Re: [syzbot] [mm?] INFO: rcu detected stall in mas_preallocate (2)

[syzbot <syzbot+882589c97d51a9de68eb@syzkaller.appspotmail.com>]

Hello,

syzbot has tested the proposed patch but the reproducer is still triggering an issue:
INFO: rcu detected stall in corrupted

rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 	(detected by 0, t=12997 jiffies, g=15009, q=2022 ncpus=2)
rcu: All QSes seen, last rcu_preempt kthread activity 12997 (4294963490-4294950493), jiffies_till_next_fqs=1, root ->qsmask 0x0
rcu: rcu_preempt kthread starved for 12997 jiffies! g15009 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:25624 pid:17    tgid:17    ppid:2      flags:0x00004000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5369 [inline]
 __schedule+0x1850/0x4c30 kernel/sched/core.c:6756
 __schedule_loop kernel/sched/core.c:6833 [inline]
 schedule+0x14b/0x320 kernel/sched/core.c:6848
 schedule_timeout+0x15a/0x290 kernel/time/sleep_timeout.c:99
 rcu_gp_fqs_loop+0x2df/0x1330 kernel/rcu/tree.c:2045
 rcu_gp_kthread+0xa7/0x3b0 kernel/rcu/tree.c:2247
 kthread+0x2f0/0x390 kernel/kthread.c:389
 ret_from_fork+0x4b/0x80 arch/x86/kernel/process.c:147
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244
 </TASK>
rcu: Stack dump where RCU GP kthread last ran:
CPU: 0 UID: 0 PID: 6541 Comm: syz-executor Not tainted 6.13.0-rc1-syzkaller-00172-g6e165f544379 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/13/2024
RIP: 0010:lock_acquire+0x264/0x550 kernel/locking/lockdep.c:5853
Code: 2b 00 74 08 4c 89 f7 e8 8a 0a 8b 00 f6 44 24 61 02 0f 85 85 01 00 00 41 f7 c7 00 02 00 00 74 01 fb 48 c7 44 24 40 0e 36 e0 45 <4b> c7 44 25 00 00 00 00 00 43 c7 44 25 09 00 00 00 00 43 c7 44 25
RSP: 0018:ffffc900042ff080 EFLAGS: 00000206
RAX: 0000000000000001 RBX: 1ffff9200085fe1c RCX: ffff888025bf8ad8
RDX: dffffc0000000000 RSI: ffffffff8c0aa9a0 RDI: ffffffff8c5f98c0
RBP: ffffc900042ff1d8 R08: ffffffff942a0887 R09: 1ffffffff2854110
R10: dffffc0000000000 R11: fffffbfff2854111 R12: 1ffff9200085fe18
R13: dffffc0000000000 R14: ffffc900042ff0e0 R15: 0000000000000246
FS:  0000000000000000(0000) GS:ffff8880b8600000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fe0e0053440 CR3: 000000002d710000 CR4: 00000000003526f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <IRQ>
 </IRQ>
 <TASK>
 rcu_lock_acquire include/linux/rcupdate.h:337 [inline]
 rcu_read_lock include/linux/rcupdate.h:849 [inline]
 page_ext_get+0x3d/0x2a0 mm/page_ext.c:525
 page_table_check_clear+0x4b/0x550 mm/page_table_check.c:74
 get_and_clear_full_ptes include/linux/pgtable.h:712 [inline]
 zap_present_folio_ptes mm/memory.c:1510 [inline]
 zap_present_ptes mm/memory.c:1595 [inline]
 do_zap_pte_range mm/memory.c:1697 [inline]
 zap_pte_range mm/memory.c:1739 [inline]
 zap_pmd_range mm/memory.c:1822 [inline]
 zap_pud_range mm/memory.c:1851 [inline]
 zap_p4d_range mm/memory.c:1872 [inline]
 unmap_page_range+0x376a/0x48d0 mm/memory.c:1893
 unmap_vmas+0x3cc/0x5f0 mm/memory.c:1983
 exit_mmap+0x288/0xd50 mm/mmap.c:1263
 __mmput+0x115/0x3c0 kernel/fork.c:1406
 exit_mm+0x220/0x310 kernel/exit.c:570
 do_exit+0x9b2/0x28e0 kernel/exit.c:925
 do_group_exit+0x207/0x2c0 kernel/exit.c:1087
 get_signal+0x16b2/0x1750 kernel/signal.c:3017
 arch_do_signal_or_restart+0x96/0x860 arch/x86/kernel/signal.c:337
 exit_to_user_mode_loop kernel/entry/common.c:111 [inline]
 exit_to_user_mode_prepare include/linux/entry-common.h:329 [inline]
 __syscall_exit_to_user_mode_work kernel/entry/common.c:207 [inline]
 syscall_exit_to_user_mode+0xce/0x340 kernel/entry/common.c:218
 do_syscall_64+0x100/0x230 arch/x86/entry/common.c:89
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f479f176197
Code: Unable to access opcode bytes at 0x7f479f17616d.
RSP: 002b:00007fffa52fadc0 EFLAGS: 00000293 ORIG_RAX: 000000000000003d
RAX: fffffffffffffe00 RBX: 000000000000199b RCX: 00007f479f176197
RDX: 0000000040000000 RSI: 00007fffa52fadfc RDI: 00000000ffffffff
RBP: 00007fffa52fadfc R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000293 R12: 00007fffa52fae80
R13: 00007fffa52fae88 R14: 0000000000000009 R15: 0000000000000000
 </TASK>


Tested on:

commit:         6e165f54 mm/page_isolation: fixup isolate_single_pageb..
git tree:       git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm mm-unstable
console output: https://syzkaller.appspot.com/x/log.txt?x=1571d4df980000
kernel config:  https://syzkaller.appspot.com/x/.config?x=6da4e19788a025a7
dashboard link: https://syzkaller.appspot.com/bug?extid=882589c97d51a9de68eb
compiler:       Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40

Note: no patches were applied.