bisecting fixing commit since ef244c3088856cf048c77231653b4c92a7b2213c
building syzkaller on a41ca8fa8285754d8561dcc3ed54cca2da60eed7
testing commit ef244c3088856cf048c77231653b4c92a7b2213c with gcc (GCC) 8.1.0
kernel signature: 04191757b064a375f8882e35e2cb48706827adbd6576730bde293573211564b8
run #0: crashed: INFO: rcu detected stall in sys_open
run #1: crashed: INFO: rcu detected stall in corrupted
run #2: crashed: INFO: rcu detected stall in sys_open
run #3: crashed: INFO: rcu detected stall in ext4_file_read_iter
run #4: crashed: INFO: rcu detected stall in sys_open
run #5: crashed: INFO: rcu detected stall in sys_open
run #6: crashed: INFO: rcu detected stall in ext4_file_read_iter
run #7: crashed: INFO: rcu detected stall in sys_open
run #8: crashed: INFO: rcu detected stall in sys_open
run #9: crashed: INFO: rcu detected stall in corrupted
testing current HEAD b94de4d19498b454645b72d08a05d32fa9074fb5
testing commit b94de4d19498b454645b72d08a05d32fa9074fb5 with gcc (GCC) 8.1.0
kernel signature: 6528e607700559e6721fa6b2ff6a5745856d5bfab9f21d57e6d8553ca8f58a4b
run #0: crashed: INFO: rcu detected stall in sys_open
run #1: crashed: INFO: rcu detected stall in corrupted
run #2: crashed: INFO: rcu detected stall in ext4_file_read_iter
run #3: crashed: INFO: rcu detected stall in ext4_file_read_iter
run #4: crashed: INFO: rcu detected stall in sys_open
run #5: crashed: INFO: rcu detected stall in sys_open
run #6: crashed: INFO: rcu detected stall in corrupted
run #7: crashed: INFO: rcu detected stall in ext4_file_read_iter
run #8: crashed: INFO: rcu detected stall in sys_open
run #9: crashed: INFO: rcu detected stall in sys_open
revisions tested: 2, total time: 29m8.474235704s (build: 17m12.76412991s, test: 10m58.816990227s)
the crash still happens on HEAD
commit msg: Linux 4.19.155
crash: INFO: rcu detected stall in sys_open
audit: type=1800 audit(1604848424.874:28): pid=7384 uid=0 auid=0 ses=8 subj==unconfined op=collect_data cause=failed comm="syz-executor.1" name="bus" dev="sda1" ino=15771 res=0
audit: type=1800 audit(1604848425.054:29): pid=7389 uid=0 auid=0 ses=8 subj==unconfined op=collect_data cause=failed comm="syz-executor.5" name="bus" dev="sda1" ino=15802 res=0
rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 	(detected by 0, t=10502 jiffies, g=5477, q=22668)
rcu: All QSes seen, last rcu_preempt kthread activity 10503 (4294965619-4294955116), jiffies_till_next_fqs=1, root ->qsmask 0x0
syz-executor.3  R  running task    21784  7411   6352 0x80000000
Call Trace:
 <IRQ>
 sched_show_task.cold.86+0x2ee/0x35d kernel/sched/core.c:5341
 print_other_cpu_stall kernel/rcu/tree.c:1430 [inline]
 check_cpu_stall kernel/rcu/tree.c:1557 [inline]
 __rcu_pending kernel/rcu/tree.c:3293 [inline]
 rcu_pending kernel/rcu/tree.c:3336 [inline]
 rcu_check_callbacks.cold.81+0xa80/0xd67 kernel/rcu/tree.c:2682
 update_process_times+0x28/0x90 kernel/time/timer.c:1650
 tick_sched_handle+0x77/0x140 kernel/time/tick-sched.c:168
 tick_sched_timer+0x37/0xf0 kernel/time/tick-sched.c:1278
 __run_hrtimer kernel/time/hrtimer.c:1401 [inline]
 __hrtimer_run_queues+0x2f7/0xab0 kernel/time/hrtimer.c:1463
 hrtimer_interrupt+0x2df/0x760 kernel/time/hrtimer.c:1521
 local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1067 [inline]
 smp_apic_timer_interrupt+0x114/0x540 arch/x86/kernel/apic/apic.c:1092
 apic_timer_interrupt+0xf/0x20 arch/x86/entry/entry_64.S:894
 </IRQ>
RIP: 0010:loop0+0x33/0x3f
Code: c5 fe 6f 56 40 c5 fe 6f 5e 60 c4 c2 7d 00 c5 c4 c2 75 00 cd c4 c2 6d 00 d5 c4 c2 65 00 dd c4 e3 7d 46 e2 20 c4 e3 7d 46 ea 31 <c4> e3 75 46 f3 20 c4 e3 75 46 fb 31 48 83 c6 40 48 89 b4 24 08 02
RSP: 0018:ffff8880a5f87220 EFLAGS: 00000283 ORIG_RAX: ffffffffffffff13
RAX: 00000000aa3f042a RBX: 000000004e58a951 RCX: 000000007810771f
RDX: 00000000630f9a3f RSI: ffff888095090b00 RDI: ffff8880a5f87570
RBP: ffff8880a5f874b0 R08: 00000000691c29e8 R09: 0000000003a09c2c
R10: 00000000b9a9a259 R11: 000000006566e30d R12: 0000000062514888
R13: 00000000999ee191 R14: 0000000065d77021 R15: 000000001ce1cab6
 sha256_avx2_update+0x10/0x20 arch/x86/crypto/sha256_ssse3_glue.c:235
 crypto_shash_update+0xd0/0x2e0 crypto/shash.c:126
 ima_calc_file_hash_tfm security/integrity/ima/ima_crypto.c:373 [inline]
 ima_calc_file_shash security/integrity/ima/ima_crypto.c:393 [inline]
 ima_calc_file_hash+0x51a/0x800 security/integrity/ima/ima_crypto.c:458
 ima_collect_measurement+0x3fc/0x520 security/integrity/ima/ima_api.c:231
 process_measurement+0xb0e/0x14b0 security/integrity/ima/ima_main.c:284
 ima_file_check+0xc8/0x110 security/integrity/ima/ima_main.c:391
 do_last fs/namei.c:3425 [inline]
 path_openat+0x746/0x3c60 fs/namei.c:3537
 do_filp_open+0x177/0x250 fs/namei.c:3567
 do_sys_open+0x1dd/0x350 fs/open.c:1085
 __do_sys_open fs/open.c:1103 [inline]
 __se_sys_open fs/open.c:1098 [inline]
 __x64_sys_open+0x79/0xb0 fs/open.c:1098
 do_syscall_64+0xd0/0x4e0 arch/x86/entry/common.c:293
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x459fc9
Code: 2d b6 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 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 fb b5 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007ffa14c00c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000002
RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 0000000000459fc9
RDX: 0000000000000000 RSI: 0000000000141042 RDI: 0000000020000100
RBP: 000000000075bf20 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007ffa14c016d4
R13: 00000000004fa7ff R14: 00000000004dc210 R15: 00000000ffffffff
rcu: rcu_preempt kthread starved for 10545 jiffies! g5477 f0x2 RCU_GP_WAIT_FQS(5) ->state=0x0 ->cpu=0
rcu: RCU grace-period kthread stack dump:
rcu_preempt     R  running task    29208    10      2 0x80000000
Call Trace:
 context_switch kernel/sched/core.c:2828 [inline]
 __schedule+0x78c/0x1c10 kernel/sched/core.c:3517
 schedule+0x7f/0x1b0 kernel/sched/core.c:3561
 schedule_timeout+0x3ab/0xe00 kernel/time/timer.c:1825
 rcu_gp_kthread+0xce6/0x23d0 kernel/rcu/tree.c:2202
 kthread+0x347/0x410 kernel/kthread.c:259
 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:415