INFO: rcu detected stall in sys_open (2)

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit: b9d3d014 Add linux-next specific files for 20191122
git tree: linux-next
console output: https://syzkaller.appspot.com/x/log.txt?x=116ea322e00000
kernel config: https://syzkaller.appspot.com/x/.config?x=6c24c45ce29b175c
dashboard link: https://syzkaller.appspot.com/bug?extid=7ee926c5e237e614ccb1
compiler: gcc (GCC) 9.0.0 20181231 (experimental)
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=14e23986e00000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=11d6ad02e00000

Bisection is inconclusive: the first bad commit could be any of:

8ec426c7 lustre: don't set f_version in ll_readdir
ac0bf025 ima: Use i_version only when filesystem supports it
7a11ac28 ntfs: remove i_version handling

bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=13b9509ce00000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+7ee926...@syzkaller.appspotmail.com

rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
(detected by 0, t=10502 jiffies, g=7137, q=12)
rcu: All QSes seen, last rcu_preempt kthread activity 10502
(4295014020-4295003518), jiffies_till_next_fqs=1, root ->qsmask 0x0
syz-executor935 R running task 23704 8896 8886 0x80004000
Call Trace:
<IRQ>
sched_show_task kernel/sched/core.c:5954 [inline]
sched_show_task.cold+0x2ed/0x34e kernel/sched/core.c:5929
print_other_cpu_stall kernel/rcu/tree_stall.h:410 [inline]
check_cpu_stall kernel/rcu/tree_stall.h:538 [inline]
rcu_pending kernel/rcu/tree.c:2827 [inline]
rcu_sched_clock_irq.cold+0xaf4/0xc02 kernel/rcu/tree.c:2271
update_process_times+0x2d/0x70 kernel/time/timer.c:1726
tick_sched_handle+0xa2/0x190 kernel/time/tick-sched.c:167
tick_sched_timer+0x53/0x140 kernel/time/tick-sched.c:1310
__run_hrtimer kernel/time/hrtimer.c:1517 [inline]
__hrtimer_run_queues+0x364/0xe40 kernel/time/hrtimer.c:1579
hrtimer_interrupt+0x314/0x770 kernel/time/hrtimer.c:1641
local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1110 [inline]
smp_apic_timer_interrupt+0x160/0x610 arch/x86/kernel/apic/apic.c:1135
apic_timer_interrupt+0xf/0x20 arch/x86/entry/entry_64.S:829
</IRQ>
RIP: 0010:loop2+0x1e5/0x39e
Code: 63 7b f0 f0 06 41 21 c7 45 31 f5 c4 63 7b f0 e2 0d 41 31 cf c4 63 7b
f0 f2 16 89 d6 45 31 e6 c4 63 7b f0 e2 02 44 03 44 3c 20 <44> 09 d6 45 31
e6 41 89 d4 44 21 ce 45 21 d4 45 01 ef 45 01 c3 44
RSP: 0018:ffff88809dacf080 EFLAGS: 00000a17 ORIG_RAX: ffffffffffffff13
RAX: 000000000d895faf RBX: 00000000af692001 RCX: 00000000c2b12cbe
RDX: 00000000398a2513 RSI: 00000000398a2513 RDI: 00000000000001c0
RBP: ffff88809dacf318 R08: 0000000023af5072 R09: 00000000d9fb4f71
R10: 00000000449125ce R11: 00000000c47f205e R12: 00000000ce628944
R13: 000000008d7843d3 R14: 00000000000d80b7 R15: 00000000cf392011
sha256_avx2_update+0x2d/0x40 arch/x86/crypto/sha256_ssse3_glue.c:236
crypto_shash_update+0xc9/0x120 crypto/shash.c:120
ima_calc_file_hash_tfm+0x321/0x3e0 security/integrity/ima/ima_crypto.c:369
ima_calc_file_shash security/integrity/ima/ima_crypto.c:389 [inline]
ima_calc_file_hash+0x1aa/0x570 security/integrity/ima/ima_crypto.c:454
ima_collect_measurement+0x534/0x5f0 security/integrity/ima/ima_api.c:247
process_measurement+0xd45/0x1850 security/integrity/ima/ima_main.c:326
ima_file_check+0xc5/0x110 security/integrity/ima/ima_main.c:442
do_last fs/namei.c:3416 [inline]
path_openat+0x113d/0x4710 fs/namei.c:3529
do_filp_open+0x1a1/0x280 fs/namei.c:3559
do_sys_open+0x3fe/0x5d0 fs/open.c:1097
__do_sys_open fs/open.c:1115 [inline]
__se_sys_open fs/open.c:1110 [inline]
__x64_sys_open+0x7e/0xc0 fs/open.c:1110
do_syscall_64+0xfa/0x790 arch/x86/entry/common.c:294
entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x447709
Code: e8 3c e6 ff ff 48 83 c4 18 c3 0f 1f 80 00 00 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 0f 83 ab 06 fc ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007fce7ac54db8 EFLAGS: 00000246 ORIG_RAX: 0000000000000002
RAX: ffffffffffffffda RBX: 00000000006ddc28 RCX: 0000000000447709
RDX: 0000000000000000 RSI: 0000000000141042 RDI: 0000000020000100
RBP: 00000000006ddc20 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000006ddc2c
R13: 00007ffd0e67ecaf R14: 00007fce7ac559c0 R15: 0000000000000000
rcu: rcu_preempt kthread starved for 10502 jiffies! g7137 f0x2
RCU_GP_WAIT_FQS(5) ->state=0x0 ->cpu=1
rcu: RCU grace-period kthread stack dump:
rcu_preempt R running task 29272 10 2 0x80004000
Call Trace:
context_switch kernel/sched/core.c:3385 [inline]
__schedule+0x8e1/0x1f30 kernel/sched/core.c:4081
schedule+0xdc/0x2b0 kernel/sched/core.c:4155
schedule_timeout+0x486/0xc50 kernel/time/timer.c:1895
rcu_gp_fqs_loop kernel/rcu/tree.c:1661 [inline]
rcu_gp_kthread+0x9b2/0x18d0 kernel/rcu/tree.c:1821
kthread+0x361/0x430 kernel/kthread.c:255
ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:352


---
This bug is generated by a bot. It may contain errors.
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syzbot will keep track of this bug report. See:
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For information about bisection process see: https://goo.gl/tpsmEJ#bisection
syzbot can test patches for this bug, for details see:
https://goo.gl/tpsmEJ#testing-patches

[syzbot]

syzbot suspects this issue was fixed by commit:

commit 1d0e850a49a5b56f8f3cb51e74a11e2fedb96be6
Author: David Howells <dhow...@redhat.com>
Date: Fri Oct 16 12:21:14 2020 +0000

afs: Fix cell removal

bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=128ceadf500000
start commit: c85fb28b Merge tag 'arm64-fixes' of git://git.kernel.org/p..
git tree: upstream
kernel config: https://syzkaller.appspot.com/x/.config?x=de7f697da23057c7
dashboard link: https://syzkaller.appspot.com/bug?extid=7ee926c5e237e614ccb1
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=1227c177900000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=13553f60500000

If the result looks correct, please mark the issue as fixed by replying with:

#syz fix: afs: Fix cell removal

[Dmitry Vyukov]