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Thu, 29 Oct 2026 21:35:11 -0700 (PDT) Received: from amax.cluster.local ([115.233.223.43]) by smtp.gmail.com with ESMTPSA id 98e67ed59e1d1-3ae85f37e7esm934372a91.1.2026.10.29.21.35.08 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 29 Oct 2026 21:35:10 -0700 (PDT) From: l1za0.sec@gmail.com To: kuba@kernel.org Cc: andrew+netdev@lunn.ch, davem@davemloft.net, edumazet@kernel.org, pabeni@redhat.com, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, Haocheng Yu Subject: [BUG] WARNING in nsim_vlan_rx_add_vid Date: Fri, 30 Oct 2026 12:34:47 +0800 Message-Id: <20261030043447.3557387-1-l1za0.sec@gmail.com> X-Mailer: git-send-email 2.30.2 X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: Haocheng Yu Hi, We found a kernel warning in nsim_vlan_rx_add_vid() while fuzzing Linux with a modified version of syzkaller. We couldn't find a report of the same issue on syzbot. We are investigating the root cause and trying to develop a fix. Could you let us know whether this issue warrants a fix? The warning occurs on Linux 7.3.0-02415-g7be4bc52fd9e (#4, PREEMPT(full)) at drivers/net/netdevsim/netdev.c:569. The kernel then panics because panic_on_warn is set. The report also shows an existing SOFTLOCKUP taint; the relationship to this warning is not yet established. Relevant report excerpt: WARNING: drivers/net/netdevsim/netdev.c:569 at nsim_vlan_rx_add_vid+0xb5/0x120 Relevant stack trace (inline frames included): nsim_vlan_rx_add_vid (drivers/net/netdevsim/netdev.c:569) vlan_add_rx_filter_info (net/8021q/vlan_core.c:211) vlan_filter_push_vids (net/8021q/vlan_core.c:262) vlan_device_event (net/8021q/vlan.c:483) notifier_call_chain (kernel/notifier.c:85) call_netdevice_notifiers_info (net/core/dev.c:2260) __netdev_update_features (net/core/dev.c:11179) ethtool_set_features (net/ethtool/ioctl.c:155) dev_ethtool_locked (net/ethtool/ioctl.c:3488) dev_ethtool (net/ethtool/ioctl.c:3669) dev_ioctl (net/core/dev_ioctl.c:745) sock_do_ioctl (net/socket.c:1339) sock_ioctl (net/socket.c:1446) __x64_sys_ioctl (fs/ioctl.c:583) The syzkaller reproducer opens CAN J1939 sockets and issues two SIOCETHTOOL ioctls with ETHTOOL_SFEATURES requests for netdevsim0. The warning is reached through the VLAN receive-filter update path when network device features are updated. The root cause has not yet been confirmed. Full syzkaller reproducer: # {Threaded:false Repeat:true RepeatTimes:0 Procs:1 Slowdown:1 Sandbox:none SandboxArg:0 Leak:false NetInjection:false NetDevices:true NetReset:false Cgroups:false BinfmtMisc:false CloseFDs:true KCSAN:false DevlinkPCI:false NicVF:false USB:false VhciInjection:false Wifi:false IEEE802154:false Sysctl:false Swap:false UseTmpDir:false HandleSegv:false Trace:false CallComments:true LegacyOptions:{Collide:false Fault:false FaultCall:0 FaultNth:0}} r0 = socket$can_j1939(0x1d, 0x2, 0x7) ioctl$sock_SIOCETHTOOL(r0, 0x8946, &(0x7f0000000080)={'netdevsim0\x00', &(0x7f0000000040)=@ethtool_sfeatures={0x3b, 0x2, [{0x25a, 0xfffffffd}, {0xffff8000, 0x2}]}}) socket$can_j1939(0x1d, 0x2, 0x7) r1 = socket$can_j1939(0x1d, 0x2, 0x7) ioctl$sock_SIOCETHTOOL(r1, 0x8946, &(0x7f0000000080)={'netdevsim0\x00', &(0x7f0000000040)=@ethtool_sfeatures={0x3b, 0x2, [{0x25a, 0x1}, {0xffff8000, 0xffffffff}]}}) Best regards, Haocheng Yu