From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-wr1-f54.google.com (mail-wr1-f54.google.com [209.85.221.54]) (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 4FFB6470E8A for ; Wed, 22 Jul 2026 19:19:31 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.221.54 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784747974; cv=none; b=FwJOunX1qtp6ueIDLvLWqZZnt9P4rPUb2A5xpzB9lPizqnxFr7yWPjBedcvmLgGy4CHSrWycNmBmF2wyT/RODccQk3O8qqTzB0mLi5q1C5jyYYgHeU/nBlNoctuiLpOtMsAQsuYg5oSSGX5QWsOHOcDhMuctMIvR7rYU1bNCgOs= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784747974; c=relaxed/simple; bh=Jb9J5bSOSje9FMdG7C+lQp/nEJBkbTNQ6Tu3vF6YLm4=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=ITSgrI1aSa7rvwlXpcmr7VbEkv4RdErm1n8WLtDSE2EvENVpyaNL/+GEFtlasPWD01JR30/Rk7V1uXSSqsMmFGkJBzbcl7XGI3GgY9hMWv2tQ+bkboePba8Nofc8PoNHWiF0TKlBiuVjwyKNOlQn7WJ9zziUjmleGpkp1RfWzK4= 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=KWnoGLja; arc=none smtp.client-ip=209.85.221.54 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="KWnoGLja" Received: by mail-wr1-f54.google.com with SMTP id ffacd0b85a97d-47db714766aso3884786f8f.0 for ; Wed, 22 Jul 2026 12:19:31 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=readmodwrite-com.20251104.gappssmtp.com; s=20251104; t=1784747969; x=1785352769; 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=pnInvCDAwEksrdCAmMtd6TY5IpoNHnNiOOgeViffG5c=; b=KWnoGLjaztBwfvaNzv3hM8DLIpDdS0MGN/bpFMCS1lIM0PYf7kzJqsX+d3kMWptqx5 hLRpjsTf0oAnwAdEBRiBpMMc1lbIYRv5diN4U4M/vhYcbiQxWwqajKEvzttN3xsP4hRe sRYh1ngrIyxB+MnZP9/yqnDzzqHs0XjYMlhAJ04MbHikJ6X/wGNmHmsmt3QuJ4wyUWAB phk0hH873T4tdw8Kr6aoFHL6us7YTvrlzIvYBLLWUg41ZYpqW1WkHuVDyjrrELXGfBEI 3kNWiRGjJMAtluPcKd/Aa+2pZhg6NUC0+u9IscRiRmRRReF1nuQ5bMtrqtGBbTQTSfD2 efBA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1784747969; x=1785352769; 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=pnInvCDAwEksrdCAmMtd6TY5IpoNHnNiOOgeViffG5c=; b=XkQ5Kj4Dkc+a/YCBl9UqQXqHGOfmuAL8PzW7dfGDPg5Xqr/L5nHlMRYYCEImyy4T2P XxcXLwIXH1r64B6LZQf1M5FcPhOK/e2uBrbzlwH/UPTWtVpeuSqAsJpO/g3SuV1xwZPI H0ogvaa109xA3P00ZVOdM7dDaVb1eHuWAO0wpCEXFnW6fFUqffvxfUAt4G1Q9KSNFhAg vfi+e+O0w6LBqubA9/12Uac3dzfGXto6psCoqoMPuaFV041+OCYIbJ3npcFl27CUihLF UsmLIUKOdNX45PlGZ4ZwQCgoAb0hRP9Ql8HDSWUwFnCp4a+8nkeAhvdhihv8X/4Xf1d9 3YTA== X-Forwarded-Encrypted: i=1; AHgh+RpTc84VxjYs0BRD4FsnvxHv6GnfoGq/wnDqMLPM1EA/hT0JcYrE9/lUN6sWQyP37hg20fc=@vger.kernel.org X-Gm-Message-State: AOJu0Yz+ggcaZT8OFz2epPmMWvW8uPK+psq9c8EyxSZ/9uIbcDZ06JR0 XLgagU3cGnWK7IzuAvQIpf8P6naImDq23VqJ8IkGT3VtiO9q71orRfT2urhbZtlJgn4= X-Gm-Gg: AR+sD10JMHCUM/iHEqqgOWDH6P5hD9kS9x4RTbGD4S8JcZsE6lnOINTiDJEfZJn0Td5 WseEAYFNCSodsEGRVoResTIqPpcgH2vnzS+Ztfvwgf8Ypm+FX1tyYhOZoXgqnKnDX+2Aj1yH7RS hdt5Zji+rKUFk5YKo2wJcHhuZ+xiPGBcXExSXrp57SsIrCRuIT4rZv5wBC6+weWGb/uP1xJwX3K QDeiYkoCw0FbsMPaQ5IdnNxk2OYlrK3WRh2F06fZjOaNM3lJisAd5/nuuwOWh5bwokRMbJwwfmm 3BAZWmVB0puJ+A3CeC2eU1f/U075hcRHij5JdrwMLMuGZEMdiiApHAG9caDKz+GimqTs7zwHN7i H9nQtHGrPgQbnVo84adjfFTT3ofkz80kpAszQsShgRkfhp4cQFzfdr8kAClDC/XGMTWV1ssU7Gp pT5JMN X-Received: by 2002:a05:6000:25e2:b0:47f:537b:d5d0 with SMTP id ffacd0b85a97d-47f840c95admr7850328f8f.28.1784747969382; Wed, 22 Jul 2026 12:19:29 -0700 (PDT) Received: from matt-Precision-5490.. ([2a09:bac6:37a8:26dc::3df:4d]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-47f85c67339sm8862982f8f.31.2026.07.22.12.19.27 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 22 Jul 2026 12:19:28 -0700 (PDT) From: Matt Fleming To: Andrew Lunn , "David S . Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Simon Horman Cc: Alexei Starovoitov , Daniel Borkmann , 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 net v3] veth: convert frag_list skbs before running XDP Date: Wed, 22 Jul 2026 20:19:25 +0100 Message-ID: <20260722191925.2192070-1-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 non-linear 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 --- Changes in v3: - Target net instead of bpf. - Add Return: to the skb_pp_cow_data() kerneldoc. Changes in v2: - Use skb_is_nonlinear() in veth_convert_skb_to_xdp_buff(). - Move the skb_pp_cow_data() comment into kerneldoc. drivers/net/veth.c | 4 ++-- net/core/skbuff.c | 18 ++++++++++++------ 2 files changed, 14 insertions(+), 8 deletions(-) diff --git a/drivers/net/veth.c b/drivers/net/veth.c index 1c5142149175..00e34afd858e 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_is_nonlinear(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..ba3dbac80fb4 100644 --- a/net/core/skbuff.c +++ b/net/core/skbuff.c @@ -927,6 +927,18 @@ static void skb_clone_fraglist(struct sk_buff *skb) skb_get(list); } +/** + * skb_pp_cow_data() - copy skb data into page-pool backed storage + * @pool: page pool to allocate from + * @pskb: pointer to skb pointer, replaced with the copied skb on success + * @headroom: headroom to reserve in the copied 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. + * + * Return: 0 on success or a negative errno on failure. + */ int skb_pp_cow_data(struct page_pool *pool, struct sk_buff **pskb, unsigned int headroom) { @@ -936,12 +948,6 @@ 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. - */ - 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