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Tue, 02 Jun 2026 10:11:12 -0700 (PDT) Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset=UTF-8 Date: Tue, 02 Jun 2026 13:11:08 -0400 Message-Id: To: "Ren Wei" , , Cc: , , , , , , , , , , , , , , , , , , , Subject: Re: [PATCH bpf v2] bpf: devmap: reject fragmented frames in clone-based broadcasts From: "Emil Tsalapatis" X-Mailer: aerc 0.21.0-0-g5549850facc2 References: <21c2d153dd25603d359069a02bf06779b51f6423.1780385378.git.zzhan461@ucr.edu> In-Reply-To: <21c2d153dd25603d359069a02bf06779b51f6423.1780385378.git.zzhan461@ucr.edu> On Tue Jun 2, 2026 at 4:43 AM EDT, Ren Wei wrote: > 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: Emil Tsalapatis > changes in v2: > - Add the same fragmented-packet restriction to generic XDP > dev_map_redirect_clone() so clone-based broadcast behavior stays > aligned with the native XDP path. > - v1 link: https://lore.kernel.org/all/4b596825bccc64d03e0c2e0db4dceb12c7= f5cf47.1780176829.git.zzhan461@ucr.edu/ > > kernel/bpf/devmap.c | 7 +++++++ > 1 file changed, 7 insertions(+) > > diff --git a/kernel/bpf/devmap.c b/kernel/bpf/devmap.c > index cc0a43ebab6b..5b9eac5342a9 100644 > --- a/kernel/bpf/devmap.c > +++ b/kernel/bpf/devmap.c > @@ -581,6 +581,10 @@ static int dev_map_enqueue_clone(struct bpf_dtab_net= dev *obj, > { > struct xdp_frame *nxdpf; > =20 > + /* Frags live outside the linear frame and cannot be cloned safely. */ > + if (unlikely(xdp_frame_has_frags(xdpf))) > + return -EOPNOTSUPP; > + > nxdpf =3D xdpf_clone(xdpf); > if (!nxdpf) > return -ENOMEM; > @@ -726,6 +730,9 @@ static int dev_map_redirect_clone(struct bpf_dtab_net= dev *dst, > struct sk_buff *nskb; > int err; > =20 > + if (unlikely(skb_is_nonlinear(skb))) > + return -EOPNOTSUPP; > + > nskb =3D skb_clone(skb, GFP_ATOMIC); > if (!nskb) > return -ENOMEM;