From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-wm1-f52.google.com (mail-wm1-f52.google.com [209.85.128.52]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id A2633343D80 for ; Thu, 16 Jul 2026 10:06:12 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.128.52 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784196374; cv=none; b=TOUTc5l2wKGc/PlwTS/3YILwdb5FVLpzWHCrGD6RyujUQFwcP7NrGNAXg/GCbACt8r/KQPLFz7Pa53f0g1tR7YUdoz1pjWfsDzSHdVT/L+T5JLC6zdEdKDYa9YG9gZ1ArHrXcYg8IrZejSXSiy9n5+nAXMgmJ6IFt23AAvaYHo8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784196374; c=relaxed/simple; bh=+ammkv9WmlsXieg1M/BdCjHugEumXiLSHhThR842jLU=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=FTq6otQXFd/Sb0D5Wrtu7GCQei+cx90XNxIqI+h6NYV2//ypDEQMvPnIErAfhowVyEQ+RDrm0i4Y+SFdrPfVZXyn9B4aSkjrhCkLjSvBzzj7BjTaXW+LF0O8wJ9aSoDkE0aoe1zHWw9WRS3DcI+sCEEzMUF0nuPzVQEbJ8hPyWs= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=readmodwrite.com; spf=none smtp.mailfrom=readmodwrite.com; dkim=pass (2048-bit key) header.d=readmodwrite-com.20251104.gappssmtp.com header.i=@readmodwrite-com.20251104.gappssmtp.com header.b=xVvLpbvZ; arc=none smtp.client-ip=209.85.128.52 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=readmodwrite.com Authentication-Results: smtp.subspace.kernel.org; spf=none smtp.mailfrom=readmodwrite.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=readmodwrite-com.20251104.gappssmtp.com header.i=@readmodwrite-com.20251104.gappssmtp.com header.b="xVvLpbvZ" Received: by mail-wm1-f52.google.com with SMTP id 5b1f17b1804b1-493b966dd74so26057865e9.3 for ; Thu, 16 Jul 2026 03:06:12 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=readmodwrite-com.20251104.gappssmtp.com; s=20251104; t=1784196371; x=1784801171; darn=vger.kernel.org; h=content-transfer-encoding:mime-version:message-id:date:subject:cc :to:from:from:to:cc:subject:date:message-id:reply-to:content-type; bh=4zobRwr1il7Vi209UdGxxH04APhzDHoeOJcQfGK80zc=; b=xVvLpbvZjS0j2PNK/QyhcNZgHnw4TrJzIDpIDChWZMxYmj5VHp0eN3L7mNrdmTEBho Gg9P+v92+pBSZtWGnPANDjWx5BInUa8EpexLHDtjueN1pxo1aqh95uzCQ0azuOiE9mJ5 QJlu4KqY55RO5/Hw4NONkBphcR+2/fWaqqWJkRD1b6dWGyuHI8Hm0eOKLCYbA6MIu2AW 7KT0Ddovk4UWzkFqeQp8xo3x9KCKAGg+ZW9B6GHFNZ7AmFZjMfLVJy/6NkyAhj02WCGG gyQeck8wzfLnY3Dk99IDq2r5dhBIYdL5k4qvZ0L8Yr8Jerd//umwLQLPAQmgNUJxT0vo 4Tbg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1784196371; x=1784801171; h=content-transfer-encoding:mime-version:message-id:date:subject:cc :to:from:x-gm-gg:x-gm-message-state:from:to:cc:subject:date :message-id:reply-to:content-type; bh=4zobRwr1il7Vi209UdGxxH04APhzDHoeOJcQfGK80zc=; b=jOOITt+pFAFZc9ABHR24NI+RftDp5YqeABVSVNrH2oLWyT036tpKan2Df6AmKpoSe6 v23ubTcR5e3qNMfgWXrkiQTz787QcqikWxW9KqDtXfdnnuSdP2SnkUEDOLBBd96nnvyj l+8cIfXM8IhUNYCzrRTiR9g7Hmc9Qt7MssyuRzg/6FxQFbogzZOs3zNkvGIiHrp0F3UB OtJ+Kqpy3beLHdlc4pL6i/PUneEDhrsFKQncbk1zCXRDPqAJEQ/PiNdcbTyARbxpjgrr Ec4g0cnw3gwcFPKziftfbBANKccelNnIg6LkjYQgyy6X9EurbMbP7el43iTxzLo+r/Uh nT3w== X-Forwarded-Encrypted: i=1; AHgh+RoOHjKe+cNhyxJ1nRwVuw69a/yFfjX9Y43aiVt8HniJU2bVXx1ebCCPkH4/LZx4ETeDPrs=@vger.kernel.org X-Gm-Message-State: AOJu0Yywc7tz2fk9FoH6HRCHYIT2g+JNLSUt8EhGsxi3BOPFrEvY1aGJ kUaIr4kEbcFrbUZUumXmbkuYOvHqpOeEn0a65FqvxLg1U2fqL5XbF1PHFEaEywgiXjZ9z438PsG LpDTBet8= X-Gm-Gg: AfdE7cmpoWoA5YreX4Urni57UwHm4TRnnXhDLuuGohIkBCZTDy8NJx5xtDAkhb4z4Ey M8ILqVvrkbDY0pPvk8iFOV3yy56bLcJUSdSjbgopcuo/lOXCO9r77Zc1HZbuKoTjOsXvnccc3pi 4CawbrQvXwut1Xv0GKzzEZLN6QNLjKKM0Wtc87mVmmIjGxexWMF9e4ekBWSfMTKRJ9kmfYxnAoM 0Nq93lSCOIPox12cI4ByrjareGZJ7zS4NHGfRAG0Ejh82Go6jNJXy6bIupwgQS08ZV2TJD530B5 H9CA/lnjReg3u+cjBRtERtws4DfQArLy7aDStScLUN959jdsQ/7zQEydcGVo4kK7FJD1aCTNPT0 IVlhxNwyrI0x1MXweSF8P5QNsokaOaVjpwLXINmqndmnXWtIOcy952o+RD7BIG58sNXjqjKvFsc o+1NJo X-Received: by 2002:a05:600c:c83:b0:493:c84c:2b57 with SMTP id 5b1f17b1804b1-4953c28b1a6mr63914085e9.29.1784196370491; Thu, 16 Jul 2026 03:06:10 -0700 (PDT) Received: from matt-Precision-5490.. ([2a09:bac6:37a8:2696::3d8:30]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-49541e9a7bbsm46976365e9.13.2026.07.16.03.06.08 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 16 Jul 2026 03:06:09 -0700 (PDT) From: Matt Fleming To: Alexei Starovoitov , Daniel Borkmann Cc: Andrew Lunn , "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Simon Horman , Jesper Dangaard Brouer , John Fastabend , Stanislav Fomichev , Lorenzo Bianconi , =?UTF-8?q?Toke=20H=C3=B8iland-J=C3=B8rgensen?= , bpf@vger.kernel.org, netdev@vger.kernel.org, stable@vger.kernel.org, kernel-team@cloudflare.com, Matt Fleming Subject: [PATCH bpf] veth: convert frag_list skbs before running XDP Date: Thu, 16 Jul 2026 11:06:05 +0100 Message-ID: <20260716100605.939654-1-matt@readmodwrite.com> X-Mailer: git-send-email 2.43.0 Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: Matt Fleming A frag_list skb can reach veth with data_len set but nr_frags zero. veth_convert_skb_to_xdp_buff() only converts skbs that are shared, locked, have frags[], or do not have enough headroom. It later uses skb_is_nonlinear() to decide whether to set XDP_FLAGS_HAS_FRAGS and xdp_frags_size. That exposes frag_list data to XDP as if it were stored in frags[], but frags[] is empty. AF_XDP copy mode can then trust the bogus XDP fragment metadata, walk an empty fragment entry, and crash in memcpy() from __xsk_rcv(). Route frag_list skbs through skb_pp_cow_data() before exposing them to XDP, and only advertise XDP frags when the resulting skb has frags[]. skb_copy_bits() already handles frag_list input, and skb_pp_cow_data() builds frags[] output with skb_add_rx_frag(), which is the representation XDP multi-buffer expects. Fixes: 718a18a0c8a6 ("veth: Rework veth_xdp_rcv_skb in order to accept non-linear skb") Cc: stable@vger.kernel.org Signed-off-by: Matt Fleming --- drivers/net/veth.c | 4 ++-- net/core/skbuff.c | 9 ++++----- 2 files changed, 6 insertions(+), 7 deletions(-) diff --git a/drivers/net/veth.c b/drivers/net/veth.c index 1c5142149175..efb24aae1f26 100644 --- a/drivers/net/veth.c +++ b/drivers/net/veth.c @@ -756,7 +756,7 @@ static int veth_convert_skb_to_xdp_buff(struct veth_rq *rq, u32 frame_sz; if (skb_shared(skb) || skb_head_is_locked(skb) || - skb_shinfo(skb)->nr_frags || + skb_shinfo(skb)->nr_frags || skb_has_frag_list(skb) || skb_headroom(skb) < XDP_PACKET_HEADROOM) { if (skb_pp_cow_data(rq->page_pool, pskb, XDP_PACKET_HEADROOM)) goto drop; @@ -771,7 +771,7 @@ static int veth_convert_skb_to_xdp_buff(struct veth_rq *rq, xdp_prepare_buff(xdp, skb->head, skb_headroom(skb), skb_headlen(skb), true); - if (skb_is_nonlinear(skb)) { + if (skb_shinfo(skb)->nr_frags) { skb_shinfo(skb)->xdp_frags_size = skb->data_len; xdp_buff_set_frags_flag(xdp); } else { diff --git a/net/core/skbuff.c b/net/core/skbuff.c index 18dabb4e9cfa..1e837d01a908 100644 --- a/net/core/skbuff.c +++ b/net/core/skbuff.c @@ -936,12 +936,11 @@ int skb_pp_cow_data(struct page_pool *pool, struct sk_buff **pskb, int err, i, head_off; void *data; - /* XDP does not support fraglist so we need to linearize - * the skb. + /* + * skb_copy_bits() handles both frags[] and frag_list input. If the + * copied skb remains non-linear, it uses frags[], which is the + * representation used by XDP multi-buffer. */ - if (skb_has_frag_list(skb)) - return -EOPNOTSUPP; - max_head_size = SKB_WITH_OVERHEAD(PAGE_SIZE - headroom); if (skb->len > max_head_size + MAX_SKB_FRAGS * PAGE_SIZE) return -ENOMEM; -- 2.43.0