[v6.6] INFO: rcu detected stall in sys_madvise

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 0bbbd97a442d Linux 6.6.112
git tree: linux-6.6.y
console output: https://syzkaller.appspot.com/x/log.txt?x=13698b04580000
kernel config: https://syzkaller.appspot.com/x/.config?x=12606d4b8832c7e4
dashboard link: https://syzkaller.appspot.com/bug?extid=f63f463d592cf4a93358
compiler: Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8

Unfortunately, I don't have any reproducer for this issue yet.

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/7e387d57d751/disk-0bbbd97a.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/810d42505365/vmlinux-0bbbd97a.xz
kernel image: https://storage.googleapis.com/syzbot-assets/5d2fe115c227/bzImage-0bbbd97a.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+f63f46...@syzkaller.appspotmail.com

rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: (detected by 1, t=10502 jiffies, g=70937, q=258 ncpus=2)
rcu: All QSes seen, last rcu_preempt kthread activity 10502 (4295050962-4295040460), jiffies_till_next_fqs=1, root ->qsmask 0x0
rcu: rcu_preempt kthread starved for 10502 jiffies! g70937 f0x2 RCU_GP_WAIT_FQS(5) ->state=0x0 ->cpu=0
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:27688 pid:17 ppid:2 flags:0x00004000
Call Trace:
<TASK>
context_switch kernel/sched/core.c:5380 [inline]
__schedule+0x14d2/0x44d0 kernel/sched/core.c:6699
schedule+0xbd/0x170 kernel/sched/core.c:6773
schedule_timeout+0x160/0x280 kernel/time/timer.c:2167
rcu_gp_fqs_loop+0x302/0x1560 kernel/rcu/tree.c:1667
rcu_gp_kthread+0x99/0x380 kernel/rcu/tree.c:1866
kthread+0x2fa/0x390 kernel/kthread.c:388
ret_from_fork+0x48/0x80 arch/x86/kernel/process.c:152
ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:293
</TASK>
rcu: Stack dump where RCU GP kthread last ran:
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 PID: 15410 Comm: syz.1.2397 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/18/2025
RIP: 0010:__lock_acquire+0x6a90/0x7c80 kernel/locking/lockdep.c:5107
Code: 00 00 00 00 fc ff df e9 e5 9b ff ff 44 89 f9 80 e1 07 80 c1 03 38 c1 0f 8c a8 a2 ff ff 4c 89 ff e8 05 80 75 00 e9 9b a2 ff ff <48> c7 c1 80 e4 ea 96 80 e1 07 80 c1 03 38 c1 0f 8c ce a2 ff ff 48
RSP: 0018:ffffc90000007900 EFLAGS: 00000002
RAX: 0000000000000004 RBX: 0000000000084002 RCX: ffffffff8167b074
RDX: 0000000000000000 RSI: 0000000000000008 RDI: ffffffff90da7508
RBP: ffffc90000007b48 R08: dffffc0000000000 R09: 1ffffffff21b4ea1
R10: dffffc0000000000 R11: fffffbfff21b4ea2 R12: 0000000000000000
R13: ffff888021199e00 R14: ffff88802119a958 R15: ffff88802119a978
FS: 00007fb7837b46c0(0000) GS:ffff8880b8e00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000000110c33ac31 CR3: 000000002ff2c000 CR4: 00000000003506f0
DR0: ffffffffffffffff DR1: 00000000000001f8 DR2: 0000000000000083
DR3: ffffffffefffff15 DR6: 00000000ffff0ff0 DR7: 0000000000000400
Call Trace:
<IRQ>
lock_acquire+0x197/0x410 kernel/locking/lockdep.c:5754
__raw_spin_lock_irq include/linux/spinlock_api_smp.h:119 [inline]
_raw_spin_lock_irq+0xa3/0xe0 kernel/locking/spinlock.c:170
__run_hrtimer kernel/time/hrtimer.c:1754 [inline]
__hrtimer_run_queues+0x5e3/0xc40 kernel/time/hrtimer.c:1814
hrtimer_interrupt+0x3c9/0x9c0 kernel/time/hrtimer.c:1876
local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1077 [inline]
__sysvec_apic_timer_interrupt+0xfb/0x3b0 arch/x86/kernel/apic/apic.c:1094
instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1088 [inline]
sysvec_apic_timer_interrupt+0x9f/0xc0 arch/x86/kernel/apic/apic.c:1088
</IRQ>
<TASK>
asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:687
RIP: 0010:lock_release+0x57c/0x8b0 kernel/locking/lockdep.c:5778
Code: 00 00 00 00 9c 8f 84 24 80 00 00 00 f6 84 24 81 00 00 00 02 75 75 f7 44 24 50 00 02 00 00 74 01 fb 48 c7 44 24 60 0e 36 e0 45 <4b> c7 04 2f 00 00 00 00 66 43 c7 44 2f 09 00 00 43 c6 44 2f 0b 00
RSP: 0018:ffffc900050bf360 EFLAGS: 00000206
RAX: 0000000000000001 RBX: 9423cc4e7db96bb3 RCX: d4060c9848d87400
RDX: 0000000000000003 RSI: ffffffff8aaace60 RDI: ffffffff8afc64c0
RBP: ffffc900050bf470 R08: ffffffff8e4a856f R09: 1ffffffff1c950ad
R10: dffffc0000000000 R11: fffffbfff1c950ae R12: ffff88802119a958
R13: dffffc0000000000 R14: ffff88802119a8d0 R15: 1ffff92000a17e78
ptep_get_and_clear_full+0xbc/0xc0 arch/x86/include/asm/pgtable.h:-1
madvise_cold_or_pageout_pte_range+0xb63/0x2050 mm/madvise.c:500
walk_pmd_range mm/pagewalk.c:143 [inline]
walk_pud_range mm/pagewalk.c:221 [inline]
walk_p4d_range mm/pagewalk.c:256 [inline]
walk_pgd_range+0xc4c/0x1820 mm/pagewalk.c:293
__walk_page_range+0x134/0x5b0 mm/pagewalk.c:395
walk_page_range+0x345/0x510 mm/pagewalk.c:521
madvise_pageout_page_range mm/madvise.c:592 [inline]
madvise_pageout mm/madvise.c:619 [inline]
madvise_vma_behavior mm/madvise.c:1037 [inline]
madvise_walk_vmas mm/madvise.c:1266 [inline]
do_madvise+0x23cf/0x3710 mm/madvise.c:1446
__do_sys_madvise mm/madvise.c:1459 [inline]
__se_sys_madvise mm/madvise.c:1457 [inline]
__x64_sys_madvise+0xa6/0xc0 mm/madvise.c:1457
do_syscall_x64 arch/x86/entry/common.c:51 [inline]
do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:81
entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7fb78558eec9
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:00007fb7837b4038 EFLAGS: 00000246 ORIG_RAX: 000000000000001c
RAX: ffffffffffffffda RBX: 00007fb7857e6180 RCX: 00007fb78558eec9
RDX: 0000000000000015 RSI: 0000000000600003 RDI: 0000200000000000
RBP: 00007fb785611f91 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fb7857e6218 R14: 00007fb7857e6180 R15: 00007ffc6aac18a8
</TASK>


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