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Thu, 30 Jul 2026 01:22:42 -0700 (PDT) Received: from ala-exchng01.corp.ad.wrs.com (10.11.224.121) by ala-exchng01.corp.ad.wrs.com (10.11.224.121) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2507.61; Thu, 30 Jul 2026 01:22:41 -0700 Received: from pek-yzhou-d3.wrs.com (10.11.232.110) by ala-exchng01.corp.ad.wrs.com (10.11.224.121) with Microsoft SMTP Server id 15.1.2507.61 via Frontend Transport; Thu, 30 Jul 2026 01:22:39 -0700 From: Yun Zhou To: , , , , , , CC: , , Subject: [PATCH net v3] net: erspan: set lltx to avoid sch_direct_xmit deadlock Date: Thu, 30 Jul 2026 16:22:38 +0800 Message-ID: <20260730082238.676845-1-yun.zhou@windriver.com> X-Mailer: git-send-email 2.43.0 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Content-Type: text/plain X-Authority-Analysis: v=2.4 cv=ZMznX37b c=1 sm=1 tr=0 ts=6a6b09d2 cx=c_pps a=AbJuCvi4Y3V6hpbCNWx0WA==:117 a=AbJuCvi4Y3V6hpbCNWx0WA==:17 a=RAioF0-LDSMA:10 a=VkNPw1HP01LnGYTKEx00:22 a=bi6dqmuHe4P4UrxVR6um:22 a=iKiJcTA2PjBS6x5JeXcw:22 a=edf1wS77AAAA:8 a=hSkVLCK3AAAA:8 a=VwQbUJbxAAAA:8 a=t7CeM3EgAAAA:8 a=ADlydbMj1Wbzk9vhUvkA:9 a=DcSpbTIhAlouE1Uv7lRv:22 a=cQPPKAXgyycSBL8etih5:22 a=FdTzh2GWekK77mhwV6Dw:22 X-Proofpoint-Spam-Info: AW1haW4tMjYwNzMwMDA1OSBTYWx0ZWRfX56AqZ4wZab3U Il29Z9Ydn+hJzi0+p2M6hNRcKDZN+Nq/C3gw/QMjUCDbo3+w/NLdgPpTQanViyKXZUN579kJA4q Dw0G0BLhCBartdaIYC7lRocYipYnAo/kR6IAGi2hV9UHQeaZ6AGB X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwNzMwMDA1OSBTYWx0ZWRfX/6yaJZyJgbCh FOU+dl4SjDAbN8seP7lkwdW2jZjzGteddnpaKj9uEtBQJUeoUZ83eLzn2I6wopP/7ee8bQ6NyZV 6+FYCw11mYdMw1FhrtjN362la4Sg+qcLfkurojIYTlKbEeX+w6U7TgD12AwJW+sLcLsXo8mhk5M yu/PVyYjqDTT9TNeIKZ66CQom1VIT15a+IGED/DSI2tIwnJgrS4hWmUOpHaJBaCv2kJwEgZgtR0 9U6RzJuGKKdtjYGhyYau47K6UfUzjefs8pvXIJwfJJ8r2BxuuuDzb0SQnvKygL8G2dbAnKAwilR ZDl8d1ZWHFmfv8DC5dRwJbRJawcEP4HZyVtuyEiW92d5068Pkx3KIsai8UIvU8jBaRxCTl5SEA1 a1C7lmXTY/d6EukITQCJRA3/V9mCVtpZRX5A7nK+9lpHKrULmmGY43JOwFBMtsXb60SCtKhfG/t Psm5qYUslHr0Is2KZ7w== X-Proofpoint-ORIG-GUID: iRy2sgmZ4zfJ3R-AIpFE9_bNgwGJ23Um X-Proofpoint-GUID: iRy2sgmZ4zfJ3R-AIpFE9_bNgwGJ23Um 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=2026-07-30_02,2026-07-29_01,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 bulkscore=0 malwarescore=0 clxscore=1015 lowpriorityscore=0 spamscore=0 adultscore=0 suspectscore=0 impostorscore=0 phishscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2606150000 definitions=main-2607300059 erspan_xmit() re-enters the network stack via ip_tunnel_xmit(), causing nested acquisition of _xmit_lock on the underlay device while already holding the ERSPAN device's _xmit_lock. Both are ARPHRD_ETHER and share the same lockdep class, creating an ABBA deadlock: sch_direct_xmit [lock erspan] -> erspan_xmit -> ip_tunnel_xmit -> ip_output -> __dev_queue_xmit -> sch_direct_xmit [lock underlay] Set dev->lltx = true so HARD_TX_LOCK() skips the spinlock for ERSPAN. This is safe as erspan_xmit() has no shared mutable state: o_seqno is atomic, stats use atomic_long_inc, and dst_cache is per-CPU. GRETAP, the sibling device with identical xmit structure, already sets lltx. Closes: https://syzkaller.appspot.com/bug?extid=9bda1b9fbb7fbdf9b62b Reported-by: syzbot+9bda1b9fbb7fbdf9b62b@syzkaller.appspotmail.com Fixes: 84e54fe0a5ea ("gre: introduce native tunnel support for ERSPAN") Fixes: 5a963eb61b7c ("ip6_gre: Add ERSPAN native tunnel support") Cc: stable@vger.kernel.org Signed-off-by: Yun Zhou --- v3: - add fix for IPv6 v2: - change subject prefix to [PATCH net] net/ipv4/ip_gre.c | 2 ++ net/ipv6/ip6_gre.c | 2 ++ 2 files changed, 4 insertions(+) diff --git a/net/ipv4/ip_gre.c b/net/ipv4/ip_gre.c index 0ba1e94e9012..8c5ad8ec8d09 100644 --- a/net/ipv4/ip_gre.c +++ b/net/ipv4/ip_gre.c @@ -1363,6 +1363,8 @@ static int erspan_tunnel_init(struct net_device *dev) dev->features |= GRE_FEATURES; dev->hw_features |= GRE_FEATURES; dev->priv_flags |= IFF_LIVE_ADDR_CHANGE; + /* Skip TX lock: xmit re-enters stack, risking ABBA with underlay */ + dev->lltx = true; netif_keep_dst(dev); return ip_tunnel_init(dev); diff --git a/net/ipv6/ip6_gre.c b/net/ipv6/ip6_gre.c index b843116e9b70..143166e3e586 100644 --- a/net/ipv6/ip6_gre.c +++ b/net/ipv6/ip6_gre.c @@ -1870,6 +1870,8 @@ static int ip6erspan_tap_init(struct net_device *dev) dev->mtu -= 8; dev->priv_flags |= IFF_LIVE_ADDR_CHANGE; + /* Skip TX lock: xmit re-enters stack, risking ABBA with underlay */ + dev->lltx = true; ip6erspan_tnl_link_config(tunnel, 1); netdev_hold(dev, &tunnel->dev_tracker, GFP_KERNEL); -- 2.43.0