From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=100.103.45.18 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1794590277; b=J79w+eNnnC0ZhsPNDHBOcJm+SJwvOgCb1j14V4UwwVQIQFrCV2hw4Jdns5RUhaFiRS9b /mnC9YhAyoWKlCwA2MuJsdAOXxNF4b3nN0LsXrUkWWNed2tSmtRanbAK/yMf9jzknvJn6 Eer/eil2/xRX92TZsQiYHmOjBiQ+xS20MIN4vxSvTtNJB1/OwmZFAuAhrYzIBb5kjfIX0 S6CJ6RxtPx+4VVSeZ6ARRBf768AQLNHDwg9ovmhc0qG70jZG12ljE8XZKybuM/MhNoMXS LWUko1Na6L2z6R05xhHj7SGG8fE362nC8EBpfDq4WczjuEr7j6pDPvtOUeAhiamP5hA== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1794590277; h=Received:DKIM-Signature:From:To:Cc:Subject:Date:Message-ID:X-Mailer: In-Reply-To:References:User-Agent:X-stable:X-Patchwork-Hint: MIME-Version:Content-Transfer-Encoding; bh=vzx3Ge9EkzZ84eDW4xagOA2b9ivTyi+wIB0Etqk3gcg=; b=WbiSoF9Dvwny5I3Nbz3CZHqqnynmrQ/xdGP5w7Ng4JaVijNwYEJ9h0VtyOtsEhjAmDzy l/HVlamhnYP0Oic9elh5ugQgj/wb9UOdkNDuA08spqWKq8Z8m935EgL4jygqrfezjE4CP IWPtPOWtWvhE3GzTMR+Ba7lYcNMH8Y9BkCw5LF6wWqECSw68BDVG0gtVgv8T5JuUKjROw obRqhbt6fYhN8W4jloi2ZkWVF6HqWwJ9s0oQZT2yLjDU3rjEJMhJi0JW8zMd5ypYbLOpd aPvZzyTZElMSMryN/UYEEYLXXuCsK6WHweFECNHnBly8NFcLP74Gq1eNup5Ix1Ut1Tg== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass header.d=linuxfoundation.org header.i=@linuxfoundation.org header.a=rsa-sha256 header.s=korg header.b="Ywqg/ydm"; arc=none smtp.remote-ip=100.103.45.18 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id AB02E60776DD; Fri, 13 Nov 2026 17:17:57 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.a=rsa-sha256 header.s=korg header.b=Ywqg/ydm Received: by smtp.kernel.org (Postfix) with ESMTPSA id 57AE71F000C4; Fri, 13 Nov 2026 17:17:57 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1794590277; bh=vzx3Ge9EkzZ84eDW4xagOA2b9ivTyi+wIB0Etqk3gcg=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=Ywqg/ydmkkIuPqVWP2DdhGs5kzHURdJXKnWfBb1wS61HZc6maKSAjRzoEQ47ukfYb 4Je5Fxb8jeFRhAh954b53FTkzUYoac7vdb3Kka5J3XO5Q4qLY7KCu/2MADaSRyGO3N 4ZHa4jae1NKiuZ+P/RnEryaJr2K3RTB9LYI5GULo= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Xie Yongji , Fang Xieyan , "Michael S. Tsirkin" , Sasha Levin Subject: [PATCH 6.18 267/686] vringh: bound top-level re-entry into indirect tables Date: Fri, 13 Nov 2026 10:46:40 -0500 Message-ID: <20261113153830.066789942@linuxfoundation.org> X-Mailer: git-send-email 2.56.0 In-Reply-To: <20261113153820.902362109@linuxfoundation.org> References: <20261113153820.902362109@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore X-Mailing-List: patches@lists.linux.dev List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.18-stable review patch. If anyone has any objections, please let me know. ------------------ From: Fang Xieyan [ Upstream commit f898439ace7f89922e853b43bcbfcd26ea2e0a98 ] In __vringh_iov(), the F_INDIRECT branch descends into the indirect table and continues before the descriptor accounting runs. A top-level indirect descriptor is therefore never charged to count. If such a descriptor sets NEXT to point back at itself, returning from the indirect table resumes at the same top-level descriptor, which is again not counted, so the walk never makes forward progress. Because count stays flat and indirect_count is reset to 0 on every return to the top-level table, neither bound in the loop check trips. A guest can spin the vringh worker at 100% CPU inside __vringh_iov(), an uninterruptible host DoS. Move the descriptor accounting above the indirect switch so that a top-level indirect descriptor is charged one top-level traversal step before the walk descends into its table, bringing this re-entry under the existing vrh->vring.num bound. Each top-level descriptor is still charged at most one step and indirect_count still bounds a single table, so legitimate chains (including the multiple-indirect case in tools/virtio/vringh_test.c) stay within vring.num, while a cyclic indirect descriptor is now rejected with -ELOOP. Fixes: dbd29e075228 ("vringh: Fix loop descriptors check in the indirect cases") Cc: Xie Yongji Cc: stable@vger.kernel.org Assisted-by: Hawkeye:GLM-5.3-flash Assisted-by: Qoder:Qwen3.8-Max Signed-off-by: Fang Xieyan Signed-off-by: Michael S. Tsirkin Message-ID: <20260922122955.69433-2-fangxy@xiaopeng.com> Signed-off-by: Sasha Levin --- drivers/vhost/vringh.c | 22 +++++++++++----------- 1 file changed, 11 insertions(+), 11 deletions(-) diff --git a/drivers/vhost/vringh.c b/drivers/vhost/vringh.c index 925858cc60964..c753a0cee240d 100644 --- a/drivers/vhost/vringh.c +++ b/drivers/vhost/vringh.c @@ -333,6 +333,17 @@ __vringh_iov(struct vringh *vrh, u16 i, if (unlikely(err)) goto fail; + if (up_next == -1) + count++; + else + indirect_count++; + + if (count > vrh->vring.num || indirect_count > desc_max) { + vringh_bad("Descriptor loop in %p", descs); + err = -ELOOP; + goto fail; + } + if (unlikely(desc.flags & cpu_to_vringh16(vrh, VRING_DESC_F_INDIRECT))) { u64 a = vringh64_to_cpu(vrh, desc.addr); @@ -358,17 +369,6 @@ __vringh_iov(struct vringh *vrh, u16 i, continue; } - if (up_next == -1) - count++; - else - indirect_count++; - - if (count > vrh->vring.num || indirect_count > desc_max) { - vringh_bad("Descriptor loop in %p", descs); - err = -ELOOP; - goto fail; - } - if (desc.flags & cpu_to_vringh16(vrh, VRING_DESC_F_WRITE)) iov = wiov; else { -- 2.53.0