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Miller" , Jakub Kicinski , Paolo Abeni , netdev@vger.kernel.org, eric.dumazet@gmail.com, syzbot , Jiri Pirko Subject: Re: [PATCH net] netdevsim: avoid potential loop in nsim_dev_trap_report_work() Message-ID: References: <20240201175324.3752746-1-edumazet@google.com> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: Fri, Feb 02, 2024 at 01:39:26PM CET, edumazet@google.com wrote: >On Fri, Feb 2, 2024 at 1:04 PM Jiri Pirko wrote: >> >> Thu, Feb 01, 2024 at 06:53:24PM CET, edumazet@google.com wrote: >> >Many syzbot reports include the following trace [1] >> > >> >If nsim_dev_trap_report_work() can not grab the mutex, >> >it should rearm itself at least one jiffie later. >> > >> >[1] >> >Sending NMI from CPU 1 to CPUs 0: >> >NMI backtrace for cpu 0 >> >CPU: 0 PID: 32383 Comm: kworker/0:2 Not tainted 6.8.0-rc2-syzkaller-00031-g861c0981648f #0 >> >Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 11/17/2023 >> >Workqueue: events nsim_dev_trap_report_work >> > RIP: 0010:bytes_is_nonzero mm/kasan/generic.c:89 [inline] >> > RIP: 0010:memory_is_nonzero mm/kasan/generic.c:104 [inline] >> > RIP: 0010:memory_is_poisoned_n mm/kasan/generic.c:129 [inline] >> > RIP: 0010:memory_is_poisoned mm/kasan/generic.c:161 [inline] >> > RIP: 0010:check_region_inline mm/kasan/generic.c:180 [inline] >> > RIP: 0010:kasan_check_range+0x101/0x190 mm/kasan/generic.c:189 >> >Code: 07 49 39 d1 75 0a 45 3a 11 b8 01 00 00 00 7c 0b 44 89 c2 e8 21 ed ff ff 83 f0 01 5b 5d 41 5c c3 48 85 d2 74 4f 48 01 ea eb 09 <48> 83 c0 01 48 39 d0 74 41 80 38 00 74 f2 eb b6 41 bc 08 00 00 00 >> >RSP: 0018:ffffc90012dcf998 EFLAGS: 00000046 >> >RAX: fffffbfff258af1e RBX: fffffbfff258af1f RCX: ffffffff8168eda3 >> >RDX: fffffbfff258af1f RSI: 0000000000000004 RDI: ffffffff92c578f0 >> >RBP: fffffbfff258af1e R08: 0000000000000000 R09: fffffbfff258af1e >> >R10: ffffffff92c578f3 R11: ffffffff8acbcbc0 R12: 0000000000000002 >> >R13: ffff88806db38400 R14: 1ffff920025b9f42 R15: ffffffff92c578e8 >> >FS: 0000000000000000(0000) GS:ffff8880b9800000(0000) knlGS:0000000000000000 >> >CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 >> >CR2: 000000c00994e078 CR3: 000000002c250000 CR4: 00000000003506f0 >> >DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 >> >DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 >> >Call Trace: >> > >> > >> > >> > instrument_atomic_read include/linux/instrumented.h:68 [inline] >> > atomic_read include/linux/atomic/atomic-instrumented.h:32 [inline] >> > queued_spin_is_locked include/asm-generic/qspinlock.h:57 [inline] >> > debug_spin_unlock kernel/locking/spinlock_debug.c:101 [inline] >> > do_raw_spin_unlock+0x53/0x230 kernel/locking/spinlock_debug.c:141 >> > __raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:150 [inline] >> > _raw_spin_unlock_irqrestore+0x22/0x70 kernel/locking/spinlock.c:194 >> > debug_object_activate+0x349/0x540 lib/debugobjects.c:726 >> > debug_work_activate kernel/workqueue.c:578 [inline] >> > insert_work+0x30/0x230 kernel/workqueue.c:1650 >> > __queue_work+0x62e/0x11d0 kernel/workqueue.c:1802 >> > __queue_delayed_work+0x1bf/0x270 kernel/workqueue.c:1953 >> > queue_delayed_work_on+0x106/0x130 kernel/workqueue.c:1989 >> > queue_delayed_work include/linux/workqueue.h:563 [inline] >> > schedule_delayed_work include/linux/workqueue.h:677 [inline] >> > nsim_dev_trap_report_work+0x9c0/0xc80 drivers/net/netdevsim/dev.c:842 >> > process_one_work+0x886/0x15d0 kernel/workqueue.c:2633 >> > process_scheduled_works kernel/workqueue.c:2706 [inline] >> > worker_thread+0x8b9/0x1290 kernel/workqueue.c:2787 >> > kthread+0x2c6/0x3a0 kernel/kthread.c:388 >> > ret_from_fork+0x45/0x80 arch/x86/kernel/process.c:147 >> > ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:242 >> > >> >> What is actually the reason for this trace? I see that the RIP is on >> "start" pointer access in kasan code when instrument_atomic_read() >> is called on lock->val during spin_unlock checks. But why? > >This is a watchdog triggering because there are tasks stuck in D state. > > NMI backtrace for cpu 1 >CPU: 1 PID: 29 Comm: khungtaskd Not tainted >6.8.0-rc2-syzkaller-00031-g861c0981648f #0 >Hardware name: Google Google Compute Engine/Google Compute Engine, >BIOS Google 11/17/2023 >Call Trace: > >__dump_stack lib/dump_stack.c:88 [inline] >dump_stack_lvl+0xd9/0x1b0 lib/dump_stack.c:106 >nmi_cpu_backtrace+0x277/0x390 lib/nmi_backtrace.c:113 >nmi_trigger_cpumask_backtrace+0x299/0x300 lib/nmi_backtrace.c:62 >trigger_all_cpu_backtrace include/linux/nmi.h:160 [inline] >check_hung_uninterruptible_tasks kernel/hung_task.c:222 [inline] >watchdog+0xf87/0x1210 kernel/hung_task.c:379 >kthread+0x2c6/0x3a0 kernel/kthread.c:388 >ret_from_fork+0x45/0x80 arch/x86/kernel/process.c:147 >ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:242 > >Sending NMI from CPU 1 to CPUs 0: Ah, got it. Thanks!