From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-ua1-f43.google.com (mail-ua1-f43.google.com [209.85.222.43]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 6CA3D22127C; Wed, 16 Jul 2025 09:23:44 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.222.43 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1752657825; cv=none; b=HXJU/oEzu/m49cIqfy+vWZFBNYiB+myUZ8NUCq6v1kluzR35s07RyxR+Odk50Mnl/UpL9jU1RPpE0Olk7jWBFWZCXyeypwGeN5JkixERNNR5t6hy6afHtqSBKY0UpoibqMkJGU5HwHYhQGcvGVOzpFGyKnzeJhzMihYAtKzbxAA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1752657825; c=relaxed/simple; bh=8bb59Y7qB/JB1/x9ope6S0w9QIQuBIWcCUed5RbRWdI=; h=MIME-Version:From:Date:Message-ID:Subject:To:Cc:Content-Type; b=F+AbB0KTxx52ej3W9tQ1DhfkWLUcyWgeqn0T8V3egeWRpUC4cm6xdY/wj3VLtypEkwNJ7LI/49eox7xa0u7b+upjJ8ZfS6QjOb/TrEQGKOhjsVDTogQYZJrHCM4IZkkUaRLCSqyNQp60NMudAdxp/NEVYrAAwInwsaIYOBIC4MQ= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com; spf=pass smtp.mailfrom=gmail.com; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b=A96Y+yss; arc=none smtp.client-ip=209.85.222.43 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=gmail.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="A96Y+yss" Received: by mail-ua1-f43.google.com with SMTP id a1e0cc1a2514c-88173565536so670427241.0; Wed, 16 Jul 2025 02:23:44 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20230601; t=1752657823; x=1753262623; darn=vger.kernel.org; h=cc:to:subject:message-id:date:from:mime-version:from:to:cc:subject :date:message-id:reply-to; bh=8bb59Y7qB/JB1/x9ope6S0w9QIQuBIWcCUed5RbRWdI=; b=A96Y+yssh8lylf7PdrmBqHZjYOVs4Dzi4mP2PoULJhHSrR/idSvoWQzUbhfGyHUVyM sclrtRX6vLXO2JkJKXQFrUnFS1pe27l81XdIlJNzw1eqdSPA3kr60HY2fQNqyMLuGLt5 t29S1ubBNHdHkxskjnQB+ugq+iaXWADBZA7AZyHrgJSKv6YEFzQeUak8f8T0FFka0RBw +Tq/du7/paCXLSKPOrg2yualGaFPZzkXUFfcj2QNkjsS2sh1p+atL7AY+KeTDi/0WyTT JuEU5pJIlpwFIt8Jo4fo8eHUGXnjLZzMbNxNkZlVZ6gNOcHmDwrhzlvDcGH3EuPeFLZA kmyg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1752657823; x=1753262623; h=cc:to:subject:message-id:date:from:mime-version:x-gm-message-state :from:to:cc:subject:date:message-id:reply-to; bh=8bb59Y7qB/JB1/x9ope6S0w9QIQuBIWcCUed5RbRWdI=; b=vT8kAMRpbFV8ANN/abv6d0MirtwDUzOt3wAVmpK3eSYdADopD42dFrzAXyI1k5OO1O S7af9otiVK86ZmU3oaISwB4807pv27wVqbuvBbTHrCJjq1B039w1zVJosJFnYMxtGn2m NuWQ/7AxIOwEyfW9NNmEUbubB6Zbog7h9VxKZGGKYVqPBV3p/jeVWCyu0d8eY8LJAD14 QzrIXeVf1jVyKyTQuLvt7vuIJFztORCmrbyIS/D3rkxfo/9HoEzb0yJggbb8PIa3dtkJ zdhzhKPfJlKScLSw5qPuuRp4ZI/OM0GaAUpAF0NRNcQdMoGksM34p2e5PykgPpz7IgUS qcmA== X-Forwarded-Encrypted: i=1; AJvYcCU3D060rOp26/EgkyOateZcRXz2OK6liJm+zo93PvFnNcXUzBa4Ikpxmk7Yy9bOoJY3z+5xb5cI@vger.kernel.org, AJvYcCUbNYjWMIlw7ywSG0p7kpJV5waU13+WcIkPwLJ2mVjpbuP2BuNcJmWyGeIw5o8Suu5KnGc3Vgueeu5vVoU=@vger.kernel.org X-Gm-Message-State: AOJu0YxHmLbyLz87yvlMUwOOtyS7WE6HrG5Yw75avHHXxXGURcDFF3CS upppr8rcQe4NPf0aQ3Nvamn6FubjEvS/+VfrcwPM8xLz5SGDwFUf/4fwWB0DlUeo8efitN0dLO0 GU2c9/KagTxVx/ybtpY8cRAUH7EuVR9z3qXExSbyiEA== X-Gm-Gg: ASbGncv4+rDtgvmdeojtFWu5CQV/ouzJ/7RIwBUwviqlYbBb3dVEEx61gaW6DN/4HQD yDBXOW5quBVhaSlJqYoj92BMmCGmucfnkEYZAzzhp5Qdg+YJejd3YqSvhNQ+QBkPpbdJEHHElrm ls1CAKOeQeYSS0R8+OeuiapH4jSzu9PH+ayIALurqsJyeKSZZo66dtwiJ9ecFoncxx0f6ZhrLXr hb3w7U= X-Google-Smtp-Source: AGHT+IHbhfnfusQK9pbbtL026/fcLsRE78Jlhv++1FuiMatxhLTQJ+73q9kklmr2eP6jxQDehdPv2C7LAS1LRoealqE= X-Received: by 2002:a05:6102:3e11:b0:4e7:866c:5cd9 with SMTP id ada2fe7eead31-4f890152c29mr1304099137.11.1752657823234; Wed, 16 Jul 2025 02:23:43 -0700 (PDT) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 From: Xianying Wang Date: Wed, 16 Jul 2025 17:23:29 +0800 X-Gm-Features: Ac12FXyNFIaCK2pDYZ0jchMpDYF8x-Rd4WuhffoKeJLrRhYKDwWu0ZHWBZNeFqg Message-ID: Subject: [BUG] INFO: rcu detected stall in unix_stream_connect To: kuniyu@google.com Cc: davem@davemloft.net, edumazet@google.com, kuba@kernel.org, pabeni@redhat.com, horms@kernel.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org Content-Type: text/plain; charset="UTF-8" Hi, I discovered a kernel panic using the Syzkaller framework, described as INFO: rcu detected stall. This issue was reproduced on kernel version 6.16.0-rc5. >From the dmesg log, RCU detects a stall on CPU 0. The NMI backtrace, which shows what the CPU was actually doing, reveals it was stuck in a tight loop within the timer interrupt handler. The CPU appears to be spinning in functions like lapic_next_deadline (arch/x86/kernel/apic/apic.c:429) while processing a timer softirq in run_timer_softirq (kernel/time/timer.c:2403). Meanwhile, the task that was running on CPU 0 before it got stuck in the interrupt is blocked in the unix_stream_connect function (net/unix/af_unix.c:1683). The syzkaller reproducer appears to create a deadlock scenario by having a listening UNIX socket attempt to connect to its own endpoint. I suspect this is a complex race condition or deadlock within the kernel's core timer subsystem. The stress and unusual blocking state induced by the UNIX socket operations, combined with concurrent POSIX timer usage, likely exposes a latent bug in the hrtimer or tick management. This causes the CPU to spin with interrupts disabled, which in turn triggers the RCU stall. This can be reproduced on: HEAD commit: d7b8f8e20813f0179d8ef519541a3527e7661d3a report: https://pastebin.com/raw/N3GD5hL7 console output : https://pastebin.com/raw/RCZfTKCb kernel config : https://pastebin.com/raw/xAVw5DnH C reproducer :https://pastebin.com/raw/Z1B1ray5 Let me know if you need more details or testing. Best regards, Xianying