From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 0F4AC3B2D00; Tue, 21 Jul 2026 20:34:16 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784666057; cv=none; b=CvlA20UPB1BZGV7bRi/P7WYT8yhsLpcBxoF6cZdDQNPY8rr7TYqp0aUosIL3C/jzFMepKj/TUjyVFUv/1WbTogT/363ExejwnEn/TeI4bmZwhUu/uVMwQ3LzKECyiDAKfpCZNXPdrdeTVhbOgVvyTFvu5uK5a/HQZigX+lmGR28= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784666057; c=relaxed/simple; bh=oqBVir21SmiOFwRjacar7vs7C13lP3s8/ShYr37sG4s=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=Wq0KyShzWBNropo+LYg52ydien+YGl4slFHx91oLAuXv9vhk1J0+P5hCPNzGqUruJIv4e3D77FK5OqTAT1OsLNDbYjytdoZ1olvwvsuOldcLA3kMcUmUBxz04pky9bVsezjThWA0QjFAQzH+iA4vVaSjXg4YSLE/MUW4MqpXY74= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=Bio0h6+d; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="Bio0h6+d" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 74AF31F000E9; Tue, 21 Jul 2026 20:34:15 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1784666056; bh=GTfES20Kz/e9nKE2OjOupNo0C/WiWre6Y1+UOrRFtiA=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=Bio0h6+dMsiy4ogaEg/5vMsgp3qLW0YQJ4gpN+lNGt1qQ3AVqvUXR7/05cTDbxRos ZNqOPgs594T0kbwATBDw+g5hnjB2y212QMHkyL6YhWCI2cgQGI1CVT/a3h11gxyJOu gKHcbwtqhvnzRF8Sn3CA48Yd7Vzr66d4Tc1GDbSs= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Qing Ming , "Michael S. Tsirkin" , Sasha Levin Subject: [PATCH 6.6 0537/1266] vhost/net: complete zerocopy ubufs only once Date: Tue, 21 Jul 2026 17:16:14 +0200 Message-ID: <20260721152453.881494187@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260721152441.786066624@linuxfoundation.org> References: <20260721152441.786066624@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.6-stable review patch. If anyone has any objections, please let me know. ------------------ From: Qing Ming [ Upstream commit 8f6898fe80794f2d7c3d38c1158c806e4074a1c4 ] vhost-net initializes one ubuf_info per outstanding zerocopy TX descriptor and hands it to the backend socket. The networking stack may then clone a zerocopy skb before all skb references are released. For example, batman-adv fragmentation reaches skb_split(), which calls skb_zerocopy_clone() and increments the same ubuf_info refcount. vhost_zerocopy_complete() currently treats every ubuf callback as a completed vhost descriptor. It dereferences ubuf->ctx, writes the descriptor completion state, and drops the vhost_net_ubuf_ref even when the callback only releases a cloned skb reference. A backend reset can therefore wait for and free the vhost_net_ubuf_ref while another cloned skb still carries the same ubuf_info. A later completion then dereferences the freed ubufs pointer. KASAN reports the stale completion as: BUG: KASAN: slab-use-after-free in vhost_zerocopy_complete+0x1d7/0x1f0 BUG: KASAN: slab-use-after-free in vhost_zerocopy_complete+0x101/0x1f0 vhost_zerocopy_complete skb_copy_ubufs __dev_forward_skb2 veth_xmit The freed object was allocated from vhost_net_ioctl() while setting the backend and freed through kfree_rcu()/kvfree_rcu_bulk after backend removal, while delayed skb completion still reached vhost_zerocopy_complete(). Honor the generic ubuf_info refcount before touching vhost state, and run the vhost descriptor completion only for the final ubuf reference. This matches the msg_zerocopy_complete() ownership rule for cloned zerocopy skbs. Fixes: bab632d69ee4 ("vhost: vhost TX zero-copy support") Signed-off-by: Qing Ming Signed-off-by: Michael S. Tsirkin Message-ID: <20260601104300.197210-1-a0yami@mailbox.org> Signed-off-by: Sasha Levin --- drivers/vhost/net.c | 15 +++++++++++---- 1 file changed, 11 insertions(+), 4 deletions(-) diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c index b26d9a8e4e0558..2953ab6e0c1d1c 100644 --- a/drivers/vhost/net.c +++ b/drivers/vhost/net.c @@ -390,13 +390,20 @@ static void vhost_zerocopy_signal_used(struct vhost_net *net, static void vhost_zerocopy_callback(struct sk_buff *skb, struct ubuf_info *ubuf_base, bool success) { - struct ubuf_info_msgzc *ubuf = uarg_to_msgzc(ubuf_base); - struct vhost_net_ubuf_ref *ubufs = ubuf->ctx; - struct vhost_virtqueue *vq = ubufs->vq; + struct ubuf_info_msgzc *ubuf; + struct vhost_net_ubuf_ref *ubufs; + struct vhost_virtqueue *vq; int cnt; - rcu_read_lock_bh(); + /* Only the final cloned skb reference completes the vhost descriptor. */ + if (!refcount_dec_and_test(&ubuf_base->refcnt)) + return; + + ubuf = uarg_to_msgzc(ubuf_base); + ubufs = ubuf->ctx; + vq = ubufs->vq; + rcu_read_lock_bh(); /* set len to mark this desc buffers done DMA */ vq->heads[ubuf->desc].len = success ? VHOST_DMA_DONE_LEN : VHOST_DMA_FAILED_LEN; -- 2.53.0