From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-pl1-f181.google.com (mail-pl1-f181.google.com [209.85.214.181]) (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 5A1A140802B for ; Sun, 4 Oct 2026 07:34:35 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.214.181 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1791099281; cv=none; b=l9OxTbJB1VDHSMihPGb/PkxzCPePJUguuj1izck8laYGRezZLSg1Wyo+iRpgdX1NIrrr0ontxWbLALfNQiGWUpG20EFOjlhb2EUFc4hLTV7Li5l4lP6EsPu6+t6F/uGK6HiGnfKi4BPWyIXDjenIEDpqXO40tF/jorx6EuxTudg= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1791099281; c=relaxed/simple; bh=oV8I52EnEn4Do2vf3jRoStkeuMXWZFI+JGNnneSg3Ug=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=u8wz6zbJmz4F22wpHMIGOKaBNGrTM36FnapI/LRMebR0qTZux8comaNZJuAFvX4mX/Nqrlc+teQ6scB/0DxLkVzA1++xasE/1xWYUXwKbM/6OdlUKb9CFJGRSfzYv3yTlVuKh3RGxitp+agG8kGAHpJ56wDkZg6BaQkdpan8Jlw= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com; spf=pass smtp.mailfrom=gmail.com; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b=TlC846XP; arc=none smtp.client-ip=209.85.214.181 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=gmail.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="TlC846XP" Received: by mail-pl1-f181.google.com with SMTP id d9443c01a7336-2e30b9f1441so9238855ad.3 for ; Sun, 04 Oct 2026 00:34:33 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20251104; t=1791099271; x=1791704071; 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=3TSxZwHRoZMu3vBmEpKbk/Zl8R7mBDI5Id5VQd4Apzw=; b=TlC846XPO2Gv+JsPUu5xUx66cWpftMkB/Z2wAhQWBpx/7mXVNPBCIUSnLiLVna7gCO t99eU3AcaHJRvCi4mkwrsuIhRMrH9FbdI3ylKBv91MO0v/fK9Q37EG4LwYPPn+AiZF1j BpP0PXJL9CbKTjPVT0e0fXuhWA1ch8wOgTy1nGv3fBszLn2hrPqIiH5/E0ZUdjJ6nDXC 6MqyWJZWHRYgE+1cqtAuA+pahi/ADtvexVJYyZ3iamzNJjRBYFWjwXEI1+/5Q6bnPGNQ 72qRT4b5mVb4TW75tQkwMce3T2PayOTyQI2o/RgDRoazTIdXxpDGEOlPSZ2KEhukV5NM mjQw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20260707; t=1791099271; x=1791704071; 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=3TSxZwHRoZMu3vBmEpKbk/Zl8R7mBDI5Id5VQd4Apzw=; b=PKHIFijlzVEl76zqVFTWoYP8ZjvhuYciv0WetoW+lfYPJDLgMYZQg46jddh/YIYkjv b0uLm3hvmP7puo4GlgKFpmlqSOsqfNRrcf4gHiLDiMV66edFLUrtAc9b2PxcnGJ5AT+l OonnisUMndHNPhrSF0YVbOwly1cOZoswGzgFw9TU7j74hqb01SmBtDbjW0aGHdL4xh35 Yeh6qemm29Irlf39p1eij6kHTJaNtQcc8+aCZTGk155KAjY6GUso2RE8Ushg2DKbaMxV zAwohFWfm7JmkQ673SCWxVtIjSZtAb9pRINTva8pMiWbgcv4XftZMcimaf43F7sB7MkK vvIQ== X-Forwarded-Encrypted: i=1; AKwUvBznD7Ejd4OJkRlUAZTC70Uhaiuv7xRWXGg1zxn1smqGmKhC2eOYTUaSa8XGAb2/K1hoVu49dqI=@vger.kernel.org X-Gm-Message-State: AFq9FYLTNt1i7XW2MVP9Xtr5rs9ad7teUq6pJcPk8FBtS2ybJUkdxRyr iOBdLf+j8C3Jkfka26ZPQMDVlsgM9mpylLGwsp1JGRmVqMXH5OSp2X6d X-Gm-Gg: AYBFou2cge23iutsdKh5idznm/IuBhWxKV1dRVlGRsQwpe7Ioi9cVf2UirqWEHGmPg+ ilyNbssxa975V98R3Lkoo20QbzkO8gBwagKmi+BH648L68u/07mC7FJPysRhcktzvQ0/uvLXKBo VEo9mZIgUUYw0J7xf9wmGumcsfKhKEaPv01z4BNJX5oQt9EsSMH9kTUoYff8QFOIYJD5gRLeami x3fP3RAH7mjsKG8+alzOe/rkwiPcsmwabj918oNc0UHBm5s3dJq17bnfO0NTmQfW4hqTdVTATDp 8HR2Ypeylhnp/818i/ll1J0CUbuSVOO5M3sL9jIXLTUXKOGUTopKIAxsVTkpyeuB8Up0/6HKTP9 9qlhhxTzI1rWIvIgHAtbGvEEoZUfiGDu6IpTAb7SMPVNgzRO7Rg7pQ6DtCStTR+RdPUG9nQJLCR vXxX2EB+ciJqW0a9HoKKxW9cWRP9b1wP6t2Jc27YUbWNg+2eTuLmgXxbQl7RdYjG9sU6kqQtqtX /0CVgqhYb0= X-Received: by 2002:a17:902:f686:b0:2e2:dc50:16a8 with SMTP id d9443c01a7336-2e510573f7cmr31772435ad.27.1791099271346; Sun, 04 Oct 2026 00:34:31 -0700 (PDT) Received: from ancienth-X870E-Nova-WiFi ([125.186.72.2]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-2e49f7312aasm21800865ad.79.2026.10.04.00.34.27 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 04 Oct 2026 00:34:29 -0700 (PDT) From: Daehyeon Ko <4ncienth@gmail.com> To: Stefan Hajnoczi , Stefano Garzarella Cc: Daehyeon Ko <4ncienth@gmail.com>, "Michael S . Tsirkin" , Jason Wang , =?UTF-8?q?Eugenio=20P=C3=A9rez?= , Xuan Zhuo , Will Deacon , kvm@vger.kernel.org, virtualization@lists.linux.dev, netdev@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH net v2] vhost/vsock: size receive SKBs from declared payload Date: Sun, 4 Oct 2026 16:34:19 +0900 Message-ID: <20261004073419.4039011-1-4ncienth@gmail.com> X-Mailer: git-send-email 2.55.0 Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit vhost_vsock_alloc_skb() allocates an skb from the total guest descriptor length before reading hdr->len. Descriptor capacity and declared payload length are independent, so a guest can supply a large descriptor with a zero or short payload. On Linux v7.2, 455 zero-payload packets with 64 KiB descriptors retained 30,255,680 bytes on a 256 KiB receive buffer while rx_bytes and buf_used stayed zero. A full-payload control retained 265,984 bytes. The existing SKB_TRUESIZE(0) budget caps skb count but does not account for the descriptor-sized allocation. Repeating this across connections can exhaust host kernel memory. Trimming after allocation is insufficient. Linear skbs retain their full head, while a nonlinear payload exceeding head tailroom can retain its first page fragment. Copy the header into a stack object, validate hdr->len before allocating, and size the skb from the declared payload plus the header. This keeps the allocation proportional to receive accounting for both linear and nonlinear skbs. Use payload_len > len - sizeof(hdr) for validation. This avoids addition overflow on 32-bit hosts and ensures payload_len fits the subsequent int-length copy path. Fixes: ab9aa2f3afc2 ("vhost/vsock: Allocate nonlinear SKBs for handling large receive buffers") Cc: stable@vger.kernel.org Assisted-by: LLM Signed-off-by: Daehyeon Ko <4ncienth@gmail.com> --- Changes in v2: - validate the header before allocation with an overflow-safe bounds check; - size the skb from declared payload and remove the global trim-helper change; - remove the generic clean-validation statement from the changelog; and - add Will Deacon to Cc. v1: https://lore.kernel.org/netdev/20260930044147.3818241-1-4ncienth@gmail.com/ Built and booted on v7.2 with KASAN, UBSAN and LOCKDEP. A focused allocation/queue probe retained 436,800 and 582,400 bytes for 455 zero and 341-byte packets, versus 30,255,680 bytes for the vulnerable zero case. No KASAN report, WARN, oops or panic occurred. The probe injects skbs in-kernel rather than through a live guest virtqueue. drivers/vhost/vsock.c | 34 ++++++++++++++++------------------ 1 file changed, 16 insertions(+), 18 deletions(-) diff --git a/drivers/vhost/vsock.c b/drivers/vhost/vsock.c index abed1fbcf66cc5..35f75e23c7497e 100644 --- a/drivers/vhost/vsock.c +++ b/drivers/vhost/vsock.c @@ -364,7 +364,7 @@ static struct sk_buff * vhost_vsock_alloc_skb(struct vhost_virtqueue *vq, unsigned int out, unsigned int in) { - struct virtio_vsock_hdr *hdr; + struct virtio_vsock_hdr hdr; struct iov_iter iov_iter; struct sk_buff *skb; size_t payload_len; @@ -382,34 +382,32 @@ vhost_vsock_alloc_skb(struct vhost_virtqueue *vq, len > VIRTIO_VSOCK_MAX_PKT_BUF_SIZE + VIRTIO_VSOCK_SKB_HEADROOM) return NULL; - /* len contains both payload and hdr */ - skb = virtio_vsock_alloc_skb(len, GFP_KERNEL); - if (!skb) - return NULL; - iov_iter_init(&iov_iter, ITER_SOURCE, vq->iov, out, len); - hdr = virtio_vsock_hdr(skb); - nbytes = copy_from_iter(hdr, sizeof(*hdr), &iov_iter); - if (nbytes != sizeof(*hdr)) { + nbytes = copy_from_iter(&hdr, sizeof(hdr), &iov_iter); + if (nbytes != sizeof(hdr)) { vq_err(vq, "Expected %zu bytes for pkt->hdr, got %zu bytes\n", - sizeof(*hdr), nbytes); - kfree_skb(skb); + sizeof(hdr), nbytes); return NULL; } - payload_len = le32_to_cpu(hdr->len); + payload_len = le32_to_cpu(hdr.len); + + /* The pkt is too big or the length in the header is invalid */ + if (payload_len > len - sizeof(hdr)) + return NULL; + + /* Allocate only for the payload declared in the header. */ + skb = virtio_vsock_alloc_skb(payload_len + sizeof(hdr), GFP_KERNEL); + if (!skb) + return NULL; + + memcpy(virtio_vsock_hdr(skb), &hdr, sizeof(hdr)); /* No payload */ if (!payload_len) return skb; - /* The pkt is too big or the length in the header is invalid */ - if (payload_len + sizeof(*hdr) > len) { - kfree_skb(skb); - return NULL; - } - virtio_vsock_skb_put(skb, payload_len); if (skb_copy_datagram_from_iter(skb, 0, &iov_iter, payload_len)) { base-commit: 6dc989ea46b96ce170840174b4a38c4a387fb005 -- 2.55.0