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

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 60a9e718726f Linux 6.6.106
git tree: linux-6.6.y
console output: https://syzkaller.appspot.com/x/log.txt?x=16a20712580000
kernel config: https://syzkaller.appspot.com/x/.config?x=12606d4b8832c7e4
dashboard link: https://syzkaller.appspot.com/bug?extid=4e30383d917770460cb8
compiler: Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=10150c7c580000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=167dce42580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/eca27e056a5a/disk-60a9e718.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/bc64d4eeb7f6/vmlinux-60a9e718.xz
kernel image: https://storage.googleapis.com/syzbot-assets/a345041561ac/bzImage-60a9e718.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+4e3038...@syzkaller.appspotmail.com

rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: Tasks blocked on level-0 rcu_node (CPUs 0-1): P5988/1:b..l
rcu: (detected by 0, t=10503 jiffies, g=11869, q=737 ncpus=2)
task:dhcpcd-run-hook state:R running task stack:24232 pid:5988 ppid:5452 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:mas_is_none include/linux/maple_tree.h:507 [inline]
RIP: 0010:mt_validate_nulls lib/maple_tree.c:7199 [inline]
RIP: 0010:mt_validate+0x3e54/0x4530 lib/maple_tree.c:7235
Code: 00 4c 0f 44 e8 45 31 ff 31 ff 48 89 de e8 44 a9 29 f7 4d 09 f5 41 bc 01 00 00 00 eb 24 e8 f4 a4 29 f7 4c 8b 7c 24 38 41 fe c7 <48> 83 bc 24 d8 00 00 00 09 0f 84 c7 05 00 00 e8 d8 a4 29 f7 49 89
RSP: 0018:ffffc90003607760 EFLAGS: 00000207
RAX: ffffffff8a5beb4c RBX: ffff88802b2d5900 RCX: ffff88802ff70000
RDX: 0000000000000000 RSI: 000000000000000e RDI: 0000000000000005
RBP: ffffc90003607930 R08: ffff88802ff70000 R09: 0000000000000003
R10: 0000000000000003 R11: 0000000000000000 R12: 0000000000000005
R13: ffff88802c2e3680 R14: ffff88802c2e3600 R15: 0000000000000006
validate_mm+0xb1/0x420 mm/mmap.c:288
mmap_region+0xeaa/0x2020 mm/mmap.c:2947
do_mmap+0x92f/0x10a0 mm/mmap.c:1385
vm_mmap_pgoff+0x1c0/0x400 mm/util.c:556
ksys_mmap_pgoff+0x520/0x700 mm/mmap.c:1431
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: 0033:0x7ff93e726242
RSP: 002b:00007fff1de10178 EFLAGS: 00000246 ORIG_RAX: 0000000000000009
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007ff93e726242
RDX: 0000000000000001 RSI: 000000000002f6d0 RDI: 0000000000000000
RBP: 0000000000000802 R08: 0000000000000003 R09: 0000000000000000
R10: 0000000000000802 R11: 0000000000000246 R12: 0000000000000000
R13: 00007ff93e703ab0 R14: 00007fff1de105f0 R15: 00000fffe3bc2032
</TASK>
rcu: rcu_preempt kthread starved for 10530 jiffies! g11869 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:27752 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:
CPU: 0 PID: 5989 Comm: syz.2.19 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/18/2025
RIP: 0010:__might_sleep+0x35/0xe0 kernel/sched/core.c:10131
Code: 53 49 bf 00 00 00 00 00 fc ff df 65 48 8b 1d b2 90 a6 7e 4c 8d 73 18 4c 89 f0 48 c1 e8 03 42 0f b6 04 38 84 c0 75 78 41 8b 2e <85> ed 74 3a 48 81 c3 68 17 00 00 48 89 d8 48 c1 e8 03 42 80 3c 38
RSP: 0018:ffffc90002e57b98 EFLAGS: 00000246
RAX: 0000000000000000 RBX: ffff8880220dda00 RCX: 0000000000000000
RDX: ffff8880220dda00 RSI: 00000000000000a7 RDI: ffffffff8aa9e240
RBP: 0000000000000000 R08: ffffc90002e57e2f R09: 1ffff920005cafc5
R10: dffffc0000000000 R11: fffff520005cafc6 R12: dffffc0000000000
R13: dffffc0000000000 R14: ffff8880220dda18 R15: dffffc0000000000
FS: 00007f401e7e36c0(0000) GS:ffff8880b8e00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000200000000058 CR3: 0000000072c4f000 CR4: 00000000003506f0
Call Trace:
<TASK>
__might_fault+0x71/0x120 mm/memory.c:5944
__clear_user arch/x86/include/asm/uaccess_64.h:167 [inline]
clear_user arch/x86/include/asm/uaccess_64.h:191 [inline]
copy_siginfo_to_user+0x5b/0xa0 kernel/signal.c:3374
x64_setup_rt_frame+0x740/0xcd0 arch/x86/kernel/signal_64.c:194
setup_rt_frame arch/x86/kernel/signal.c:223 [inline]
handle_signal arch/x86/kernel/signal.c:267 [inline]
arch_do_signal_or_restart+0x3e5/0x780 arch/x86/kernel/signal.c:312
exit_to_user_mode_loop+0x70/0x110 kernel/entry/common.c:174
exit_to_user_mode_prepare+0xf6/0x180 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+0x61/0xb0 arch/x86/entry/common.c:87
entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f401d98eba7
Code: ff ff 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
RSP: 002b:00007f401e7e30e8 EFLAGS: 00000246
RAX: 00000000000000ca RBX: 00007f401dbd5fa8 RCX: 00007f401d98eba9
RDX: 0000000000000000 RSI: 0000000000000080 RDI: 00007f401dbd5fa8
RBP: 00007f401dbd5fa0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f401dbd6038 R14: 00007ffde676c4e0 R15: 00007ffde676c5c8
</TASK>


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