Re: [syzbot] [mm?] INFO: rcu detected stall in sys_munmap (2)

[syzbot <syzbot+8785aaf121cfb2141e0d@syzkaller.appspotmail.com>]

Hello,

syzbot has tested the proposed patch but the reproducer is still triggering an issue:
INFO: rcu detected stall in corrupted

rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 	Tasks blocked on level-0 rcu_node (CPUs 0-1): P5218/1:b..l
rcu: 	(detected by 0, t=10502 jiffies, g=10417, q=327 ncpus=2)
task:udevd           state:R  running task     stack:26640 pid:5218  tgid:5218  ppid:1      task_flags:0x400140 flags:0x00004002
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5357 [inline]
 __schedule+0x1190/0x5de0 kernel/sched/core.c:6961
 preempt_schedule_irq+0x51/0x90 kernel/sched/core.c:7288
 irqentry_exit+0x36/0x90 kernel/entry/common.c:197
 asm_sysvec_reschedule_ipi+0x1a/0x20 arch/x86/include/asm/idtentry.h:707
RIP: 0010:lock_acquire+0x30/0x350 kernel/locking/lockdep.c:5828
Code: 4d 89 cf 41 56 41 89 f6 41 55 41 89 d5 41 54 45 89 c4 55 89 cd 53 48 89 fb 48 83 ec 38 65 48 8b 05 0d 79 3e 12 48 89 44 24 30 <31> c0 66 90 65 8b 05 29 79 3e 12 83 f8 07 0f 87 bc 02 00 00 89 c0
RSP: 0018:ffffc90003d0f530 EFLAGS: 00000286
RAX: 4b548df46ee33600 RBX: ffffffff8e5c11e0 RCX: 0000000000000002
RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffffffff8e5c11e0
RBP: 0000000000000002 R08: 0000000000000000 R09: 0000000000000000
R10: ffffc90003d0f618 R11: 00000000000135a3 R12: 0000000000000000
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
 rcu_lock_acquire include/linux/rcupdate.h:331 [inline]
 rcu_read_lock include/linux/rcupdate.h:841 [inline]
 class_rcu_constructor include/linux/rcupdate.h:1155 [inline]
 unwind_next_frame+0xd1/0x20a0 arch/x86/kernel/unwind_orc.c:479
 arch_stack_walk+0x94/0x100 arch/x86/kernel/stacktrace.c:25
 stack_trace_save+0x8e/0xc0 kernel/stacktrace.c:122
 kasan_save_stack+0x33/0x60 mm/kasan/common.c:47
 kasan_save_track+0x14/0x30 mm/kasan/common.c:68
 kasan_save_free_info+0x3b/0x60 mm/kasan/generic.c:576
 poison_slab_object mm/kasan/common.c:243 [inline]
 __kasan_slab_free+0x60/0x70 mm/kasan/common.c:275
 kasan_slab_free include/linux/kasan.h:233 [inline]
 slab_free_hook mm/slub.c:2417 [inline]
 slab_free mm/slub.c:4680 [inline]
 kfree+0x2b4/0x4d0 mm/slub.c:4879
 tomoyo_realpath_from_path+0x19f/0x6e0 security/tomoyo/realpath.c:286
 tomoyo_get_realpath security/tomoyo/file.c:151 [inline]
 tomoyo_path_perm+0x274/0x460 security/tomoyo/file.c:822
 security_inode_getattr+0x116/0x290 security/security.c:2377
 vfs_getattr fs/stat.c:259 [inline]
 vfs_statx_path fs/stat.c:299 [inline]
 vfs_statx+0x121/0x3f0 fs/stat.c:356
 vfs_fstatat+0x7b/0xf0 fs/stat.c:375
 __do_sys_newfstatat+0x97/0x120 fs/stat.c:542
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xcd/0x4c0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f47f6d11b0a
RSP: 002b:00007ffd84c35818 EFLAGS: 00000246 ORIG_RAX: 0000000000000106
RAX: ffffffffffffffda RBX: 0000559b20c5e418 RCX: 00007f47f6d11b0a
RDX: 00007ffd84c35820 RSI: 0000559b20c4cef3 RDI: 00000000ffffff9c
RBP: 0000559b5aa6d668 R08: 00063d641a57c867 R09: 00007f47f7457000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000001
R13: 00007ffd84c35820 R14: 0000000000000000 R15: 00063d641a57c867
 </TASK>
rcu: rcu_preempt kthread starved for 966 jiffies! g10417 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:28936 pid:16    tgid:16    ppid:2      task_flags:0x208040 flags:0x00004000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5357 [inline]
 __schedule+0x1190/0x5de0 kernel/sched/core.c:6961
 __schedule_loop kernel/sched/core.c:7043 [inline]
 schedule+0xe7/0x3a0 kernel/sched/core.c:7058
 schedule_timeout+0x123/0x290 kernel/time/sleep_timeout.c:99
 rcu_gp_fqs_loop+0x1ea/0xb00 kernel/rcu/tree.c:2083
 rcu_gp_kthread+0x270/0x380 kernel/rcu/tree.c:2285
 kthread+0x3c2/0x780 kernel/kthread.c:463
 ret_from_fork+0x5d7/0x6f0 arch/x86/kernel/process.c:148
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>
rcu: Stack dump where RCU GP kthread last ran:
Sending NMI from CPU 0 to CPUs 1:
NMI backtrace for cpu 1
CPU: 1 UID: 0 PID: 6556 Comm: syz.1.23 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/12/2025
RIP: 0010:arch_static_branch arch/x86/include/asm/jump_label.h:36 [inline]
RIP: 0010:native_write_msr arch/x86/include/asm/msr.h:139 [inline]
RIP: 0010:wrmsrq arch/x86/include/asm/msr.h:199 [inline]
RIP: 0010:native_apic_msr_write arch/x86/include/asm/apic.h:212 [inline]
RIP: 0010:native_apic_msr_write+0x28/0x40 arch/x86/include/asm/apic.h:206
Code: 90 90 f3 0f 1e fa 8d 87 30 ff ff ff 83 e0 ef 74 20 89 f8 83 e0 ef 83 f8 20 74 16 c1 ef 04 31 d2 89 f0 8d 8f 00 08 00 00 0f 30 <66> 90 c3 cc cc cc cc c3 cc cc cc cc 89 f6 31 d2 89 cf e9 b1 4d ae
RSP: 0018:ffffc900031479f0 EFLAGS: 00000046
RAX: 000000000000003e RBX: ffff8880b8523a00 RCX: 0000000000000838
RDX: 0000000000000000 RSI: 000000000000003e RDI: 0000000000000038
RBP: 000000000000003e R08: 0000000000000005 R09: 000000000000003f
R10: 0000000000000020 R11: ffffffff9b0d2580 R12: dffffc0000000000
R13: 0000000000000000 R14: 0000000000000020 R15: ffffed10170a4745
FS:  0000555558775500(0000) GS:ffff8881247bc000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000000c00732e000 CR3: 0000000077210000 CR4: 00000000003526f0
Call Trace:
 <TASK>
 apic_write arch/x86/include/asm/apic.h:405 [inline]
 lapic_next_event+0x10/0x20 arch/x86/kernel/apic/apic.c:416
 clockevents_program_min_delta+0x173/0x3a0 kernel/time/clockevents.c:248
 clockevents_program_event+0x2a6/0x380 kernel/time/clockevents.c:336
 tick_program_event+0xa9/0x140 kernel/time/tick-oneshot.c:44
 __hrtimer_reprogram kernel/time/hrtimer.c:685 [inline]
 __hrtimer_reprogram kernel/time/hrtimer.c:659 [inline]
 hrtimer_reprogram+0x27b/0x450 kernel/time/hrtimer.c:868
 hrtimer_start_range_ns+0x9d4/0xfc0 kernel/time/hrtimer.c:1330
 __posixtimer_deliver_signal kernel/time/posix-timers.c:322 [inline]
 posixtimer_deliver_signal+0x30d/0x6b0 kernel/time/posix-timers.c:348
 dequeue_signal+0x307/0x520 kernel/signal.c:660
 get_signal+0x602/0x26d0 kernel/signal.c:2914
 arch_do_signal_or_restart+0x8f/0x7d0 arch/x86/kernel/signal.c:337
 exit_to_user_mode_loop+0x84/0x110 kernel/entry/common.c:40
 exit_to_user_mode_prepare include/linux/irq-entry-common.h:225 [inline]
 syscall_exit_to_user_mode_work include/linux/entry-common.h:175 [inline]
 syscall_exit_to_user_mode include/linux/entry-common.h:210 [inline]
 do_syscall_64+0x3f6/0x4c0 arch/x86/entry/syscall_64.c:100
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f5114d8ebe9
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffcc5e18098 EFLAGS: 00000246
RAX: fffffffffffffffc RBX: 00000000000231ee RCX: 00007f5114d8ebe9
RDX: 0000000000000000 RSI: 0000000000000080 RDI: 00007f5114fb5fac
RBP: 0000000000000032 R08: 00007f5115bce000 R09: 00000012c5e1838f
R10: 00007ffcc5e18190 R11: 0000000000000246 R12: 00007f5114fb5fac
R13: 00007ffcc5e18190 R14: 0000000000023220 R15: 00007ffcc5e181b0
 </TASK>


Tested on:

commit:         a1617343 skip the validate_mm() for stall test
git tree:       git://git.infradead.org/users/jedix/linux-maple.git no_validate
console output: https://syzkaller.appspot.com/x/log.txt?x=13441fbc580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=d4703ac89d9e185a
dashboard link: https://syzkaller.appspot.com/bug?extid=8785aaf121cfb2141e0d
compiler:       gcc (Debian 12.2.0-14+deb12u1) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40

Note: no patches were applied.