From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-oi1-f197.google.com (mail-oi1-f197.google.com [209.85.167.197]) (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 E76E33EE1E0 for ; Fri, 7 Aug 2026 09:21:35 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.167.197 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1786094498; cv=none; b=ObzOk9MrrD9+RJft/yoxGW3NjjHzwhRNVZXReWuDbXFDqQmxuoEqGf/aDPynM02pN6JpSMg7quo7XWOzK5hk6sLvf4kIvtJvGQG/NNzTHh3tGXcv6TBz/Q2pC5cpoXcMyUPxiwNHkm7RInl69KqsH++59rvd2Ph+Fh/54v6ww+0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1786094498; c=relaxed/simple; bh=X0t/MAcZpTNODHUjtSRgs7rJrIqj7xNlQX5YtnbWaWo=; h=MIME-Version:Date:In-Reply-To:Message-ID:Subject:From:To: Content-Type; b=h0Y3sRc+2Zcf4NxdW7Ew/I7expauWjAAaum8IqQyaUouL/AKd8i0B4NQyEQABVQLvd6bp3wxJVfWEhvUqC0giDXcUFhH8bIQ4fQaAirY+bBZvhksrB5K3KH0xed52A5ZNorxTmcoD3yjJWcBF/0EsTNZkV2n9FRtPSxi1xNBGOs= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=fail (p=none dis=none) header.from=syzkaller.appspotmail.com; spf=pass smtp.mailfrom=M3KW2WVRGUFZ5GODRSRYTGD7.apphosting.bounces.google.com; arc=none smtp.client-ip=209.85.167.197 Authentication-Results: smtp.subspace.kernel.org; dmarc=fail (p=none dis=none) header.from=syzkaller.appspotmail.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=M3KW2WVRGUFZ5GODRSRYTGD7.apphosting.bounces.google.com Received: by mail-oi1-f197.google.com with SMTP id 5614622812f47-4ab4ca7ce3fso2825832b6e.0 for ; Fri, 07 Aug 2026 02:21:35 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1786094494; x=1786699294; h=content-type:to:from:subject:message-id:in-reply-to:date :mime-version:x-gm-message-state:from:to:cc:subject:date:message-id :reply-to:content-type; bh=1w1bzy8ztEMz76rKTp6YTKy70X4mXB83RhI3ZGRktQI=; b=sGi1k6pilHFT6BzxB8091/99LKoSpTigbshuEnGTuMd1IrW4rMIaWTf5TjL8e9yBuU yPD28gNxGbTwJa6VaRld308eOCsmjAHI/E6gY+H56d4doZlmIzY61HMyxj8Wf27fEQd/ crmr3FnvFIHmCRYYTpLkH2iJnnuM3TJkiA0mhtjCH/WTS8RMOK5bCH/bp6cTAYP+Bka2 yX1+hzya9uBiGO4avEOPDChOnPKszoi778QMYPympTnnB7edo236DCGZH3fmlxFIgzEM 1wraddLt9dsoDpdljtyM6sNmAzSseMPRhh1acZGnwoTnq/xCxECbkol28XM7Yrvp103d u/cw== X-Forwarded-Encrypted: i=1; AHgh+RoGVg5gayw8BxWR7U5MDnRIrfDc26cftDYwpkx9ULdgY53SOmPQ0fzJ/c1aBdbNZrntqLynK2xpo7keqLQ=@vger.kernel.org X-Gm-Message-State: AOJu0YwT7+I49f1HyZDEmh/4XFghblBtEKIaPpa/EyAtIsk/WEK0xnPT lhp1QabqrSnmLzhZLm90Uw1d9jMv5FvZvafrDm15nl2c+ew9m8BC8BvEb1gLbKaGn1o+PJI1TWu lffR3eZWrjg6XnXMFgsQoYY87mByufhE/HU1VDV1Ltz8tD5KK2iJHN8gvH6U= Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Received: by 2002:a05:6808:c1f3:b0:496:10e6:f76e with SMTP id 5614622812f47-4afadf21ab6mr12718158b6e.4.1786094494766; Fri, 07 Aug 2026 02:21:34 -0700 (PDT) Date: Fri, 07 Aug 2026 02:21:34 -0700 In-Reply-To: <682ffdaa.a70a0220.253bc2.0061.GAE@google.com> X-Google-Appengine-App-Id: s~syzkaller X-Google-Appengine-App-Id-Alias: syzkaller Message-ID: <6a75a39e.01d0871a.3a0d52.0042.GAE@google.com> Subject: Re: [syzbot] [kernfs?] [ext4?] INFO: task hung in sb_start_write (2) From: syzbot To: brauner@kernel.org, cem@kernel.org, gregkh@linuxfoundation.org, jack@suse.cz, jfs-discussion@lists.sourceforge.net, kent.overstreet@linux.dev, linux-bcachefs@vger.kernel.org, linux-ext4@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-xfs@vger.kernel.org, shaggy@kernel.org, syzkaller-bugs@googlegroups.com, tj@kernel.org, viro@zeniv.linux.org.uk Content-Type: text/plain; charset="UTF-8" syzbot has found a reproducer for the following issue on: HEAD commit: f9a2394a2348 Merge tag 'mm-hotfixes-stable-2026-08-06-18-4.. git tree: upstream console output: https://syzkaller.appspot.com/x/log.txt?x=1379cfb9580000 kernel config: https://syzkaller.appspot.com/x/.config?x=98da55a882774dfe dashboard link: https://syzkaller.appspot.com/bug?extid=b3fba2e269970207b61d compiler: Debian clang version 22.1.8 (++20260613092233+e80beda6e255-1~exp1~20260613092250.77), Debian LLD 22.1.8 C reproducer: https://syzkaller.appspot.com/x/repro.c?x=14b9d7b9580000 IMPORTANT: if you fix the issue, please add the following tag to the commit: Reported-by: syzbot+b3fba2e269970207b61d@syzkaller.appspotmail.com INFO: task syz-executor328:5959 blocked for more than 15 seconds. Not tainted syzkaller #0 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. task:syz-executor328 state:D stack:28328 pid:5959 tgid:5959 ppid:5947 task_flags:0x400040 flags:0x00080000 Call Trace: context_switch kernel/sched/core.c:5510 [inline] __schedule+0x16dc/0x5500 kernel/sched/core.c:7234 __schedule_loop kernel/sched/core.c:7311 [inline] schedule+0x164/0x2b0 kernel/sched/core.c:7326 percpu_rwsem_wait+0x32d/0x4a0 kernel/locking/percpu-rwsem.c:164 __percpu_down_read+0xf8/0x140 kernel/locking/percpu-rwsem.c:180 percpu_down_read_internal include/linux/percpu-rwsem.h:67 [inline] percpu_down_read_freezable include/linux/percpu-rwsem.h:83 [inline] __sb_start_write include/linux/fs/super.h:19 [inline] sb_start_write+0x18e/0x1c0 include/linux/fs/super.h:125 mnt_want_write+0x41/0x90 fs/namespace.c:494 do_tmpfile+0x6c/0x240 fs/namei.c:4817 path_openat+0x3095/0x3850 fs/namei.c:4854 do_file_open+0x23e/0x4a0 fs/namei.c:4892 do_sys_openat2+0x115/0x200 fs/open.c:1368 do_sys_open fs/open.c:1374 [inline] __do_sys_openat fs/open.c:1390 [inline] __se_sys_openat fs/open.c:1385 [inline] __x64_sys_openat+0x138/0x170 fs/open.c:1385 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0x174/0x580 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7f3fb490aaf7 RSP: 002b:00007fff7f2f6f10 EFLAGS: 00000202 ORIG_RAX: 0000000000000101 RAX: ffffffffffffffda RBX: 0000555578a51400 RCX: 00007f3fb490aaf7 RDX: 0000000000410001 RSI: 00007f3fb494a764 RDI: ffffffffffffff9c RBP: 00007f3fb494a764 R08: 0000000000000000 R09: 0000000000000000 R10: 00000000000001b6 R11: 0000000000000202 R12: 00007fff7f2f70d8 R13: 0000000000000002 R14: 00007f3fb4970c80 R15: 0000000000000002 Showing all locks held in the system: 1 lock held by khungtaskd/38: #0: ffffffff8e1c3000 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:300 [inline] #0: ffffffff8e1c3000 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:840 [inline] #0: ffffffff8e1c3000 (rcu_read_lock){....}-{1:3}, at: debug_show_all_locks+0x2e/0x180 kernel/locking/lockdep.c:6775 2 locks held by getty/5356: #0: ffff88803688d0a0 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x25/0x70 drivers/tty/tty_ldisc.c:243 #1: ffffc90003cc62e0 (&ldata->atomic_read_lock){+.+.}-{4:4}, at: n_tty_read+0x460/0x1360 drivers/tty/n_tty.c:2211 1 lock held by syz-executor328/5959: #0: ffff888035a88500 (sb_writers#4){++++}-{0:0}, at: mnt_want_write+0x41/0x90 fs/namespace.c:494 ============================================= NMI backtrace for cpu 1 CPU: 1 UID: 0 PID: 38 Comm: khungtaskd Not tainted syzkaller #0 PREEMPT_{RT,(full)} Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026 Call Trace: dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120 nmi_cpu_backtrace+0x274/0x2d0 lib/nmi_backtrace.c:122 nmi_trigger_cpumask_backtrace+0x17a/0x380 lib/nmi_backtrace.c:65 trigger_all_cpu_backtrace include/linux/nmi.h:162 [inline] __sys_info lib/sys_info.c:157 [inline] sys_info+0x135/0x170 lib/sys_info.c:165 check_hung_uninterruptible_tasks kernel/hung_task.c:353 [inline] watchdog+0xfd7/0x1030 kernel/hung_task.c:561 kthread+0x388/0x470 kernel/kthread.c:436 ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245 Sending NMI from CPU 1 to CPUs 0: NMI backtrace for cpu 0 CPU: 0 UID: 0 PID: 0 Comm: swapper/0 Not tainted syzkaller #0 PREEMPT_{RT,(full)} Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026 RIP: 0010:pv_native_safe_halt+0xf/0x20 arch/x86/kernel/paravirt.c:64 Code: cb 6e 02 e9 13 cf 03 00 cc cc cc 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 f3 0f 1e fa 66 90 0f 00 2d 33 44 24 00 fb f4 cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc 90 90 90 90 90 RSP: 0018:ffffffff8de07de0 EFLAGS: 00000242 RAX: 000000000009a1e9 RBX: ffffffff81998590 RCX: 0000000080000001 RDX: 0000000000000001 RSI: ffffffff8d887e30 RDI: ffffffff8bca6d80 RBP: ffffffff8de07eb8 R08: ffff8880b8633d5b R09: 1ffff110170c67ab R10: dffffc0000000000 R11: ffffed10170c67ac R12: 0000000000000000 R13: 1ffffffff1bdede8 R14: 1ffffffff1bc0fc4 R15: dffffc0000000000 FS: 0000000000000000(0000) GS:ffff888125c36000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000563216b981d0 CR3: 000000000dfb0000 CR4: 00000000003526f0 Call Trace: arch_safe_halt arch/x86/kernel/process.c:767 [inline] default_idle+0x9/0x20 arch/x86/kernel/process.c:768 default_idle_call+0x72/0xb0 kernel/sched/idle.c:122 cpuidle_idle_call kernel/sched/idle.c:199 [inline] do_idle+0x2e0/0x540 kernel/sched/idle.c:355 cpu_startup_entry+0x43/0x60 kernel/sched/idle.c:454 rest_init+0x2de/0x300 init/main.c:717 start_kernel+0x392/0x3e0 init/main.c:1175 x86_64_start_reservations+0x24/0x30 arch/x86/kernel/head64.c:310 x86_64_start_kernel+0x137/0x1b0 arch/x86/kernel/head64.c:291 common_startup_64+0x13e/0x157 --- If you want syzbot to run the reproducer, reply with: #syz test: git://repo/address.git branch-or-commit-hash If you attach or paste a git patch, syzbot will apply it before testing.