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Thu, 11 Jun 2026 01:09:05 -0700 (PDT) Received: from u2404-VMware-Virtual-Platform.localdomain ([2a12:a304:100::109f]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-2c1664ad138sm277591035ad.82.2026.06.11.01.08.57 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 11 Jun 2026 01:09:05 -0700 (PDT) From: Sun Jian To: bpf@vger.kernel.org Cc: netdev@vger.kernel.org, linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org, ast@kernel.org, daniel@iogearbox.net, andrii@kernel.org, martin.lau@linux.dev, davem@davemloft.net, kuba@kernel.org, hawk@kernel.org, john.fastabend@gmail.com, sdf@fomichev.me, shuah@kernel.org, jiayuan.chen@linux.dev, toke@redhat.com, menglong.dong@linux.dev, emil@etsalapatis.com, Sun Jian Subject: [PATCH bpf v4 0/2] bpf: Fix generic devmap egress skb sharing Date: Thu, 11 Jun 2026 16:08:47 +0800 Message-ID: <20260611080850.536996-1-sun.jian.kdev@gmail.com> X-Mailer: git-send-email 2.43.0 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=UTF-8 Content-Transfer-Encoding: 8bit Generic XDP devmap multi redirect can leave cloned skbs sharing packet data. When a devmap egress program mutates packet data, another destination sharing the same data may observe that mutation. Fix this by making cloned skbs private before running the generic devmap egress program. Add selftest coverage for the last-destination case, where the final destination runs on the original skb while earlier destinations use cloned skbs. --- v4: * Preserve mac_len after skb_copy(). * Separate errno return from XDP action output in dev_map_bpf_prog_run_skb(). * Zero-initialize net_config in the new selftest. v3: https://lore.kernel.org/bpf/20260611043317.512843-1-sun.jian.kdev@gmail.com/T/#m77fde65437b0398cb470649d4f1feeb85bc134bc * Split the kernel fix and selftest into separate patches. * Move the private-copy logic into dev_map_bpf_prog_run_skb(). * Use deterministic DEVMAP_HASH keys in the last-destination selftest. * Fix the Fixes tag. v2: https://lore.kernel.org/bpf/08c35c70-a59e-4e0e-91db-22b5ec30b611@linux.dev/T/#m613671b243e8651c47f84bb329f0ea668974c549 * Move the private-copy step into dev_map_generic_redirect() so the last-destination path is covered as well. * Use skb_copy() instead of skb_unshare() to keep caller ownership unchanged on allocation failure. * Add a generic XDP last-destination selftest case. v1: https://lore.kernel.org/bpf/CABFUUZFimdrZdq=NWi+N-0sJZWvMwY=f4iF6-3TVMS8=m07Zmw@mail.gmail.com/ Sun Jian (2): bpf: Run generic devmap egress prog on private skb selftests/bpf: Cover generic devmap egress last-dst rewrite kernel/bpf/devmap.c | 41 +++-- .../selftests/bpf/prog_tests/test_xdp_veth.c | 152 +++++++++++++++++- 2 files changed, 180 insertions(+), 13 deletions(-) base-commit: e7ae89a0c97ce2b68b0983cd01eda67cf373517d -- 2.43.0