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

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 3b9f64db0496 Linux 6.6.138
git tree: linux-6.6.y
console output: https://syzkaller.appspot.com/x/log.txt?x=12849636580000
kernel config: https://syzkaller.appspot.com/x/.config?x=c5b35c4db8465904
dashboard link: https://syzkaller.appspot.com/bug?extid=fafd6e32afaaa86f491e
compiler: Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=1633ead2580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/9e5afbe648d5/disk-3b9f64db.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/c3607dd9b93c/vmlinux-3b9f64db.xz
kernel image: https://storage.googleapis.com/syzbot-assets/f0392d8b3ded/bzImage-3b9f64db.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+fafd6e...@syzkaller.appspotmail.com

rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: Tasks blocked on level-0 rcu_node (CPUs 0-1): P5981/1:b..l
rcu: (detected by 1, t=10503 jiffies, g=12797, q=671 ncpus=2)
task:sed state:R running task stack:24232 pid:5981 ppid:5980 flags:0x00004002
Call Trace:
<TASK>
context_switch kernel/sched/core.c:5381 [inline]
__schedule+0x1553/0x45a0 kernel/sched/core.c:6700
preempt_schedule_irq+0xbf/0x150 kernel/sched/core.c:7010
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:debug_lockdep_rcu_enabled+0x20/0x30 kernel/rcu/update.c:320
Code: cc cc cc cc cc cc cc cc cc cc f3 0f 1e fa 31 c0 83 3d ef a9 04 04 00 74 1d 83 3d 76 dd 04 04 00 74 14 65 48 8b 0d c0 44 7d 75 <31> c0 83 b9 dc 0a 00 00 00 0f 94 c0 c3 cc cc cc 66 0f 1f 00 48 8b
RSP: 0018:ffffc90004abf638 EFLAGS: 00000202
RAX: 0000000000000000 RBX: ffff888018b48040 RCX: ffff888031000000
RDX: 0000000000000000 RSI: ffffffff8e7301d0 RDI: 0000000000000001
RBP: ffffc90004abf7f0 R08: ffff888031000000 R09: 0000000000000003
R10: 0000000000000002 R11: 0000000000000000 R12: ffff88802e959a80
R13: 00007fb46fd8afff R14: ffff88802e959ae0 R15: 00002a264a7d7000
mt_slot lib/maple_tree.c:814 [inline]
mas_slot lib/maple_tree.c:847 [inline]
mas_get_slot lib/maple_tree.c:6690 [inline]
mas_validate_gaps lib/maple_tree.c:6959 [inline]
mt_validate+0x262a/0x4400 lib/maple_tree.c:7234
validate_mm+0xc6/0x450 mm/mmap.c:288
vma_expand+0x5fe/0x920 mm/mmap.c:668
__mmap_region mm/mmap.c:2756 [inline]
mmap_region+0xbcc/0x2000 mm/mmap.c:2941
do_mmap+0x92c/0x10a0 mm/mmap.c:1385
vm_mmap_pgoff+0x1c4/0x3f0 mm/util.c:556
ksys_mmap_pgoff+0x520/0x700 mm/mmap.c:1431
do_syscall_x64 arch/x86/entry/common.c:46 [inline]
do_syscall_64+0x55/0xa0 arch/x86/entry/common.c:76
entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7fb47006b242
RSP: 002b:00007fff988a33e8 EFLAGS: 00000206 ORIG_RAX: 0000000000000009
RAX: ffffffffffffffda RBX: 00007fb46fd70000 RCX: 00007fb47006b242
RDX: 0000000000000001 RSI: 0000000000008000 RDI: 00007fb46fd70000
RBP: 0000000000000812 R08: 0000000000000003 R09: 0000000000024000
R10: 0000000000000812 R11: 0000000000000206 R12: 00007fff988a3470
R13: 00007fb470048ab0 R14: 00007fff988a3860 R15: 00000ffff3114680
</TASK>
rcu: rcu_preempt kthread starved for 10532 jiffies! g12797 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:27656 pid:17 ppid:2 flags:0x00004000
Call Trace:
<TASK>
context_switch kernel/sched/core.c:5381 [inline]
__schedule+0x1553/0x45a0 kernel/sched/core.c:6700
schedule+0xbd/0x170 kernel/sched/core.c:6774
schedule_timeout+0x188/0x2d0 kernel/time/timer.c:2168
rcu_gp_fqs_loop+0x313/0x1590 kernel/rcu/tree.c:1667
rcu_gp_kthread+0x9d/0x3b0 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:
CPU: 1 PID: 5985 Comm: syz.0.24 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/18/2026
RIP: 0010:__raw_spin_unlock_irq include/linux/spinlock_api_smp.h:160 [inline]
RIP: 0010:_raw_spin_unlock_irq+0x29/0x50 kernel/locking/spinlock.c:202
Code: 00 f3 0f 1e fa 53 48 89 fb 48 83 c7 18 48 8b 74 24 08 e8 ea 97 d8 f6 48 89 df e8 a2 6c d9 f6 e8 1d 7f fd f6 fb bf 01 00 00 00 <e8> 82 73 cc f6 65 8b 05 c3 a0 73 75 85 c0 74 02 5b c3 e8 40 88 70
RSP: 0018:ffffc90003487c78 EFLAGS: 00000286
RAX: a8c6e674c006c500 RBX: ffff88807b9ac0c0 RCX: a8c6e674c006c500
RDX: dffffc0000000000 RSI: ffffffff8acac9e0 RDI: 0000000000000001
RBP: ffff88807b9ac558 R08: ffffffff8e8b19af R09: 1ffffffff1d16335
R10: dffffc0000000000 R11: fffffbfff1d16336 R12: 1ffff1100f7358ab
R13: 0000000000000021 R14: dffffc0000000000 R15: 0000000000000000
FS: 00007f31ad17b6c0(0000) GS:ffff8880b8f00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000200000000058 CR3: 000000002ca88000 CR4: 00000000003506e0
Call Trace:
<TASK>
spin_unlock_irq include/linux/spinlock.h:401 [inline]
get_signal+0x11f5/0x13f0 kernel/signal.c:2905
arch_do_signal_or_restart+0xc2/0x800 arch/x86/kernel/signal.c:310
exit_to_user_mode_loop+0x70/0x110 kernel/entry/common.c:174
exit_to_user_mode_prepare+0xee/0x180 kernel/entry/common.c:210
__syscall_exit_to_user_mode_work kernel/entry/common.c:291 [inline]
syscall_exit_to_user_mode+0x1a/0x50 kernel/entry/common.c:302
do_syscall_64+0x61/0xa0 arch/x86/entry/common.c:82
entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f31ac39cdd7
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:00007f31ad17b0e8 EFLAGS: 00000246
RAX: 00000000000000ca RBX: 00007f31ac615fa8 RCX: 00007f31ac39cdd9
RDX: 0000000000000000 RSI: 0000000000000080 RDI: 00007f31ac615fa8
RBP: 00007f31ac615fa0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f31ac616038 R14: 00007ffcaf8f4a90 R15: 00007ffcaf8f4b78
</TASK>


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