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Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , linux-kernel@vger.kernel.org Subject: [PATCH bpf-next v4 4/6] bpf: allow new DECAP flags and add guard rails Date: Thu, 16 Apr 2026 08:55:12 +0100 Message-Id: <20260416075514.927101-5-nhudson@akamai.com> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20260416075514.927101-1-nhudson@akamai.com> References: <20260416075514.927101-1-nhudson@akamai.com> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1143,Hydra:6.1.51,FMLib:17.12.100.49 definitions=2026-04-16_02,2026-04-13_04,2025-10-01_01 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 bulkscore=0 malwarescore=0 mlxscore=0 lowpriorityscore=0 phishscore=0 suspectscore=0 mlxlogscore=999 spamscore=0 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.19.0-2604070000 definitions=main-2604160071 X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwNDE2MDA3MyBTYWx0ZWRfX+3ND2MNlLY39 lRUDFMKJ4mX52swDJVn+wYDebmsonkBiHO6ybgp3lDwFrlDE5Pp4PvD9+Z8xzIRk8NeWcPO0AvH kR/11zC8db73ZXf2ElX/nN1odlaUE5JQ3DnrsN0Kc7KOIihua/0G9ZhusH0wUc/zh9tnqFjV7s6 WV5VyXzA0JVlI3DDWCixWZdlKcmDLhtWi2E9b038S20gqoFFg3z8l3XP7Z3HKYUVuSt3yGD9lXn je+VkOBnfOtJvMNXg7fgmUtEzXX3PG8whHFL2t6KQB2eYfVgd4dUnghr8uLs81QIiMhJP18cUuE F/V76vFtV+B55uFVDbRS5OrGUys3mmTHDkLCi01k2oyV7qpIH77/YiX0gn7q464bsG2YhjpQ17O g5bEj4BzwgINi8Y0waOd9V9tArQFCnsayt/1lmM0QNKKLuqGerqNpjwnhS1x+TqPMV4FNdQ7slr im9JQWf6cA/OboQlFGQ== X-Authority-Analysis: v=2.4 cv=f8V4wuyM c=1 sm=1 tr=0 ts=69e095ee cx=c_pps a=StLZT/nZ0R8Xs+spdojYmg==:117 a=StLZT/nZ0R8Xs+spdojYmg==:17 a=A5OVakUREuEA:10 a=VkNPw1HP01LnGYTKEx00:22 a=Ifg-1AOnLHOf1gn6spyb:22 a=KDzEjHMMTas96-nIEKpj:22 a=X7Ea-ya5AAAA:8 a=Hfnf2daL9bryszF4jIsA:9 X-Proofpoint-ORIG-GUID: Lgb7uz9gHO8B9URtoWzZc71mvuuSNcwb X-Proofpoint-GUID: Lgb7uz9gHO8B9URtoWzZc71mvuuSNcwb X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1143,Hydra:6.1.51,FMLib:17.12.100.49 definitions=2026-04-16_02,2026-04-13_04,2025-10-01_01 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 priorityscore=1501 malwarescore=0 impostorscore=0 phishscore=0 lowpriorityscore=0 spamscore=0 adultscore=0 clxscore=1015 suspectscore=0 bulkscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2604070000 definitions=main-2604160073 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 | 44 +++++++++++++++++++++++++++++++++++++++++++- 1 file changed, 43 insertions(+), 1 deletion(-) diff --git a/net/core/filter.c b/net/core/filter.c index 4e860da4381d..7f8d43420afb 100644 --- a/net/core/filter.c +++ b/net/core/filter.c @@ -56,6 +56,7 @@ #include #include #include +#include #include #include #include @@ -3490,6 +3491,12 @@ static u32 bpf_skb_net_base_len(const struct sk_buff *skb) #define BPF_F_ADJ_ROOM_DECAP_L3_MASK (BPF_F_ADJ_ROOM_DECAP_L3_IPV4 | \ BPF_F_ADJ_ROOM_DECAP_L3_IPV6) +#define BPF_F_ADJ_ROOM_DECAP_L4_MASK (BPF_F_ADJ_ROOM_DECAP_L4_UDP | \ + BPF_F_ADJ_ROOM_DECAP_L4_GRE) + +#define BPF_F_ADJ_ROOM_DECAP_IPXIP_MASK (BPF_F_ADJ_ROOM_DECAP_IPXIP4 | \ + BPF_F_ADJ_ROOM_DECAP_IPXIP6) + #define BPF_F_ADJ_ROOM_ENCAP_MASK (BPF_F_ADJ_ROOM_ENCAP_L3_MASK | \ BPF_F_ADJ_ROOM_ENCAP_L4_GRE | \ BPF_F_ADJ_ROOM_ENCAP_L4_UDP | \ @@ -3497,7 +3504,9 @@ 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 | \ @@ -3740,6 +3749,8 @@ BPF_CALL_4(bpf_skb_adjust_room, struct sk_buff *, skb, s32, len_diff, } if (flags & BPF_F_ADJ_ROOM_DECAP_MASK) { + u32 len_decap_min = 0; + if (!shrink) return -EINVAL; @@ -3748,6 +3759,37 @@ BPF_CALL_4(bpf_skb_adjust_room, struct sk_buff *, skb, s32, len_diff, 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_MASK) + len_decap_min += bpf_skb_net_base_len(skb); + + 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 (flags & BPF_F_ADJ_ROOM_DECAP_IPXIP4) + len_decap_min += sizeof(struct iphdr); + + if (flags & BPF_F_ADJ_ROOM_DECAP_IPXIP6) + len_decap_min += sizeof(struct ipv6hdr); + + if (len_diff_abs < len_decap_min) + return -EINVAL; + if (flags & BPF_F_ADJ_ROOM_DECAP_L3_IPV4) len_min = sizeof(struct iphdr); -- 2.34.1