From: Zhao Zhang Date: Tue, 2 Jun 2026 08:43:33 +0000 (+0800) Subject: bpf: Reject fragmented frames in devmap X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=aa496720618f1a6054f1c870bf10b4f6c99bf656;p=thirdparty%2Flinux.git bpf: Reject fragmented frames in devmap 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 Reviewed-by: Toke Høiland-Jørgensen Link: https://lore.kernel.org/r/21c2d153dd25603d359069a02bf06779b51f6423.1780385378.git.zzhan461@ucr.edu Signed-off-by: Alexei Starovoitov --- 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_netdev *obj, { struct xdp_frame *nxdpf; + /* Frags live outside the linear frame and cannot be cloned safely. */ + if (unlikely(xdp_frame_has_frags(xdpf))) + return -EOPNOTSUPP; + nxdpf = xdpf_clone(xdpf); if (!nxdpf) return -ENOMEM; @@ -726,6 +730,9 @@ static int dev_map_redirect_clone(struct bpf_dtab_netdev *dst, struct sk_buff *nskb; int err; + if (unlikely(skb_is_nonlinear(skb))) + return -EOPNOTSUPP; + nskb = skb_clone(skb, GFP_ATOMIC); if (!nskb) return -ENOMEM;