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Sun, 02 Aug 2026 22:48:47 +0000 (GMT) Received: from pps.filterd (phxpaimrmta03.imrmtpd1.prodappphxaev1.oraclevcn.com [127.0.0.1]) by phxpaimrmta03.imrmtpd1.prodappphxaev1.oraclevcn.com (8.18.1.7/8.18.1.7) with ESMTP id 672Mj3vV040203; Sun, 2 Aug 2026 22:48:46 GMT Received: from pps.reinject (localhost [127.0.0.1]) by phxpaimrmta03.imrmtpd1.prodappphxaev1.oraclevcn.com (PPS) with ESMTPS id 4fs78a1q7v-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Sun, 02 Aug 2026 22:48:46 +0000 (GMT) Received: from phxpaimrmta03.imrmtpd1.prodappphxaev1.oraclevcn.com (phxpaimrmta03.imrmtpd1.prodappphxaev1.oraclevcn.com [127.0.0.1]) by pps.reinject (8.18.1.12/8.18.1.12) with ESMTP id 672MmkXI005444; Sun, 2 Aug 2026 22:48:46 GMT Received: from localhost.localdomain (ca-dev80.us.oracle.com [10.211.9.80]) by phxpaimrmta03.imrmtpd1.prodappphxaev1.oraclevcn.com (PPS) with ESMTP id 4fs78a1q7p-1; Sun, 02 Aug 2026 22:48:46 +0000 (GMT) From: Dongli Zhang To: netdev@vger.kernel.org Cc: willemdebruijn.kernel@gmail.com, jasowangio@gmail.com, andrew+netdev@lunn.ch, davem@davemloft.net, edumazet@google.com, kuba@kernel.org, pabeni@redhat.com, mst@redhat.com, denis.pilipchuk@oracle.com, joe.jin@oracle.com Subject: [PATCH 1/1] net: tap: set skb->dev before parsing virtio net header in tap_get_user_xdp() Date: Sun, 2 Aug 2026 15:46:12 -0700 Message-ID: <20260802224612.264563-1-dongli.zhang@oracle.com> X-Mailer: git-send-email 2.43.5 Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1143,Hydra:6.1.134,FMLib:17.12.100.49 definitions=2026-08-02_06,2026-07-30_01,2025-10-01_01 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 phishscore=0 lowpriorityscore=0 suspectscore=0 adultscore=0 mlxscore=0 bulkscore=0 spamscore=0 malwarescore=0 mlxlogscore=999 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.19.0-2606160000 definitions=main-2608020210 X-Proofpoint-ORIG-GUID: 2vSFbHLr3oSNFkbFc-I-TmnDQHNXHaON X-Authority-Analysis: v=2.4 cv=XqnK/1F9 c=1 sm=1 tr=0 ts=6a6fc950 b=1 cx=c_pps a=WeWmnZmh0fydH62SvGsd2A==:117 a=WeWmnZmh0fydH62SvGsd2A==:17 a=Sv0fKeRqtYgA:10 a=VkNPw1HP01LnGYTKEx00:22 a=jiCTI4zE5U7BLdzWsZGv:22 a=BqU2WV_vvsyTyxaotp0D:22 a=VwQbUJbxAAAA:8 a=yPCof4ZbAAAA:8 a=qR_b30O-rng5yiWcDyYA:9 a=WmVTiCyuxqgg3mnwYu6p:22 X-Proofpoint-Spam-Info: AW1haW4tMjYwODAyMDIxMSBTYWx0ZWRfX9IawLD5qvKkl CzSSLjgJvke/a043XhqHO4VusT0AaDne578TYFx0/rYuYjOKmDpWPVKDETDxpazX/99XiHc4n3a +E3wP/F8CCUjYM5e/L1fy4LWxWyh5EKqFYb9blyXn67DBWIzAWJE X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwODAyMDIxMSBTYWx0ZWRfX2TwYJHt+48Kk ETHpHn6hs9YA52IhTWkeLw9l4tx/Xfvq68t/sxgVF9K2loX81nD5cZqoKN3OkkCFjAfmJXHMib7 hieVm72TtSZZpGSqBtblV8PpYyWIFu7rgYJhz9dtg9lEPc+dfZuE8EP6BwKlXonoq2ziGjgFma3 Kh4SiGJ27n0ESYxjWY6L0t5qJulcFHJ4+6L/WMda4gJKWCSo5FiAZrckUSXwNEWmgKdxz0CQ3C/ v9kTf1KgfztvsFznMVzb4CjfekLKZ6cQY9q6UGbWIyhvMumNmbEee6xS5FgsK03dhzXf7omrBv9 vQ22eAxHMPmtlEpzeIScdVHsB1LBOfs3bvMWZs7yByVJWxJkfJq2/h07915OK55WnIKYVhu3a/X qInRiG95yAiy2HaEOl9Jz2gF2UUb5AhTJzp1Db4uel0NhLP6nsEEIFNCyBlNkNxe1I43cmiT/PT NHX/39UdnpWZ33xgjqw== X-Proofpoint-GUID: 2vSFbHLr3oSNFkbFc-I-TmnDQHNXHaON The commit 4f61f133f354 ("net: tap: NULL pointer derefence in dev_parse_header_protocol when skb->dev is null") fixed a crash in tap_get_user() by assigning skb->dev before calling tun_vnet_hdr_to_skb(). This is required because virtio_net_hdr_to_skb() may invoke dev_parse_header_protocol(), which dereferences skb->dev. Without the assignment, a NULL pointer dereference can occur. However, tap_get_user_xdp() still parses the virtio-net header before assigning skb->dev. When the vhost TX path passes an XDP buffer containing a GSO virtio-net header but the protocol is set to zero on purpose, tun_vnet_hdr_to_skb() can reach dev_parse_header_protocol() while skb->dev is still NULL, resulting in a crash. Fix this by looking up the tap device and assigning skb->dev before calling tun_vnet_hdr_to_skb(), matching the ordering already used in tap_get_user(). Preserve the existing RCU read-side critical section across dev_queue_xmit(). Fixes: 924a9bc362a5 ("net: check if protocol extracted by virtio_net_hdr_set_proto is correct") Cc: stable@vger.kernel.org Assisted-by: Codex:GPT-5.5 Signed-off-by: Dongli Zhang --- drivers/net/tap.c | 24 ++++++++++++++---------- 1 file changed, 14 insertions(+), 10 deletions(-) diff --git a/drivers/net/tap.c b/drivers/net/tap.c index fae115915c8e..5d2d34d24ce8 100644 --- a/drivers/net/tap.c +++ b/drivers/net/tap.c @@ -1074,10 +1074,21 @@ static int tap_get_user_xdp(struct tap_queue *q, struct xdp_buff *xdp) skb_reset_mac_header(skb); skb->protocol = eth_hdr(skb)->h_proto; + rcu_read_lock(); + tap = rcu_dereference(q->tap); + if (!tap) { + kfree_skb(skb); + rcu_read_unlock(); + return 0; + } + skb->dev = tap->dev; + if (vnet_hdr_len) { err = tun_vnet_hdr_to_skb(q->flags, skb, gso); - if (err) + if (err) { + rcu_read_unlock(); goto err_kfree; + } } /* Move network header to the right position for VLAN tagged packets */ @@ -1085,15 +1096,8 @@ static int tap_get_user_xdp(struct tap_queue *q, struct xdp_buff *xdp) vlan_get_protocol_and_depth(skb, skb->protocol, &depth) != 0) skb_set_network_header(skb, depth); - rcu_read_lock(); - tap = rcu_dereference(q->tap); - if (tap) { - skb->dev = tap->dev; - skb_probe_transport_header(skb); - dev_queue_xmit(skb); - } else { - kfree_skb(skb); - } + skb_probe_transport_header(skb); + dev_queue_xmit(skb); rcu_read_unlock(); return 0; -- 2.43.5