ip_hdr(skb), ip_hdr(skb)->ihl); > - } else if (skb->protocol == htons(ETH_P_IPV6)) { > + } else { > ipv6_hdr(skb)->nexthdr = IPPROTO_UDP; > be16_add_cpu(&ipv6_hdr(skb)->payload_len, PSP_ENCAP_HLEN); > - } else { > - return false; > } > > skb_set_inner_ipproto(skb, IPPROTO_TCP); > -- > 2.54.0 >