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2002:a05:6808:c197:b0:4b3:89ae:df60 with SMTP id 5614622812f47-4b398342e94mr17578034b6e.16.1788036984074; Sat, 29 Aug 2026 13:56:24 -0700 (PDT) Date: Sat, 29 Aug 2026 13:56:24 -0700 In-Reply-To: <695aefde.050a0220.1c9965.001c.GAE@google.com> X-Google-Appengine-App-Id: s~syzkaller X-Google-Appengine-App-Id-Alias: syzkaller Message-ID: <6a934778.4d659fcc.734b4.002f.GAE@google.com> Subject: Re: [syzbot] [mm?] INFO: rcu detected stall in __mmap_complete From: syzbot To: akpm@linux-foundation.org, dvyukov@google.com, elver@google.com, glider@google.com, jannh@google.com, kasan-dev@googlegroups.com, liam.howlett@oracle.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org, lorenzo.stoakes@oracle.com, netdev@vger.kernel.org, pfalcato@suse.de, syzkaller-bugs@googlegroups.com, vbabka@suse.cz Content-Type: text/plain; charset="UTF-8" syzbot has found a reproducer for the following issue on: HEAD commit: 1b78070aaef6 Merge tag 'net-7.3-rc1' of git://git.kernel.o.. git tree: net-next console output: https://syzkaller.appspot.com/x/log.txt?x=154d7d49580000 kernel config: https://syzkaller.appspot.com/x/.config?x=5e4e3a0e188a497e dashboard link: https://syzkaller.appspot.com/bug?extid=e4aa91d7f20c34417d4e compiler: Debian clang version 22.1.8 (++20260613092233+e80beda6e255-1~exp1~20260613092250.77), Debian LLD 22.1.8 syz repro: https://syzkaller.appspot.com/x/repro.syz?x=134d7d49580000 C reproducer: https://syzkaller.appspot.com/x/repro.c?x=1177ae25580000 Downloadable assets: disk image: https://storage.googleapis.com/syzbot-assets/18856a03a9a3/disk-1b78070a.raw.xz vmlinux: https://storage.googleapis.com/syzbot-assets/cc2bc68d7ef4/vmlinux-1b78070a.xz kernel image: https://storage.googleapis.com/syzbot-assets/05a5e00f8f91/bzImage-1b78070a.xz IMPORTANT: if you fix the issue, please add the following tag to the commit: Reported-by: syzbot+e4aa91d7f20c34417d4e@syzkaller.appspotmail.com rcu: INFO: rcu_preempt detected stalls on CPUs/tasks: rcu: 0-...!: (1 GPs behind) idle=a1cc/1/0x4000000000000000 softirq=17251/17256 fqs=2 rcu: Tasks blocked on level-0 rcu_node (CPUs 0-1): P4982/1:b..l rcu: (detected by 1, t=10502 jiffies, g=15057, q=530 ncpus=2) Sending NMI from CPU 1 to CPUs 0: NMI backtrace for cpu 0 CPU: 0 UID: 0 PID: 6026 Comm: cmp Not tainted syzkaller #0 PREEMPT(full) Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026 RIP: 0010:arch_atomic_try_cmpxchg arch/x86/include/asm/atomic.h:107 [inline] RIP: 0010:raw_atomic_try_cmpxchg_acquire include/linux/atomic/atomic-arch-fallback.h:2170 [inline] RIP: 0010:atomic_try_cmpxchg_acquire include/linux/atomic/atomic-instrumented.h:1302 [inline] RIP: 0010:queued_spin_lock include/asm-generic/qspinlock.h:112 [inline] RIP: 0010:do_raw_spin_lock+0x12b/0x2f0 kernel/locking/spinlock_debug.c:116 Code: 14 04 04 c7 44 24 40 00 00 00 00 48 89 df be 04 00 00 00 49 89 d6 e8 34 c1 93 00 48 8d 7c 24 40 be 04 00 00 00 e8 25 c1 93 00 <8b> 44 24 40 b9 01 00 00 00 f0 0f b1 0b 0f 85 20 01 00 00 43 c6 44 RSP: 0018:ffffc90000007c40 EFLAGS: 00000097 RAX: 00000000ffffff01 RBX: ffff88807cbce2a8 RCX: ffffffff81a3bd0b RDX: 0000000000000001 RSI: 0000000000000004 RDI: ffffc90000007c80 RBP: ffffc90000007ce8 R08: 0000000000000003 R09: 0000000000000004 R10: dffffc0000000000 R11: fffff52000000f90 R12: 1ffff92000000f8c R13: ffff88807cbce2b0 R14: dffffc0000000000 R15: 1ffff1100f979c56 FS: 0000000000000000(0000) GS:ffff888124ce0000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007f2972a84000 CR3: 0000000073aec000 CR4: 00000000003526f0 Call Trace: spin_lock include/linux/spinlock.h:347 [inline] advance_sched+0xc2/0xc80 net/sched/sch_taprio.c:931 __run_hrtimer kernel/time/hrtimer.c:2067 [inline] __hrtimer_run_queues+0x3bc/0xa10 kernel/time/hrtimer.c:2124 hrtimer_interrupt+0x4cd/0xaa0 kernel/time/hrtimer.c:2243 local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1051 [inline] __sysvec_apic_timer_interrupt+0x102/0x430 arch/x86/kernel/apic/apic.c:1068 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1062 [inline] sysvec_apic_timer_interrupt+0xa1/0xc0 arch/x86/kernel/apic/apic.c:1062 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:674 RIP: 0010:lock_acquire+0x232/0x350 kernel/locking/lockdep.c:5913 Code: ff ff ff e8 40 dc 3f 0a f7 44 24 10 00 02 00 00 0f 84 38 ff ff ff 65 48 8b 05 92 e7 f0 11 48 3b 44 24 50 75 33 fb 48 83 c4 58 <5b> 41 5c 41 5d 41 5e 41 5f 5d c3 cc cc cc cc cc 48 8d 3d 07 23 da RSP: 0018:ffffc900037eeda0 EFLAGS: 00000296 RAX: 27e016d3b0e95d00 RBX: 0000000000000000 RCX: 0000000000000046 RDX: 00000000e9c5941a RSI: ffffffff8e6fac39 RDI: ffffffff8c6d8b80 RBP: ffff88801df9be80 R08: 7a00000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: ffffffff8ed5c6e0 R12: ffffffff8ed5c6e0 R13: 0000000000000002 R14: 0000000000000000 R15: 0000000000000246 rcu_lock_acquire include/linux/rcupdate.h:309 [inline] rcu_read_lock include/linux/rcupdate.h:849 [inline] class_rcu_constructor include/linux/rcupdate.h:1216 [inline] unwind_next_frame+0xac/0x2550 arch/x86/kernel/unwind_orc.c:495 arch_stack_walk+0x11b/0x150 arch/x86/kernel/stacktrace.c:25 stack_trace_save+0xa9/0x100 kernel/stacktrace.c:122 kasan_save_stack mm/kasan/common.c:57 [inline] kasan_save_track+0x3e/0x80 mm/kasan/common.c:78 poison_kmalloc_redzone mm/kasan/common.c:398 [inline] __kasan_kmalloc+0x93/0xb0 mm/kasan/common.c:415 kasan_kmalloc include/linux/kasan.h:263 [inline] __kmalloc_cache_noprof+0x321/0x600 mm/slub.c:5563 _kmalloc_noprof include/linux/slab.h:991 [inline] slab_free_hook mm/slub.c:2700 [inline] slab_free mm/slub.c:6499 [inline] kmem_cache_free+0x156/0x650 mm/slub.c:6626 remove_vma mm/vma.c:517 [inline] vms_complete_munmap_vmas+0x897/0xbe0 mm/vma.c:1441 __mmap_complete+0xab/0x4b0 mm/vma.c:2721 __mmap_region mm/vma.c:2888 [inline] mmap_region+0x11d0/0x2240 mm/vma.c:2964 do_mmap+0xe0a/0x1300 mm/mmap.c:573 vm_mmap_pgoff+0x272/0x4e0 mm/util.c:581 ksys_mmap_pgoff+0x4dc/0x760 mm/mmap.c:619 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline] do_syscall_64+0x166/0x520 arch/x86/entry/syscall_64.c:84 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7f2972aaf242 Code: 08 00 04 00 00 eb e2 90 41 f7 c1 ff 0f 00 00 75 27 55 89 cd 53 48 89 fb 48 85 ff 74 33 41 89 ea 48 89 df b8 09 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 5e 5b 5d c3 0f 1f 00 c7 05 46 40 01 00 16 00 RSP: 002b:00007ffd9a1c6af8 EFLAGS: 00000206 ORIG_RAX: 0000000000000009 RAX: ffffffffffffffda RBX: 00007f29727db000 RCX: 00007f2972aaf242 RDX: 0000000000000001 RSI: 0000000000004000 RDI: 00007f29727db000 RBP: 0000000000000812 R08: 0000000000000003 R09: 000000000000b000 R10: 0000000000000812 R11: 0000000000000206 R12: 00007ffd9a1c6b80 R13: 00007f2972a83b20 R14: 00007ffd9a1c6f30 R15: 00000fffb3438d62 task:udevd state:R running task stack:26384 pid:4982 tgid:4982 ppid:1 task_flags:0x400140 flags:0x00080000 Call Trace: context_switch kernel/sched/core.c:5520 [inline] __schedule+0x17d4/0x5820 kernel/sched/core.c:7270 preempt_schedule_irq+0x4b/0x90 kernel/sched/core.c:7592 irqentry_exit_to_kernel_mode include/linux/irq-entry-common.h:539 [inline] irqentry_exit+0x14f/0x910 kernel/entry/common.c:167 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:674 RIP: 0010:kasan_check_byte include/linux/kasan.h:402 [inline] RIP: 0010:lock_acquire+0x6d/0x350 kernel/locking/lockdep.c:5882 Code: 9b 01 00 00 89 c0 48 0f a3 05 b7 eb d6 0e 73 0d e8 68 34 09 00 84 c0 0f 84 e2 01 00 00 83 3d a9 1c d7 0e 00 0f 84 e9 00 00 00 <48> 8b b4 24 88 00 00 00 4c 89 e7 e8 33 3a 94 00 83 3d 8c 1c d7 0e RSP: 0018:ffffc900044df268 EFLAGS: 00000202 RAX: 0000000000000001 RBX: 0000000000000000 RCX: 8000000000000001 RDX: 0000000000000000 RSI: ffffffff8c6d8b60 RDI: ffffffff8c6d8b20 RBP: 1ffff9200089be7c R08: 0000000000000000 R09: 0000000000000000 R10: ffffc900044df3f8 R11: ffffffff81b272d0 R12: ffffffff8ed5c6e0 R13: 0000000000000002 R14: 0000000000000000 R15: 0000000000000000 rcu_lock_acquire include/linux/rcupdate.h:309 [inline] rcu_read_lock include/linux/rcupdate.h:849 [inline] class_rcu_constructor include/linux/rcupdate.h:1216 [inline] unwind_next_frame+0xac/0x2550 arch/x86/kernel/unwind_orc.c:495 arch_stack_walk+0x11b/0x150 arch/x86/kernel/stacktrace.c:25 stack_trace_save+0xa9/0x100 kernel/stacktrace.c:122 kasan_save_stack mm/kasan/common.c:57 [inline] kasan_save_track+0x3e/0x80 mm/kasan/common.c:78 kasan_save_free_info+0x40/0x50 mm/kasan/generic.c:584 poison_slab_object mm/kasan/common.c:253 [inline] __kasan_slab_free+0x5c/0x80 mm/kasan/common.c:285 kasan_slab_free include/linux/kasan.h:235 [inline] slab_free_hook mm/slub.c:2748 [inline] slab_free mm/slub.c:6499 [inline] kfree+0x1c5/0x650 mm/slub.c:6792 tomoyo_check_open_permission+0x32c/0x470 security/tomoyo/file.c:791 security_file_open+0xa9/0x240 security/security.c:2739 do_dentry_open+0x4a0/0x1380 fs/open.c:973 vfs_open+0x3b/0x340 fs/open.c:1101 do_open fs/namei.c:4837 [inline] path_openat+0x1443/0x1d60 fs/namei.c:5000 do_file_open+0x23e/0x4a0 fs/namei.c:5029 do_sys_openat2+0x115/0x200 fs/open.c:1417 do_sys_open fs/open.c:1423 [inline] __do_sys_openat fs/open.c:1439 [inline] __se_sys_openat fs/open.c:1434 [inline] __x64_sys_openat+0x138/0x170 fs/open.c:1434 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline] do_syscall_64+0x166/0x520 arch/x86/entry/syscall_64.c:84 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7f22b3aa7407 RSP: 002b:00007fffdfe06440 EFLAGS: 00000202 ORIG_RAX: 0000000000000101 RAX: ffffffffffffffda RBX: 00007f22b425c880 RCX: 00007f22b3aa7407 RDX: 0000000000080141 RSI: 0000559823bb502e RDI: ffffffffffffff9c RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000 R10: 00000000000001a4 R11: 0000000000000202 R12: 00000000ffffffff R13: 00000000ffffffff R14: ffffffffffffffff R15: 0000000000000000 rcu: rcu_preempt kthread starved for 10498 jiffies! g15057 f0x0 RCU_GP_WAIT_FQS(5) ->state=R ->cpu=1 rcu: Unless rcu_preempt kthread gets sufficient CPU time, OOM is now expected behavior. rcu: RCU grace-period kthread stack dump: task:rcu_preempt state:R running task stack:27496 pid:17 tgid:17 ppid:2 task_flags:0x208040 flags:0x00080000 Call Trace: context_switch kernel/sched/core.c:5520 [inline] __schedule+0x17d4/0x5820 kernel/sched/core.c:7270 __schedule_loop kernel/sched/core.c:7347 [inline] schedule+0x164/0x2b0 kernel/sched/core.c:7362 schedule_timeout+0x152/0x2c0 kernel/time/sleep_timeout.c:99 rcu_gp_fqs_loop+0x30c/0x11f0 kernel/rcu/tree.c:2122 rcu_gp_kthread+0x9e/0x2b0 kernel/rcu/tree.c:2330 kthread+0x38b/0x480 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 rcu: Stack dump where RCU GP kthread last ran: CPU: 1 UID: 0 PID: 12 Comm: kworker/u8:0 Not tainted syzkaller #0 PREEMPT(full) Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026 Workqueue: events_unbound toggle_allocation_gate RIP: 0010:csd_lock_wait kernel/smp.c:363 [inline] RIP: 0010:csd_lock kernel/smp.c:396 [inline] RIP: 0010:smp_call_function_many_cond+0x61e/0x1500 kernel/smp.c:944 Code: b6 04 04 84 c0 0f 85 d5 03 00 00 44 8b 3b 44 89 fe 83 e6 01 31 ff e8 51 51 0c 00 41 83 e7 01 75 07 e8 46 4c 0c 00 eb 3f f3 90 <48> b8 00 00 00 00 00 fc ff df 41 0f b6 04 04 84 c0 75 0f f7 03 01 RSP: 0018:ffffc90000117720 EFLAGS: 00000293 RAX: ffffffff81bb677e RBX: ffff8880b8643708 RCX: ffff88801def8000 RDX: 0000000000000000 RSI: 0000000000000001 RDI: 0000000000000000 RBP: ffffc90000117870 R08: ffff88801def959f R09: 1ffff11003bdf2b3 R10: dffffc0000000000 R11: 0000000000000000 R12: 1ffff110170c86e1 R13: 0000000000000000 R14: ffff8880b8643700 R15: 0000000000000001 FS: 0000000000000000(0000) GS:ffff888124de0000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000555570500a38 CR3: 000000000eb48000 CR4: 00000000003526f0 Call Trace: on_each_cpu include/linux/smp.h:71 [inline] smp_text_poke_sync_each_cpu arch/x86/kernel/alternative.c:2602 [inline] smp_text_poke_batch_finish+0x5fd/0x1110 arch/x86/kernel/alternative.c:2812 arch_jump_label_transform_apply+0x1c/0x30 arch/x86/kernel/jump_label.c:146 static_key_enable_cpuslocked+0x128/0x240 kernel/jump_label.c:210 static_key_enable+0x1a/0x20 kernel/jump_label.c:223 toggle_allocation_gate+0xab/0x290 mm/kfence/core.c:902 process_one_work kernel/workqueue.c:3387 [inline] process_scheduled_works+0xc3d/0x1630 kernel/workqueue.c:3470 worker_thread+0xa47/0xfb0 kernel/workqueue.c:3551 kthread+0x38b/0x480 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 --- 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.