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Wed, 03 Jun 2026 07:30:26 -0700 (PDT) Received: from alrua-x1.borgediget.toke.dk ([45.145.92.2]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-490b60f6d5asm68311455e9.0.2026.06.03.07.30.24 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 03 Jun 2026 07:30:24 -0700 (PDT) Received: by alrua-x1.borgediget.toke.dk (Postfix, from userid 1000) id E15C57BAEB7; Wed, 03 Jun 2026 16:30:23 +0200 (CEST) From: Toke =?utf-8?Q?H=C3=B8iland-J=C3=B8rgensen?= To: Ren Wei , netdev@vger.kernel.org, bpf@vger.kernel.org Cc: ast@kernel.org, daniel@iogearbox.net, davem@davemloft.net, kuba@kernel.org, hawk@kernel.org, john.fastabend@gmail.com, sdf@fomichev.me, andrii@kernel.org, martin.lau@linux.dev, eddyz87@gmail.com, memxor@gmail.com, song@kernel.org, yonghong.song@linux.dev, jolsa@kernel.org, liuhangbin@gmail.com, yuantan098@gmail.com, zcliangcn@gmail.com, bird@lzu.edu.cn, zzhan461@ucr.edu, n05ec@lzu.edu.cn Subject: Re: [PATCH bpf v2] bpf: devmap: reject fragmented frames in clone-based broadcasts In-Reply-To: <21c2d153dd25603d359069a02bf06779b51f6423.1780385378.git.zzhan461@ucr.edu> References: <21c2d153dd25603d359069a02bf06779b51f6423.1780385378.git.zzhan461@ucr.edu> X-Clacks-Overhead: GNU Terry Pratchett Date: Wed, 03 Jun 2026 16:30:23 +0200 Message-ID: <87v7bzbssg.fsf@toke.dk> 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: quoted-printable Ren Wei writes: > From: Zhao Zhang > > Devmap broadcast redirects clone the packet for all but the last > destination. > > For native XDP, that clone path copies only the linear xdp_frame data, > while fragmented frames keep skb_shared_info in tailroom outside the > linear area. Cloning such a frame leaves XDP_FLAGS_HAS_FRAGS set but > without valid frag metadata, and the later free path can interpret > uninitialized tail data as skb_shared_info, leading to an out-of-bounds > access during frame return. > > Reject fragmented native XDP frames in dev_map_enqueue_clone(). > > Add the same restriction to the generic XDP clone path in > dev_map_redirect_clone(). Generic XDP represents fragmented packets as > nonlinear skbs, and rejecting them here keeps clone-based broadcast > support aligned between native and generic XDP. > > Fixes: e624d4ed4aa8 ("xdp: Extend xdp_redirect_map with broadcast support= ") > Cc: stable@kernel.org > Reported-by: Yuan Tan > Reported-by: Zhengchuan Liang > Reported-by: Xin Liu > Assisted-by: Codex:GPT-5.4 > Signed-off-by: Zhao Zhang > Signed-off-by: Ren Wei Reviewed-by: Toke H=C3=B8iland-J=C3=B8rgensen