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Message-ID: <6942b4e1.050a0220.2a2f17.0000.GAE@google.com> Date: Wed, 17 Dec 2025 05:49:21 -0800 From: syzbot <syzbot+3e17d9c9a137bb913b61@...kaller.appspotmail.com> To: davem@...emloft.net, dsahern@...nel.org, edumazet@...gle.com, horms@...nel.org, kuba@...nel.org, linux-kernel@...r.kernel.org, linux-sctp@...r.kernel.org, lucien.xin@...il.com, marcelo.leitner@...il.com, netdev@...r.kernel.org, pabeni@...hat.com, syzkaller-bugs@...glegroups.com Subject: Re: [syzbot] [sctp?] INFO: rcu detected stall in inet6_rtm_newaddr (3) syzbot has found a reproducer for the following issue on: HEAD commit: 12b95d29eb97 Add linux-next specific files for 20251217 git tree: linux-next console output: https://syzkaller.appspot.com/x/log.txt?x=10c69d92580000 kernel config: https://syzkaller.appspot.com/x/.config?x=2b21d95ed921dffe dashboard link: https://syzkaller.appspot.com/bug?extid=3e17d9c9a137bb913b61 compiler: Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8 syz repro: https://syzkaller.appspot.com/x/repro.syz?x=10974a2a580000 C reproducer: https://syzkaller.appspot.com/x/repro.c?x=1003177c580000 Downloadable assets: disk image: https://storage.googleapis.com/syzbot-assets/9fb4b501730c/disk-12b95d29.raw.xz vmlinux: https://storage.googleapis.com/syzbot-assets/fc92d98fa8d2/vmlinux-12b95d29.xz kernel image: https://storage.googleapis.com/syzbot-assets/f25cfc55950a/bzImage-12b95d29.xz IMPORTANT: if you fix the issue, please add the following tag to the commit: Reported-by: syzbot+3e17d9c9a137bb913b61@...kaller.appspotmail.com rcu: INFO: rcu_preempt detected stalls on CPUs/tasks: rcu: Tasks blocked on level-0 rcu_node (CPUs 0-1): P6135/1:b..l P5964/2:b..l rcu: (detected by 1, t=10502 jiffies, g=14189, q=315 ncpus=2) task:syz-executor state:R running task stack:19496 pid:5964 tgid:5964 ppid:5963 task_flags:0x400140 flags:0x00080000 Call Trace: <TASK> context_switch kernel/sched/core.c:5258 [inline] __schedule+0x150e/0x5070 kernel/sched/core.c:6866 preempt_schedule_irq+0xb5/0x150 kernel/sched/core.c:7193 irqentry_exit+0x5d8/0x660 kernel/entry/common.c:216 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:697 RIP: 0010:orc_find arch/x86/kernel/unwind_orc.c:228 [inline] RIP: 0010:unwind_next_frame+0x214/0x23d0 arch/x86/kernel/unwind_orc.c:510 Code: ef 08 8b 15 6e 32 47 0c 8d 42 ff 44 39 f8 0f 86 78 04 00 00 44 89 f8 4c 8d 2c 85 f8 f5 e0 90 4c 89 e8 48 c1 e8 03 0f b6 04 28 <84> c0 48 89 eb 0f 85 2c 1c 00 00 45 8b 6d 00 44 89 f8 ff c0 48 8d RSP: 0018:ffffc900043eed38 EFLAGS: 00000a03 RAX: 0000000000000000 RBX: 0000000000000001 RCX: a87a6bbecf920600 RDX: 00000000000a60ce RSI: ffffffff8be075c0 RDI: ffffffff8be07580 RBP: dffffc0000000000 R08: ffffffff81742f85 R09: ffffffff8e13f8a0 R10: ffffc900043eee58 R11: ffffffff81ad9f20 R12: ffffffff8aa4f9ce R13: ffffffff910789dc R14: ffffc900043eee08 R15: 000000000009a4f9 arch_stack_walk+0x11c/0x150 arch/x86/kernel/stacktrace.c:25 stack_trace_save+0x9c/0xe0 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+0x3e2/0x700 mm/slub.c:5780 kmalloc_noprof include/linux/slab.h:957 [inline] kzalloc_noprof include/linux/slab.h:1094 [inline] sctp_inet6addr_event+0x37f/0x740 net/sctp/ipv6.c:86 notifier_call_chain+0x19d/0x3a0 kernel/notifier.c:85 atomic_notifier_call_chain+0xda/0x180 kernel/notifier.c:223 ipv6_add_addr+0xda9/0x1090 net/ipv6/addrconf.c:1186 inet6_addr_add+0x3c3/0xce0 net/ipv6/addrconf.c:3050 inet6_rtm_newaddr+0x93d/0xd20 net/ipv6/addrconf.c:5059 rtnetlink_rcv_msg+0x7cf/0xb70 net/core/rtnetlink.c:6958 netlink_rcv_skb+0x208/0x470 net/netlink/af_netlink.c:2550 netlink_unicast_kernel net/netlink/af_netlink.c:1318 [inline] netlink_unicast+0x82f/0x9e0 net/netlink/af_netlink.c:1344 netlink_sendmsg+0x805/0xb30 net/netlink/af_netlink.c:1894 sock_sendmsg_nosec+0x18f/0x1d0 net/socket.c:737 __sock_sendmsg net/socket.c:752 [inline] __sys_sendto+0x3ce/0x540 net/socket.c:2221 __do_sys_sendto net/socket.c:2228 [inline] __se_sys_sendto net/socket.c:2224 [inline] __x64_sys_sendto+0xde/0x100 net/socket.c:2224 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xfa/0xf80 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7f30ce1915dc RSP: 002b:00007ffc905dd720 EFLAGS: 00000293 ORIG_RAX: 000000000000002c RAX: ffffffffffffffda RBX: 00007f30cef14620 RCX: 00007f30ce1915dc RDX: 0000000000000040 RSI: 00007f30cef14670 RDI: 0000000000000003 RBP: 0000000000000000 R08: 00007ffc905dd774 R09: 000000000000000c R10: 0000000000000000 R11: 0000000000000293 R12: 0000000000000003 R13: 0000000000000000 R14: 00007f30cef14670 R15: 0000000000000000 </TASK> task:sed state:R running task stack:24312 pid:6135 tgid:6135 ppid:6134 task_flags:0x400000 flags:0x00080000 Call Trace: <TASK> context_switch kernel/sched/core.c:5258 [inline] __schedule+0x150e/0x5070 kernel/sched/core.c:6866 preempt_schedule_irq+0xb5/0x150 kernel/sched/core.c:7193 irqentry_exit+0x5d8/0x660 kernel/entry/common.c:216 asm_sysvec_reschedule_ipi+0x1a/0x20 arch/x86/include/asm/idtentry.h:702 RIP: 0010:arch_atomic64_read arch/x86/include/asm/atomic64_64.h:-1 [inline] RIP: 0010:raw_atomic64_read include/linux/atomic/atomic-arch-fallback.h:2583 [inline] RIP: 0010:atomic64_read include/linux/atomic/atomic-instrumented.h:1611 [inline] RIP: 0010:ktime_get_coarse_real_ts64_mg+0x37/0x1e0 kernel/time/timekeeping.c:2445 Code: 53 48 83 ec 10 48 89 fb e8 36 04 12 00 48 c7 c7 c0 12 e1 8d be 08 00 00 00 e8 65 62 78 00 48 8b 05 5e 4d 31 0c 48 89 44 24 08 <4c> 8d 73 08 49 89 dd 49 c1 ed 03 4c 89 f0 48 c1 e8 03 48 89 04 24 RSP: 0018:ffffc900034d75b8 EFLAGS: 00000256 RAX: 000000261054af24 RBX: ffffc900034d7640 RCX: ffffffff81afc55b RDX: 0000000000000000 RSI: 0000000000000008 RDI: ffffffff8de112c0 RBP: ffffc900034d76b8 R08: ffffffff8de112c7 R09: 1ffffffff1bc2258 R10: dffffc0000000000 R11: fffffbfff1bc2259 R12: dffffc0000000000 R13: dffffc0000000000 R14: ffffc900034d7640 R15: dffffc0000000000 current_time+0x8e/0x360 fs/inode.c:2343 atime_needs_update+0x320/0x6d0 fs/inode.c:2206 pick_link+0x549/0xfa0 fs/namei.c:1983 step_into_slowpath+0x53b/0x7d0 fs/namei.c:2066 step_into fs/namei.c:2091 [inline] walk_component fs/namei.c:2227 [inline] link_path_walk+0xd50/0x18d0 fs/namei.c:2589 path_openat+0x2b0/0x3840 fs/namei.c:4782 do_filp_open+0x1fa/0x410 fs/namei.c:4813 do_sys_openat2+0x121/0x200 fs/open.c:1391 do_sys_open fs/open.c:1397 [inline] __do_sys_openat fs/open.c:1413 [inline] __se_sys_openat fs/open.c:1408 [inline] __x64_sys_openat+0x138/0x170 fs/open.c:1408 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xfa/0xf80 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7fabfcd360ba RSP: 002b:00007fff94803a88 EFLAGS: 00000206 ORIG_RAX: 0000000000000101 RAX: ffffffffffffffda RBX: 00007fff94803b00 RCX: 00007fabfcd360ba RDX: 0000000000080000 RSI: 00007fff94803b00 RDI: 00000000ffffff9c RBP: 00007fff94803af0 R08: 00007fff94803cf7 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000206 R12: 0000000000000017 R13: 00007fabfcd0a000 R14: 00007fff94803d10 R15: 0000000000000000 </TASK> rcu: rcu_preempt kthread starved for 10598 jiffies! g14189 f0x0 RCU_GP_WAIT_FQS(5) ->state=0x0 ->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:27168 pid:16 tgid:16 ppid:2 task_flags:0x208040 flags:0x00080000 Call Trace: <TASK> context_switch kernel/sched/core.c:5258 [inline] __schedule+0x150e/0x5070 kernel/sched/core.c:6866 __schedule_loop kernel/sched/core.c:6948 [inline] schedule+0x165/0x360 kernel/sched/core.c:6963 schedule_timeout+0x12b/0x270 kernel/time/sleep_timeout.c:99 rcu_gp_fqs_loop+0x301/0x1540 kernel/rcu/tree.c:2083 rcu_gp_kthread+0x99/0x390 kernel/rcu/tree.c:2285 kthread+0x711/0x8a0 kernel/kthread.c:463 ret_from_fork+0x599/0xb30 arch/x86/kernel/process.c:158 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:246 </TASK> rcu: Stack dump where RCU GP kthread last ran: CPU: 1 UID: 0 PID: 0 Comm: swapper/1 Not tainted syzkaller #0 PREEMPT(full) Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025 RIP: 0010:pv_native_safe_halt+0x13/0x20 arch/x86/kernel/paravirt.c:82 Code: cc cc cc cc 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 4e 2b 00 f3 0f 1e fa fb f4 <e9> 48 ee 02 00 cc cc cc cc cc cc cc cc 90 90 90 90 90 90 90 90 90 RSP: 0018:ffffc90000197de0 EFLAGS: 000002c6 RAX: fcd00228fb9d7700 RBX: ffffffff8197888a RCX: fcd00228fb9d7700 RDX: 0000000000000001 RSI: ffffffff8d99597b RDI: ffffffff8be075e0 RBP: ffffc90000197f10 R08: ffff8880b87336db R09: 1ffff110170e66db R10: dffffc0000000000 R11: ffffed10170e66dc R12: ffffffff8fa20e70 R13: 1ffff11003adcb70 R14: 0000000000000001 R15: 0000000000000001 FS: 0000000000000000(0000) GS:ffff888125d2d000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007fabfca09a10 CR3: 0000000076504000 CR4: 00000000003526f0 Call Trace: <TASK> arch_safe_halt arch/x86/include/asm/paravirt.h:107 [inline] default_idle+0x13/0x20 arch/x86/kernel/process.c:767 default_idle_call+0x73/0xb0 kernel/sched/idle.c:122 cpuidle_idle_call kernel/sched/idle.c:191 [inline] do_idle+0x1ea/0x520 kernel/sched/idle.c:332 cpu_startup_entry+0x44/0x60 kernel/sched/idle.c:430 start_secondary+0x101/0x110 arch/x86/kernel/smpboot.c:312 common_startup_64+0x13e/0x147 </TASK> --- 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.
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