From nobody Thu Dec 18 13:01:50 2025 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id E5EB0C32774 for ; Tue, 23 Aug 2022 08:14:18 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S242347AbiHWIOP (ORCPT ); Tue, 23 Aug 2022 04:14:15 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:32924 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S242076AbiHWIKf (ORCPT ); Tue, 23 Aug 2022 04:10:35 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id C4DB3696F5; Tue, 23 Aug 2022 01:07:33 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 61742611A8; Tue, 23 Aug 2022 08:07:33 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 4EB65C433D6; Tue, 23 Aug 2022 08:07:32 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1661242052; bh=h3xjcasmKH79T4Xe1CGuqxknob4/8v+qLXk+cPNXymg=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=CYRNaDX8qjXiFoN5DsLPZJz8f4FizKWSokAzBXomYZ0sgdNd/8oi16wl483kqV9Pr nJuJfIvcibeBAkymKNaQELkZdBZ2FNyM+83CU0r4jLP44yjMc9ZdB7WEJCYVXEQVhK oF442carRbgFkkpdl5XvnJxwa0Yd4Sgb8shsBNfE= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Cezar Bulinaru , Willem de Bruijn , "David S. Miller" Subject: [PATCH 5.19 051/365] net: tap: NULL pointer derefence in dev_parse_header_protocol when skb->dev is null Date: Tue, 23 Aug 2022 09:59:12 +0200 Message-Id: <20220823080120.322529519@linuxfoundation.org> X-Mailer: git-send-email 2.37.2 In-Reply-To: <20220823080118.128342613@linuxfoundation.org> References: <20220823080118.128342613@linuxfoundation.org> User-Agent: quilt/0.67 MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" From: Cezar Bulinaru commit 4f61f133f354853bc394ec7d6028adb9b02dd701 upstream. Fixes a NULL pointer derefence bug triggered from tap driver. When tap_get_user calls virtio_net_hdr_to_skb the skb->dev is null (in tap.c skb->dev is set after the call to virtio_net_hdr_to_skb) virtio_net_hdr_to_skb calls dev_parse_header_protocol which needs skb->dev field to be valid. The line that trigers the bug is in dev_parse_header_protocol (dev is at offset 0x10 from skb and is stored in RAX register) if (!dev->header_ops || !dev->header_ops->parse_protocol) 22e1: mov 0x10(%rbx),%rax 22e5: mov 0x230(%rax),%rax Setting skb->dev before the call in tap.c fixes the issue. BUG: kernel NULL pointer dereference, address: 0000000000000230 RIP: 0010:virtio_net_hdr_to_skb.constprop.0+0x335/0x410 [tap] Code: c0 0f 85 b7 fd ff ff eb d4 41 39 c6 77 cf 29 c6 48 89 df 44 01 f6 e8 = 7a 79 83 c1 48 85 c0 0f 85 d9 fd ff ff eb b7 48 8b 43 10 <48> 8b 80 30 02 0= 0 00 48 85 c0 74 55 48 8b 40 28 48 85 c0 74 4c 48 RSP: 0018:ffffc90005c27c38 EFLAGS: 00010246 RAX: 0000000000000000 RBX: ffff888298f25300 RCX: 0000000000000010 RDX: 0000000000000005 RSI: ffffc90005c27cb6 RDI: ffff888298f25300 RBP: ffffc90005c27c80 R08: 00000000ffffffea R09: 00000000000007e8 R10: ffff88858ec77458 R11: 0000000000000000 R12: 0000000000000001 R13: 0000000000000014 R14: ffffc90005c27e08 R15: ffffc90005c27cb6 FS: 0000000000000000(0000) GS:ffff88858ec40000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000000000000230 CR3: 0000000281408006 CR4: 00000000003706e0 Call Trace: tap_get_user+0x3f1/0x540 [tap] tap_sendmsg+0x56/0x362 [tap] ? get_tx_bufs+0xc2/0x1e0 [vhost_net] handle_tx_copy+0x114/0x670 [vhost_net] handle_tx+0xb0/0xe0 [vhost_net] handle_tx_kick+0x15/0x20 [vhost_net] vhost_worker+0x7b/0xc0 [vhost] ? vhost_vring_call_reset+0x40/0x40 [vhost] kthread+0xfa/0x120 ? kthread_complete_and_exit+0x20/0x20 ret_from_fork+0x1f/0x30 Fixes: 924a9bc362a5 ("net: check if protocol extracted by virtio_net_hdr_se= t_proto is correct") Signed-off-by: Cezar Bulinaru Reviewed-by: Willem de Bruijn Signed-off-by: David S. Miller Signed-off-by: Greg Kroah-Hartman --- drivers/net/tap.c | 20 +++++++++++--------- 1 file changed, 11 insertions(+), 9 deletions(-) --- a/drivers/net/tap.c +++ b/drivers/net/tap.c @@ -716,10 +716,20 @@ static ssize_t tap_get_user(struct tap_q skb_reset_mac_header(skb); skb->protocol =3D eth_hdr(skb)->h_proto; =20 + rcu_read_lock(); + tap =3D rcu_dereference(q->tap); + if (!tap) { + kfree_skb(skb); + rcu_read_unlock(); + return total_len; + } + skb->dev =3D tap->dev; + if (vnet_hdr_len) { err =3D virtio_net_hdr_to_skb(skb, &vnet_hdr, tap_is_little_endian(q)); if (err) { + rcu_read_unlock(); drop_reason =3D SKB_DROP_REASON_DEV_HDR; goto err_kfree; } @@ -732,8 +742,6 @@ static ssize_t tap_get_user(struct tap_q __vlan_get_protocol(skb, skb->protocol, &depth) !=3D 0) skb_set_network_header(skb, depth); =20 - rcu_read_lock(); - tap =3D rcu_dereference(q->tap); /* copy skb_ubuf_info for callback when skb has no error */ if (zerocopy) { skb_zcopy_init(skb, msg_control); @@ -742,14 +750,8 @@ static ssize_t tap_get_user(struct tap_q uarg->callback(NULL, uarg, false); } =20 - if (tap) { - skb->dev =3D tap->dev; - dev_queue_xmit(skb); - } else { - kfree_skb(skb); - } + dev_queue_xmit(skb); rcu_read_unlock(); - return total_len; =20 err_kfree: