[v6.6] INFO: rcu detected stall in sys_mkdir (2)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 4791134e4aeb Linux 6.6.118
git tree: linux-6.6.y
console output: https://syzkaller.appspot.com/x/log.txt?x=179fdcc2580000
kernel config: https://syzkaller.appspot.com/x/.config?x=12606d4b8832c7e4
dashboard link: https://syzkaller.appspot.com/bug?extid=75500577f5198015d005
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/ca168ecfe887/disk-4791134e.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/adda86b1a76b/vmlinux-4791134e.xz
kernel image: https://storage.googleapis.com/syzbot-assets/cc2019969cb7/bzImage-4791134e.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+755005...@syzkaller.appspotmail.com

rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: Tasks blocked on level-0 rcu_node (CPUs 0-1): P8401/1:b..l
rcu: (detected by 1, t=10502 jiffies, g=34093, q=344 ncpus=2)
task:syz.9.552 state:R running task stack:25584 pid:8401 ppid:7690 flags:0x00004000
Call Trace:
<TASK>
context_switch kernel/sched/core.c:5380 [inline]
__schedule+0x14d2/0x44d0 kernel/sched/core.c:6699
preempt_schedule_irq+0xb5/0x140 kernel/sched/core.c:7009
irqentry_exit+0x67/0x70 kernel/entry/common.c:438
asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:687
RIP: 0010:security_inode_permission+0x48/0xf0 security/security.c:2109
Code: 7e ae ac fd 4d 8d 7e 1c 4c 89 f8 48 c1 e8 03 42 0f b6 04 28 84 c0 0f 85 93 00 00 00 45 8b 3f 44 89 fe 81 e6 00 02 00 00 31 ed <31> ff e8 01 b2 ac fd 41 81 e7 00 02 00 00 75 6e 49 c7 c7 00 5b 7d
RSP: 0018:ffffc9000f96f9e8 EFLAGS: 00000246
RAX: 0000000000000000 RBX: 0000000000000081 RCX: 0000000000080000
RDX: ffffc90011ca7000 RSI: 0000000000000000 RDI: 0000000000000256
RBP: 0000000000000000 R08: ffff888025548000 R09: 0000000000000002
R10: 000000000000002f R11: 0000000000000002 R12: ffffc9000f96fbf0
R13: dffffc0000000000 R14: ffff8880559722b0 R15: 0000000000000000
may_lookup fs/namei.c:1728 [inline]
link_path_walk+0x286/0xe00 fs/namei.c:2279
path_parentat fs/namei.c:2538 [inline]
__filename_parentat+0x205/0x610 fs/namei.c:2562
filename_parentat fs/namei.c:2580 [inline]
filename_create+0xd0/0x460 fs/namei.c:3871
do_mkdirat+0xa1/0x440 fs/namei.c:4136
__do_sys_mkdir fs/namei.c:4164 [inline]
__se_sys_mkdir fs/namei.c:4162 [inline]
__x64_sys_mkdir+0x6e/0x80 fs/namei.c:4162
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: 0033:0x7f834b38f749
RSP: 002b:00007f834c1e4038 EFLAGS: 00000246 ORIG_RAX: 0000000000000053
RAX: ffffffffffffffda RBX: 00007f834b5e5fa0 RCX: 00007f834b38f749
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 00002000000004c0
RBP: 00007f834b413f91 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f834b5e6038 R14: 00007f834b5e5fa0 R15: 00007fff100a7958
</TASK>
rcu: rcu_preempt kthread starved for 10532 jiffies! g34093 f0x0 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:27032 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:2168
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: 0 Comm: swapper/0 Not tainted syzkaller #0
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:148
Code: cc cc cc cc cc cc cc f3 0f 1e fa 0f 0b 66 2e 0f 1f 84 00 00 00 00 00 f3 0f 1e fa 66 90 0f 00 2d a3 14 39 00 f3 0f 1e fa fb f4 <c3> cc cc cc cc cc cc cc cc cc cc cc cc 66 0f 1f 00 55 41 57 41 56
RSP: 0018:ffffffff8ca07d80 EFLAGS: 000002c6
RAX: 8a149fa1c8941400 RBX: ffffffff8161881b RCX: 8a149fa1c8941400
RDX: 0000000000000001 RSI: ffffffff8aaabce0 RDI: ffffffff8afc6f80
RBP: ffffffff8ca07eb8 R08: ffff8880b8e36b2b R09: 1ffff110171c6d65
R10: dffffc0000000000 R11: ffffed10171c6d66 R12: ffffffff8e4a93e8
R13: 0000000000000000 R14: 0000000000000000 R15: 1ffffffff1952688
FS: 0000000000000000(0000) GS:ffff8880b8e00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fdcdea34f98 CR3: 0000000068115000 CR4: 00000000003506f0
Call Trace:
<TASK>
arch_safe_halt arch/x86/include/asm/paravirt.h:108 [inline]
default_idle+0x13/0x20 arch/x86/kernel/process.c:753
default_idle_call+0x6c/0xa0 kernel/sched/idle.c:97
cpuidle_idle_call kernel/sched/idle.c:170 [inline]
do_idle+0x1eb/0x510 kernel/sched/idle.c:282
cpu_startup_entry+0x43/0x60 kernel/sched/idle.c:380
rest_init+0x2e2/0x300 init/main.c:744
arch_call_rest_init+0xe/0x10 init/main.c:841
start_kernel+0x459/0x4e0 init/main.c:1086
x86_64_start_reservations+0x2a/0x30 arch/x86/kernel/head64.c:555
x86_64_start_kernel+0x60/0x60 arch/x86/kernel/head64.c:536
secondary_startup_64_no_verify+0x179/0x17b
</TASK>


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