From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-qk1-f179.google.com (mail-qk1-f179.google.com [209.85.222.179]) (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 CBCA712B94 for ; Mon, 22 Jun 2026 12:47:55 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.222.179 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1782132477; cv=none; b=cjH/ubmgvOrmpI0Uohsk3Kn+WpocDcF+A4SxZl98Mwju1x51a8lq5yvazmROk/V0sqz5TNzrOZ0C7kO/W6u7QUQIf171yjLHWOSkUCtfL0A3eQCLwitTToO3vlmtNOAayvmBrlCprFMonhtzr+DtBMDTW+2cdlRUxzFwBHk1fnE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1782132477; c=relaxed/simple; bh=BMt9S2GVKFeVNhMZL7H6LKXCnpEdYdYF+DJNnRuXXcI=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=UpJwtaPUDUu4mXCGimvpunPUjDeeiN5am6XdX1vjkDgrfNd1ca+A38nQGsErq0xCvM89ZG5XDQdE8oev2pilWjeojIObG2FY3EnpbmZtkmLlSX20Yt7iLQ3KQGHs8Epn50GXVrRMiPSUm9BfJ0Fi6+yn9xkopA6F/yaCq6Jsy7w= 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=YUq8KEsw; arc=none smtp.client-ip=209.85.222.179 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="YUq8KEsw" Received: by mail-qk1-f179.google.com with SMTP id af79cd13be357-915c48e6ae2so342338785a.2 for ; Mon, 22 Jun 2026 05:47:55 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20251104; t=1782132475; x=1782737275; 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; bh=EZ7pZRYHyAL9Y6GeFGdymSQ0UmhOlD3YoloBKxZNcFU=; b=YUq8KEswbDL55ZNQ1L8Rov7jqX+sW1p8/hni+eJlJDqTiw7uUcEXPxhmvbwGeSHDA1 36kUVXsyOCIgYBUK3W2JX7E0wjZ+byZ/GOIC5oK8AeNnUGZLILeGtCdhTCZDSwC6a2dV cBHsKC4NyqKhfX5wxopJhI1kXCxvxJwYOE2C7lxgFGst4/nHKMg5XeGWVsSB2HW//Tj1 xxF4LpkxYpfY2sr62wHb3UcU1B+eokHBuKGzcs/0FIiNDYpFmfHr4NnNxT9V3e1BVZTH WCcQUf/5GbR9Pqc8tTOf3YUNvH8+ewM/reVnl3rJnqyqvkUaaKUYQNPjvNJDKTHEzX6u UD4g== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1782132475; x=1782737275; 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; bh=EZ7pZRYHyAL9Y6GeFGdymSQ0UmhOlD3YoloBKxZNcFU=; b=MBIp+0k0s5vef87uf4mLj+Fm3ibGX5xr1chd065W3hrVOnMi7v2ZC8QhfZ3wlGv3mD QCvtTSM3Gf9ujsSi9DzqXHs5f02MzNm15Dr0RRmx7i7QypvLcTdjfLO6BodFL+2MGNdO VrogrWxYipQx2XZDzp5onRheCzdM9AnsILGCnaGQOUqIgqZLn9QQ2ma7D6WPJH1vq7Ig DI9XnUP4JxfbYuts12IKC7J+b1TznYgEtV98by0NQTY2n5J+zw5m6uSOASc8WOive0u5 XBpKww+oFDOx0+e4i3m2diKWnEiZkw4L4r6zDAB59/0TILATJTT8TSARgsVqNjq/7V43 cVSw== X-Forwarded-Encrypted: i=1; AFNElJ/kOtTvgGwaUACGRAKj9LnfwCnoDpzcol1qEXKKI8Y0rq09HQvDUKrJa+ubTgHgDrYBrqjc4hMNjhBStQc=@vger.kernel.org X-Gm-Message-State: AOJu0YxE3PTUXzJXOr1Gbchemyk2okXe+R+24k+beEgbmIJ/tw/QczLh /QDdm2p7OP5mgJdpwCN+cfP4ELBByoBW685NpwxvEGLswXXcT1CcRzC3 X-Gm-Gg: AfdE7cn6iDmYTM4kiyT5uJuHgZ7LYwlVdN9/BXfRx4+ONLxw4sm/2/7vsXqO+cXsBS/ w/VHnZR6X3CrAbxZGnw9dk4yyJjZe203avA255GsULD19MsQ3yzJsTYJN3MLyL6bXyRKxi3gaeR 2oGOps0OFxrzr6tPotrx+C1q4kvIhxQs9QQPZg5ZDq2MZSmBJPCk+/RQ0wp8VVzEDyXcOwQkQEr 4XhFeS3+nbz+lQWUqHkj4/XxfP9WXY/FIp7EQATCSzp3TbR3Voml6NQt2eUJPntV3nk7Hd4HrBU bYOaQKjGUhRadoE4eo8TYTScwW9SkcRXDfcdrPQSW7e36NmQzl+OSz+mEPcOLogfi+HPkJymUKq /1iBupfzORNWWl6hSDhEkAZmV93/Kkbrl6IbBnomMaHaoW3feaS4yEJ1kqcpWskcw+XyBji6OiM up8p/LgPHXmaqXptEkPEPYnNV20q1nNl+G9Y6D3qqoE6KPJjMDCvLo6BW54RQiy1esN7Efii1iO Q2KcM7wPrzOqlzjOAEROkKgC36qkkjDFVGhxxusrOg= X-Received: by 2002:a05:620a:2945:b0:915:b852:4354 with SMTP id af79cd13be357-9208f15a21dmr2300093785a.9.1782132474635; Mon, 22 Jun 2026 05:47:54 -0700 (PDT) Received: from server0.tail6e7dd.ts.net (c-68-48-65-54.hsd1.mi.comcast.net. [68.48.65.54]) by smtp.gmail.com with ESMTPSA id af79cd13be357-921d7f5127fsm972531885a.17.2026.06.22.05.47.53 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 22 Jun 2026 05:47:54 -0700 (PDT) From: Michael Bommarito To: Richard Weinberger , Anton Ivanov , Johannes Berg Cc: Kees Cook , Tiwei Bie , linux-um@lists.infradead.org, linux-kernel@vger.kernel.org Subject: [PATCH] um: virtio_uml: fix heap overflow in vhost_user_get_config() Date: Mon, 22 Jun 2026 08:47:50 -0400 Message-ID: <20260622124750.1694957-1-michael.bommarito@gmail.com> X-Mailer: git-send-email 2.53.0 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 7bit vhost_user_get_config() sizes its reply buffer from header + payload: size_t payload_size = sizeof(msg->payload.config) + cfg_size; size_t msg_size = sizeof(msg->header) + payload_size; ... msg = kzalloc(msg_size, GFP_KERNEL); but then receives the response with msg_size as the payload cap: rc = vhost_user_recv_resp(vu_dev, msg, msg_size); vhost_user_recv() reads the header, then full_read()s header.size bytes into &msg->payload after checking only "size > max_payload_size". The payload area is msg_size - sizeof(msg->header) == payload_size bytes, so passing msg_size as the cap lets a peer set header.size up to msg_size and write sizeof(struct vhost_user_msg_header) (12) bytes past the end of the kzalloc(msg_size) buffer -- a slab out-of-bounds write of peer-controlled content. Pass payload_size, which is the size the payload area was allocated for. A malicious or compromised vhost-user backend triggers this during device probe (vu_get -> vhost_user_get_config) with no guest action, which matters in the confidential-computing model where the guest does not trust the device backend. Fixes: 5d38f324993f ("um: drivers: Add virtio vhost-user driver") Cc: stable@vger.kernel.org Assisted-by: Claude:claude-opus-4-8 Signed-off-by: Michael Bommarito --- Reproduced on a UML KASAN build (ARCH=um, CONFIG_KASAN=y) off this base. A stub vhost-user backend that answers GET_CONFIG with header.size set to the full msg_size makes vhost_user_recv() full_read() 12 bytes past the kzalloc'd reply buffer; KASAN reports a slab-out-of-bounds write in vhost_user_get_config(). With this patch the oversized reply is rejected (-EPROTO) and KASAN is clean. Benign control: a correctly-sized GET_CONFIG reply succeeds on both stock and patched. Before/after logs available on request. arch/um/drivers/virtio_uml.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/arch/um/drivers/virtio_uml.c b/arch/um/drivers/virtio_uml.c index 7425a8548141a..38e960bec9e65 100644 --- a/arch/um/drivers/virtio_uml.c +++ b/arch/um/drivers/virtio_uml.c @@ -568,7 +568,7 @@ static void vhost_user_get_config(struct virtio_uml_device *vu_dev, goto free; } - rc = vhost_user_recv_resp(vu_dev, msg, msg_size); + rc = vhost_user_recv_resp(vu_dev, msg, payload_size); if (rc) { vu_err(vu_dev, "receiving VHOST_USER_GET_CONFIG response failed: %d\n", base-commit: ef0c9f75a19532d7675384708fc8621e10850104 -- 2.53.0