[syzbot] [kernel?] INFO: rcu detected stall in kthread (6)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: af5e34a41cd6 Merge tag 'mtd/fixes-for-7.2-rc4' of git://gi..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=13edbcb9580000
kernel config: https://syzkaller.appspot.com/x/.config?x=d69870d5e052935f
dashboard link: https://syzkaller.appspot.com/bug?extid=2d47e0896b84fae323c7
compiler: gcc (Debian 14.2.0-19) 14.2.0, GNU ld (GNU Binutils for Debian) 2.44
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=10388746580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/b3903f297dbd/disk-af5e34a4.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/e6f4d983bd3e/vmlinux-af5e34a4.xz
kernel image: https://storage.googleapis.com/syzbot-assets/0e019af92bd8/bzImage-af5e34a4.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+2d47e0...@syzkaller.appspotmail.com

rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: (detected by 1, t=10502 jiffies, g=13273, q=641 ncpus=2)
rcu: All QSes seen, last rcu_preempt kthread activity 10502 (4294959287-4294948785), jiffies_till_next_fqs=1, root ->qsmask 0x0
rcu: rcu_preempt kthread starved for 10502 jiffies! g13273 f0x0 RCU_GP_INIT(4) ->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:27672 pid:16 tgid:16 ppid:2 task_flags:0x208040 flags:0x00080000
Call Trace:
<TASK>
context_switch kernel/sched/core.c:5510 [inline]
__schedule+0x125c/0x6730 kernel/sched/core.c:7234
preempt_schedule_irq+0x50/0x90 kernel/sched/core.c:7556
irqentry_exit_to_kernel_mode_preempt include/linux/irq-entry-common.h:468 [inline]
irqentry_exit_to_kernel_mode include/linux/irq-entry-common.h:539 [inline]
irqentry_exit+0x205/0xa00 kernel/entry/common.c:167
asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:674
RIP: 0010:rcu_gp_init+0xbb4/0x1480 kernel/rcu/tree.c:1983
Code: d0 0c 48 83 fd 02 0f 83 32 05 00 00 48 8d 44 ad 00 48 c1 e0 08 48 05 c0 14 bf 8e 48 39 c3 0f 83 29 01 00 00 8b 3d 2c 61 84 19 <e8> 37 82 ff ff 48 89 df e8 6f aa cd 09 48 89 c5 e8 97 d1 ca 09 41
RSP: 0018:ffffc90000157cb8 EFLAGS: 00000282
RAX: ffffed1003d5809e RBX: ffffffff8ebf14c0 RCX: 0000000000000000
RDX: 0000000000000000 RSI: ffff88801eac04f0 RDI: 0000000000000000
RBP: dffffc0000000000 R08: 0000000000000001 R09: 0000000000000000
R10: 0000000000000004 R11: 0000000000000000 R12: ffff88801eac0000
R13: ffffffff94654540 R14: dffffc0000000000 R15: ffffffff8ebf19c0
rcu_gp_kthread+0xb2/0x230 kernel/rcu/tree.c:2315
kthread+0x370/0x450 kernel/kthread.c:436
ret_from_fork+0x72b/0xd50 arch/x86/kernel/process.c:158
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 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 UID: 0 PID: 6021 Comm: syz.0.43 Not tainted syzkaller #0 PREEMPT(full)
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 06/10/2026
RIP: 0010:bytes_is_nonzero mm/kasan/generic.c:98 [inline]
RIP: 0010:memory_is_nonzero mm/kasan/generic.c:115 [inline]
RIP: 0010:memory_is_poisoned_n mm/kasan/generic.c:140 [inline]
RIP: 0010:memory_is_poisoned mm/kasan/generic.c:172 [inline]
RIP: 0010:check_region_inline mm/kasan/generic.c:191 [inline]
RIP: 0010:kasan_check_range+0x180/0x1e0 mm/kasan/generic.c:200
Code: ff ff ff 48 85 d2 74 98 48 01 ea eb 1a 66 66 2e 0f 1f 84 00 00 00 00 00 66 90 48 83 c0 01 48 39 d0 0f 84 79 ff ff ff 80 38 00 <74> ee e9 57 ff ff ff b8 01 00 00 00 c3 cc cc cc cc 48 29 c3 48 89
RSP: 0018:ffffc90000007fb8 EFLAGS: 00000046
RAX: fffffbfff22447f2 RBX: fffffbfff22447f3 RCX: ffffffff81b53036
RDX: fffffbfff22447f3 RSI: 0000000000000008 RDI: ffffffff91223f90
RBP: fffffbfff22447f2 R08: 0000000000000000 R09: fffffbfff22447f2
R10: ffffffff91223f97 R11: ffffc90000007ff8 R12: 0000000000000000
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
FS: 00007fc1339f96c0(0000) GS:ffff888123de8000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000200000000058 CR3: 0000000076794000 CR4: 00000000003526f0
Call Trace:
<IRQ>
instrument_atomic_read include/linux/instrumented.h:82 [inline]
_test_bit include/asm-generic/bitops/instrumented-non-atomic.h:141 [inline]
cpumask_test_cpu include/linux/cpumask.h:651 [inline]
cpu_online include/linux/cpumask.h:1233 [inline]
trace_local_timer_entry arch/x86/include/asm/trace/irq_vectors.h:40 [inline]
__sysvec_apic_timer_interrupt+0x66/0x470 arch/x86/kernel/apic/apic.c:1067
instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1062 [inline]
sysvec_apic_timer_interrupt+0x9e/0xc0 arch/x86/kernel/apic/apic.c:1062
</IRQ>
<TASK>
asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:674
RIP: 0010:lock_acquire+0x5e/0x370 kernel/locking/lockdep.c:5872
Code: 05 fb 0d 7e 12 83 f8 07 0f 87 da 00 00 00 48 0f a3 05 46 cd 3c 0f 0f 82 ac 02 00 00 8b 35 0e 01 3d 0f 85 f6 0f 85 c7 00 00 00 <48> 8b 44 24 30 65 48 2b 05 9d 0d 7e 12 0f 85 ec 02 00 00 48 83 c4
RSP: 0018:ffffc90003a1fa38 EFLAGS: 00000206
RAX: 0000000000000046 RBX: 0000000000000000 RCX: edbc7214ceca522d
RDX: 0000000000000000 RSI: ffffffff8e17e526 RDI: ffffffff8c401280
RBP: ffff88807ca069b8 R08: 00000000ffffffff R09: 00000000000001c8
R10: 0000000000000200 R11: 0000000000000000 R12: 0000000000000001
R13: 0000000000000001 R14: 0000000000000000 R15: 0000000000000000
__might_fault+0xde/0x140 mm/memory.c:7292
__copy_from_user include/linux/uaccess.h:115 [inline]
check_xstate_in_sigframe arch/x86/kernel/fpu/signal.c:35 [inline]
__fpu_restore_sig+0xee/0x13b0 arch/x86/kernel/fpu/signal.c:340
fpu__restore_sig+0x151/0x190 arch/x86/kernel/fpu/signal.c:485
restore_sigcontext+0x4cb/0x6a0 arch/x86/kernel/signal_64.c:95
__do_sys_rt_sigreturn+0x229/0x2c0 arch/x86/kernel/signal_64.c:268
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0x115/0x870 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fc132b9de97
Code: 83 c8 ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 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 e8 ff ff ff f7 d8 64 89
RSP: 002b:00007fc1339f90e8 EFLAGS: 00000246
RAX: 00000000000000ca RBX: 00007fc132e25fa8 RCX: 00007fc132b9de99
RDX: 0000000000000000 RSI: 0000000000000080 RDI: 00007fc132e25fa8
RBP: 00007fc132e25fa0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fc132e26038 R14: 00007ffc24e24500 R15: 00007ffc24e245e8
</TASK>


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