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[34.85.134.180]) by smtp.gmail.com with UTF8SMTPSA id 956f58d0204a3-64e91be032asm2180679d50.14.2026.03.18.13.02.54 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 18 Mar 2026 13:02:55 -0700 (PDT) Date: Wed, 18 Mar 2026 16:02:54 -0400 From: Willem de Bruijn To: Nick Hudson , bpf@vger.kernel.org, netdev@vger.kernel.org Cc: Willem de Bruijn , Nick Hudson , Max Tottenham , Anna Glasgall , Martin KaFai Lau , Daniel Borkmann , Alexei Starovoitov , Andrii Nakryiko , "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , linux-kernel@vger.kernel.org Message-ID: In-Reply-To: <20260318134242.2725749-5-nhudson@akamai.com> References: <20260318134242.2725749-1-nhudson@akamai.com> <20260318134242.2725749-5-nhudson@akamai.com> Subject: Re: [PATCH v2 4/5] bpf: allow new DECAP flags and add guard rails 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 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 > --- > net/core/filter.c | 47 +++++++++++++++++++++++++++++++++++++---------- > 1 file changed, 37 insertions(+), 10 deletions(-) > > diff --git a/net/core/filter.c b/net/core/filter.c > index 7c2871b40fe4..47aec44a9cd3 100644 > --- a/net/core/filter.c > +++ b/net/core/filter.c > @@ -56,6 +56,7 @@ > #include > #include > #include > +#include > #include > #include > #include > @@ -3496,7 +3497,9 @@ static u32 bpf_skb_net_base_len(const struct sk_buff *skb) > BPF_F_ADJ_ROOM_ENCAP_L2( \ > BPF_ADJ_ROOM_ENCAP_L2_MASK)) > > -#define BPF_F_ADJ_ROOM_DECAP_MASK (BPF_F_ADJ_ROOM_DECAP_L3_MASK) > +#define BPF_F_ADJ_ROOM_DECAP_MASK (BPF_F_ADJ_ROOM_DECAP_L3_MASK | \ > + BPF_F_ADJ_ROOM_DECAP_L4_MASK | \ > + BPF_F_ADJ_ROOM_DECAP_IPXIP_MASK) > > #define BPF_F_ADJ_ROOM_MASK (BPF_F_ADJ_ROOM_FIXED_GSO | \ > BPF_F_ADJ_ROOM_ENCAP_MASK | \ > @@ -3743,20 +3746,44 @@ 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: > + /* Reject mutually exclusive decap flag pairs. */ > + 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; > + > + /* Reject mutually exclusive decap tunnel type flags. */ > + if ((flags & BPF_F_ADJ_ROOM_DECAP_L4_MASK) && > + (flags & BPF_F_ADJ_ROOM_DECAP_IPXIP_MASK)) > + return -EINVAL; > + > + 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; Should this test come after the below IP flags? > + > + 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 >