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[34.85.134.180]) by smtp.gmail.com with UTF8SMTPSA id 00721157ae682-79a1688ca84sm78216867b3.48.2026.03.17.06.30.20 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 17 Mar 2026 06:30:20 -0700 (PDT) Date: Tue, 17 Mar 2026 09:30:20 -0400 From: Willem de Bruijn To: Nick Hudson , bpf@vger.kernel.org Cc: Willem de Bruijn , Nick Hudson , Max Tottenham , Anna Glasgall , Alexei Starovoitov , Daniel Borkmann , Andrii Nakryiko , Martin KaFai Lau , "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , netdev@vger.kernel.org, linux-kernel@vger.kernel.org Message-ID: In-Reply-To: <20260317121429.2399539-5-nhudson@akamai.com> References: <20260317121429.2399539-1-nhudson@akamai.com> <20260317121429.2399539-5-nhudson@akamai.com> Subject: Re: [PATCH v1 4/5] bpf: add guard rails for new DECAP flags Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Nick Hudson wrote: > Add checks to require shrink-only decap, reject conflicting decap flag combinations, and verify removed length is sufficient for claimed header decapsulation. > > Co-developed-by: Max Tottenham > Signed-off-by: Max Tottenham > Co-developed-by: Anna Glasgall > Signed-off-by: Anna Glasgall > Signed-off-by: Nick Hudson This patch probably should come before 3, as 3 enables the features without the guard rails in place. > --- > net/core/filter.c | 45 ++++++++++++++++++++++++++++++++++++--------- > 1 file changed, 36 insertions(+), 9 deletions(-) > > diff --git a/net/core/filter.c b/net/core/filter.c > index ac7e1068fe4c..437e0da34f84 100644 > --- a/net/core/filter.c > +++ b/net/core/filter.c > @@ -56,6 +56,7 @@ > #include > #include > #include > +#include > #include > #include > #include > @@ -3745,20 +3746,46 @@ BPF_CALL_4(bpf_skb_adjust_room, struct sk_buff *, skb, s32, len_diff, > return -ENOTSUPP; > } > > - if (flags & BPF_F_ADJ_ROOM_DECAP_L3_MASK) { > + if (flags & BPF_F_ADJ_ROOM_DECAP_MASK) { > + u32 len_decap_min = 0; > + > if (!shrink) > return -EINVAL; > > - switch (flags & BPF_F_ADJ_ROOM_DECAP_L3_MASK) { > - case BPF_F_ADJ_ROOM_DECAP_L3_IPV4: > + if ((flags & BPF_F_ADJ_ROOM_DECAP_L3_MASK) == > + BPF_F_ADJ_ROOM_DECAP_L3_MASK) > + return -EINVAL; > + > + if ((flags & BPF_F_ADJ_ROOM_DECAP_L4_MASK) == > + BPF_F_ADJ_ROOM_DECAP_L4_MASK) > + return -EINVAL; > + > + if ((flags & BPF_F_ADJ_ROOM_DECAP_IPXIP_MASK) == > + BPF_F_ADJ_ROOM_DECAP_IPXIP_MASK) > + return -EINVAL; > + Are these equality tests shorthand based on knowledge that each only have two options, so equality implies more than one option set? That is not obvious/self documenting. Please add a brief comment. > + if ((flags & BPF_F_ADJ_ROOM_DECAP_L4_MASK) && > + (flags & BPF_F_ADJ_ROOM_DECAP_IPXIP_MASK)) > + return -EINVAL; > + > + if (mode == BPF_ADJ_ROOM_MAC) > + len_decap_min += proto == htons(ETH_P_IP) ? > + sizeof(struct iphdr) : sizeof(struct ipv6hdr); MAC is not a GSO related decap, can be used for insertion/deletion of L2.5 headers. This should be dropped. > + > + if (flags & BPF_F_ADJ_ROOM_DECAP_L4_UDP) > + len_decap_min += sizeof(struct udphdr); > + > + if (flags & BPF_F_ADJ_ROOM_DECAP_L4_GRE) > + len_decap_min += sizeof(struct gre_base_hdr); > + > + if (len_diff_abs < len_decap_min) > + return -EINVAL; > + > + if (flags & BPF_F_ADJ_ROOM_DECAP_L3_IPV4) > len_min = sizeof(struct iphdr); > - break; > - case BPF_F_ADJ_ROOM_DECAP_L3_IPV6: > + > + if (flags & BPF_F_ADJ_ROOM_DECAP_L3_IPV6) > len_min = sizeof(struct ipv6hdr); > - break; > - default: > - return -EINVAL; > - } > } > > len_cur = skb->len - skb_network_offset(skb); > -- > 2.34.1 >