INFO: task hung in fuse_simple_request

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syzbot

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Dec 13, 2020, 4:13:11 PM12/13/20
to linux-...@vger.kernel.org, linux-...@vger.kernel.org, mik...@szeredi.hu, syzkall...@googlegroups.com
Hello,

syzbot found the following issue on:

HEAD commit: 7b1b868e Merge tag 'for-linus' of git://git.kernel.org/pub..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=17e17137500000
kernel config: https://syzkaller.appspot.com/x/.config?x=3416bb960d5c705d
dashboard link: https://syzkaller.appspot.com/bug?extid=46fe899420456e014d6b
compiler: gcc (GCC) 10.1.0-syz 20200507

Unfortunately, I don't have any reproducer for this issue yet.

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+46fe89...@syzkaller.appspotmail.com

INFO: task syz-executor.0:12044 blocked for more than 143 seconds.
Not tainted 5.10.0-rc7-syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz-executor.0 state:D stack:28152 pid:12044 ppid: 8506 flags:0x00004004
Call Trace:
context_switch kernel/sched/core.c:3779 [inline]
__schedule+0x893/0x2130 kernel/sched/core.c:4528
schedule+0xcf/0x270 kernel/sched/core.c:4606
request_wait_answer+0x552/0x840 fs/fuse/dev.c:411
__fuse_request_send fs/fuse/dev.c:430 [inline]
fuse_simple_request+0x58a/0xd10 fs/fuse/dev.c:515
fuse_do_getattr+0x243/0xcb0 fs/fuse/dir.c:1029
fuse_update_get_attr fs/fuse/dir.c:1065 [inline]
fuse_getattr+0x3b0/0x470 fs/fuse/dir.c:1801
vfs_getattr_nosec+0x246/0x2e0 fs/stat.c:87
vfs_getattr fs/stat.c:124 [inline]
vfs_statx+0x18d/0x390 fs/stat.c:189
vfs_fstatat fs/stat.c:207 [inline]
vfs_stat include/linux/fs.h:3121 [inline]
__do_sys_newstat+0x91/0x110 fs/stat.c:349
do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46
entry_SYSCALL_64_after_hwframe+0x44/0xa9
RIP: 0033:0x45e159
RSP: 002b:00007f57f2e19c68 EFLAGS: 00000246 ORIG_RAX: 0000000000000004
RAX: ffffffffffffffda RBX: 0000000000000002 RCX: 000000000045e159
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 00000000200004c0
RBP: 000000000119bfb8 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 000000000119bf8c
R13: 00000000016afb7f R14: 00007f57f2e1a9c0 R15: 000000000119bf8c

Showing all locks held in the system:
2 locks held by kworker/u4:0/8:
#0: ffff8880b9e34998 (&rq->lock){-.-.}-{2:2}, at: rq_lock kernel/sched/sched.h:1292 [inline]
#0: ffff8880b9e34998 (&rq->lock){-.-.}-{2:2}, at: __schedule+0x21a/0x2130 kernel/sched/core.c:4446
#1: ffff8880b9e20048 (&per_cpu_ptr(group->pcpu, cpu)->seq){-.-.}-{0:0}, at: psi_task_switch+0x305/0x440 kernel/sched/psi.c:833
2 locks held by kworker/1:1/34:
#0: ffff888010066538 ((wq_completion)rcu_gp){+.+.}-{0:0}, at: arch_atomic64_set arch/x86/include/asm/atomic64_64.h:34 [inline]
#0: ffff888010066538 ((wq_completion)rcu_gp){+.+.}-{0:0}, at: atomic64_set include/asm-generic/atomic-instrumented.h:856 [inline]
#0: ffff888010066538 ((wq_completion)rcu_gp){+.+.}-{0:0}, at: atomic_long_set include/asm-generic/atomic-long.h:41 [inline]
#0: ffff888010066538 ((wq_completion)rcu_gp){+.+.}-{0:0}, at: set_work_data kernel/workqueue.c:616 [inline]
#0: ffff888010066538 ((wq_completion)rcu_gp){+.+.}-{0:0}, at: set_work_pool_and_clear_pending kernel/workqueue.c:643 [inline]
#0: ffff888010066538 ((wq_completion)rcu_gp){+.+.}-{0:0}, at: process_one_work+0x821/0x15a0 kernel/workqueue.c:2243
#1: ffffc90000e5fda8 ((work_completion)(&rew.rew_work)){+.+.}-{0:0}, at: process_one_work+0x854/0x15a0 kernel/workqueue.c:2247
3 locks held by kworker/u4:4/298:
#0: ffff888010069138 ((wq_completion)events_unbound){+.+.}-{0:0}, at: arch_atomic64_set arch/x86/include/asm/atomic64_64.h:34 [inline]
#0: ffff888010069138 ((wq_completion)events_unbound){+.+.}-{0:0}, at: atomic64_set include/asm-generic/atomic-instrumented.h:856 [inline]
#0: ffff888010069138 ((wq_completion)events_unbound){+.+.}-{0:0}, at: atomic_long_set include/asm-generic/atomic-long.h:41 [inline]
#0: ffff888010069138 ((wq_completion)events_unbound){+.+.}-{0:0}, at: set_work_data kernel/workqueue.c:616 [inline]
#0: ffff888010069138 ((wq_completion)events_unbound){+.+.}-{0:0}, at: set_work_pool_and_clear_pending kernel/workqueue.c:643 [inline]
#0: ffff888010069138 ((wq_completion)events_unbound){+.+.}-{0:0}, at: process_one_work+0x821/0x15a0 kernel/workqueue.c:2243
#1: ffffc90001aafda8 ((reaper_work).work){+.+.}-{0:0}, at: process_one_work+0x854/0x15a0 kernel/workqueue.c:2247
#2: ffff8880b9e34998 (&rq->lock){-.-.}-{2:2}, at: rq_lock kernel/sched/sched.h:1292 [inline]
#2: ffff8880b9e34998 (&rq->lock){-.-.}-{2:2}, at: __schedule+0x21a/0x2130 kernel/sched/core.c:4446
1 lock held by khungtaskd/1631:
#0: ffffffff8b3378e0 (rcu_read_lock){....}-{1:2}, at: debug_show_all_locks+0x53/0x260 kernel/locking/lockdep.c:6254
3 locks held by systemd-udevd/4897:
1 lock held by in:imklog/8170:
#0: ffff8880186bcaf0 (&f->f_pos_lock){+.+.}-{3:3}, at: __fdget_pos+0xe9/0x100 fs/file.c:932
1 lock held by syz-executor.0/8506:
#0: ffff888020e38458 (&xt[i].mutex){+.+.}-{3:3}, at: xt_find_table_lock+0x41/0x540 net/netfilter/x_tables.c:1206
1 lock held by syz-executor.1/8533:
#0: ffff888020e38d88 (&xt[i].mutex){+.+.}-{3:3}, at: xt_find_table_lock+0x41/0x540 net/netfilter/x_tables.c:1206
1 lock held by syz-executor.3/8756:
#0: ffff888020e38d88 (&xt[i].mutex){+.+.}-{3:3}, at: xt_find_table_lock+0x41/0x540 net/netfilter/x_tables.c:1206
2 locks held by syz-executor.4/8837:
#0: ffff888020e38d88 (&xt[i].mutex){+.+.}-{3:3}, at: xt_find_table_lock+0x41/0x540 net/netfilter/x_tables.c:1206
#1: ffffffff8b33ffa8 (rcu_state.exp_mutex){+.+.}-{3:3}, at: exp_funnel_lock kernel/rcu/tree_exp.h:290 [inline]
#1: ffffffff8b33ffa8 (rcu_state.exp_mutex){+.+.}-{3:3}, at: synchronize_rcu_expedited+0x4f2/0x610 kernel/rcu/tree_exp.h:836
2 locks held by syz-executor.2/10213:
#0: ffff888020e38458 (&xt[i].mutex){+.+.}-{3:3}, at: xt_find_table_lock+0x41/0x540 net/netfilter/x_tables.c:1206
#1: ffffffff8b33ffa8 (rcu_state.exp_mutex){+.+.}-{3:3}, at: exp_funnel_lock kernel/rcu/tree_exp.h:322 [inline]
#1: ffffffff8b33ffa8 (rcu_state.exp_mutex){+.+.}-{3:3}, at: synchronize_rcu_expedited+0x27e/0x610 kernel/rcu/tree_exp.h:836

=============================================

NMI backtrace for cpu 1
CPU: 1 PID: 1631 Comm: khungtaskd Not tainted 5.10.0-rc7-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
__dump_stack lib/dump_stack.c:77 [inline]
dump_stack+0x107/0x163 lib/dump_stack.c:118
nmi_cpu_backtrace.cold+0x44/0xd7 lib/nmi_backtrace.c:105
nmi_trigger_cpumask_backtrace+0x1b3/0x230 lib/nmi_backtrace.c:62
trigger_all_cpu_backtrace include/linux/nmi.h:146 [inline]
check_hung_uninterruptible_tasks kernel/hung_task.c:209 [inline]
watchdog+0xd43/0xfa0 kernel/hung_task.c:294
kthread+0x3b1/0x4a0 kernel/kthread.c:292
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:296
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 PID: 18218 Comm: syz-executor.0 Not tainted 5.10.0-rc7-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
RIP: 0010:unwind_next_frame+0x98/0x1f90 arch/x86/kernel/unwind_orc.c:618
Code: b6 04 02 84 c0 74 08 3c 03 0f 8e 54 0b 00 00 41 8b 2f 31 c0 85 ed 75 3b 48 ba 00 00 00 00 00 fc ff df 48 c7 04 13 00 00 00 00 <48> 8b 9c 24 98 00 00 00 65 48 2b 1c 25 28 00 00 00 0f 85 4a 16 00
RSP: 0000:ffffc900157af888 EFLAGS: 00000286
RAX: 0000000000000001 RBX: 1ffff92002af5f19 RCX: 0000000000000000
RDX: dffffc0000000000 RSI: ffffc900157afef8 RDI: 0000000000000001
RBP: ffffc900157aff28 R08: ffffffff8d62e65a R09: 0000000000000001
R10: 0000000000082081 R11: 0000000000000001 R12: ffffc900157a8000
R13: ffffc900157af995 R14: ffffc900157af9b0 R15: ffffc900157af960
FS: 000000000344a940(0000) GS:ffff8880b9e00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f57f2dd8d90 CR3: 0000000022b2a000 CR4: 00000000001506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
arch_stack_walk+0x7d/0xe0 arch/x86/kernel/stacktrace.c:25
stack_trace_save+0x8c/0xc0 kernel/stacktrace.c:121
kasan_save_stack+0x1b/0x40 mm/kasan/common.c:48
kasan_set_track mm/kasan/common.c:56 [inline]
__kasan_kmalloc.constprop.0+0xc2/0xd0 mm/kasan/common.c:461
slab_post_alloc_hook mm/slab.h:535 [inline]
slab_alloc_node mm/slub.c:2891 [inline]
slab_alloc mm/slub.c:2899 [inline]
kmem_cache_alloc+0x1c6/0x440 mm/slub.c:2904
anon_vma_chain_alloc mm/rmap.c:136 [inline]
__anon_vma_prepare+0x5d/0x560 mm/rmap.c:190
anon_vma_prepare include/linux/rmap.h:153 [inline]
do_anonymous_page mm/memory.c:3520 [inline]
handle_pte_fault mm/memory.c:4372 [inline]
__handle_mm_fault mm/memory.c:4509 [inline]
handle_mm_fault+0x87d/0x55d0 mm/memory.c:4607
do_user_addr_fault+0x55b/0xb40 arch/x86/mm/fault.c:1372
handle_page_fault arch/x86/mm/fault.c:1429 [inline]
exc_page_fault+0x9e/0x180 arch/x86/mm/fault.c:1485
asm_exc_page_fault+0x1e/0x30 arch/x86/include/asm/idtentry.h:583
RIP: 0033:0x41557f
Code: 0f 84 c8 02 00 00 48 83 bd 78 ff ff ff 00 0f 84 f9 04 00 00 48 8b 95 68 ff ff ff 44 89 95 38 ff ff ff 4c 8d ac 10 00 f7 ff ff <49> 89 85 90 06 00 00 49 8d 85 10 03 00 00 49 89 95 98 06 00 00 41
RSP: 002b:00000000016afb10 EFLAGS: 00010206
RAX: 00007f57f2db8000 RBX: 0000000000020000 RCX: 000000000045e1aa
RDX: 0000000000021000 RSI: 0000000000021000 RDI: 0000000000000000
RBP: 00000000016afbf0 R08: ffffffffffffffff R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000016afce0
R13: 00007f57f2dd8700 R14: 0000000000000003 R15: 000000000119c0dc


---
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syzbot

unread,
Jul 16, 2021, 10:28:22 PM7/16/21
to areeba...@futuregulfpak.com, linux-...@vger.kernel.org, linux-...@vger.kernel.org, mik...@szeredi.hu, syzkall...@googlegroups.com
syzbot has found a reproducer for the following issue on:

HEAD commit: d936eb238744 Revert "Makefile: Enable -Wimplicit-fallthrou..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=1492834a300000
kernel config: https://syzkaller.appspot.com/x/.config?x=73e52880ded966e4
dashboard link: https://syzkaller.appspot.com/bug?extid=46fe899420456e014d6b
compiler: Debian clang version 11.0.1-2
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=165fc902300000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=1130705c300000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+46fe89...@syzkaller.appspotmail.com

INFO: task syz-executor874:8578 blocked for more than 143 seconds.
Not tainted 5.14.0-rc1-syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz-executor874 state:D stack:26768 pid: 8578 ppid: 8450 flags:0x00004004
Call Trace:
context_switch kernel/sched/core.c:4683 [inline]
__schedule+0xc07/0x11f0 kernel/sched/core.c:5940
schedule+0x14b/0x210 kernel/sched/core.c:6019
request_wait_answer fs/fuse/dev.c:411 [inline]
__fuse_request_send fs/fuse/dev.c:430 [inline]
fuse_simple_request+0x1125/0x19f0 fs/fuse/dev.c:515
fuse_do_getattr+0x396/0x1210 fs/fuse/dir.c:1009
vfs_getattr fs/stat.c:142 [inline]
vfs_statx+0x1ba/0x3d0 fs/stat.c:207
vfs_fstatat fs/stat.c:225 [inline]
__do_sys_newfstatat fs/stat.c:394 [inline]
__se_sys_newfstatat+0xb4/0x780 fs/stat.c:388
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x3d/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x44/0xae
RIP: 0033:0x446039
RSP: 002b:00007fbb526242f8 EFLAGS: 00000246 ORIG_RAX: 0000000000000106
RAX: ffffffffffffffda RBX: 00000000004cb4e0 RCX: 0000000000446039
RDX: 0000000000000000 RSI: 00000000200000c0 RDI: ffffffffffffff9c
RBP: 000000000049b16c R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0030656c69662f2e
R13: 64695f70756f7267 R14: 65646f6d746f6f72 R15: 00000000004cb4e8
INFO: task syz-executor874:8582 blocked for more than 143 seconds.
Not tainted 5.14.0-rc1-syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz-executor874 state:D stack:25368 pid: 8582 ppid: 8451 flags:0x00004004
Call Trace:
context_switch kernel/sched/core.c:4683 [inline]
__schedule+0xc07/0x11f0 kernel/sched/core.c:5940
schedule+0x14b/0x210 kernel/sched/core.c:6019
request_wait_answer fs/fuse/dev.c:411 [inline]
__fuse_request_send fs/fuse/dev.c:430 [inline]
fuse_simple_request+0x1125/0x19f0 fs/fuse/dev.c:515
fuse_do_getattr+0x396/0x1210 fs/fuse/dir.c:1009
vfs_getattr fs/stat.c:142 [inline]
vfs_statx+0x1ba/0x3d0 fs/stat.c:207
vfs_fstatat fs/stat.c:225 [inline]
__do_sys_newfstatat fs/stat.c:394 [inline]
__se_sys_newfstatat+0xb4/0x780 fs/stat.c:388
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x3d/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x44/0xae
RIP: 0033:0x446039
RSP: 002b:00007fbb526242f8 EFLAGS: 00000246 ORIG_RAX: 0000000000000106
RAX: ffffffffffffffda RBX: 00000000004cb4e0 RCX: 0000000000446039
RDX: 0000000000000000 RSI: 00000000200000c0 RDI: ffffffffffffff9c
RBP: 000000000049b16c R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0030656c69662f2e
R13: 64695f70756f7267 R14: 65646f6d746f6f72 R15: 00000000004cb4e8
INFO: task syz-executor874:8597 blocked for more than 143 seconds.
Not tainted 5.14.0-rc1-syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz-executor874 state:D stack:24784 pid: 8597 ppid: 8448 flags:0x00004004
Call Trace:
context_switch kernel/sched/core.c:4683 [inline]
__schedule+0xc07/0x11f0 kernel/sched/core.c:5940
schedule+0x14b/0x210 kernel/sched/core.c:6019
request_wait_answer fs/fuse/dev.c:411 [inline]
__fuse_request_send fs/fuse/dev.c:430 [inline]
fuse_simple_request+0x1125/0x19f0 fs/fuse/dev.c:515
fuse_do_getattr+0x396/0x1210 fs/fuse/dir.c:1009
vfs_getattr fs/stat.c:142 [inline]
vfs_statx+0x1ba/0x3d0 fs/stat.c:207
vfs_fstatat fs/stat.c:225 [inline]
__do_sys_newfstatat fs/stat.c:394 [inline]
__se_sys_newfstatat+0xb4/0x780 fs/stat.c:388
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x3d/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x44/0xae
RIP: 0033:0x446039
RSP: 002b:00007fbb526242f8 EFLAGS: 00000246 ORIG_RAX: 0000000000000106
RAX: ffffffffffffffda RBX: 00000000004cb4e0 RCX: 0000000000446039
RDX: 0000000000000000 RSI: 00000000200000c0 RDI: ffffffffffffff9c
RBP: 000000000049b16c R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0030656c69662f2e
R13: 64695f70756f7267 R14: 65646f6d746f6f72 R15: 00000000004cb4e8
INFO: task syz-executor874:8601 blocked for more than 144 seconds.
Not tainted 5.14.0-rc1-syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz-executor874 state:D stack:24784 pid: 8601 ppid: 8452 flags:0x00004004
Call Trace:
context_switch kernel/sched/core.c:4683 [inline]
__schedule+0xc07/0x11f0 kernel/sched/core.c:5940
schedule+0x14b/0x210 kernel/sched/core.c:6019
request_wait_answer fs/fuse/dev.c:411 [inline]
__fuse_request_send fs/fuse/dev.c:430 [inline]
fuse_simple_request+0x1125/0x19f0 fs/fuse/dev.c:515
fuse_do_getattr+0x396/0x1210 fs/fuse/dir.c:1009
vfs_getattr fs/stat.c:142 [inline]
vfs_statx+0x1ba/0x3d0 fs/stat.c:207
vfs_fstatat fs/stat.c:225 [inline]
__do_sys_newfstatat fs/stat.c:394 [inline]
__se_sys_newfstatat+0xb4/0x780 fs/stat.c:388
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x3d/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x44/0xae
RIP: 0033:0x446039
RSP: 002b:00007fbb526242f8 EFLAGS: 00000246 ORIG_RAX: 0000000000000106
RAX: ffffffffffffffda RBX: 00000000004cb4e0 RCX: 0000000000446039
RDX: 0000000000000000 RSI: 00000000200000c0 RDI: ffffffffffffff9c
RBP: 000000000049b16c R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0030656c69662f2e
R13: 64695f70756f7267 R14: 65646f6d746f6f72 R15: 00000000004cb4e8
INFO: task syz-executor874:8617 blocked for more than 144 seconds.
Not tainted 5.14.0-rc1-syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz-executor874 state:D stack:26768 pid: 8617 ppid: 8451 flags:0x00004004
Call Trace:
context_switch kernel/sched/core.c:4683 [inline]
__schedule+0xc07/0x11f0 kernel/sched/core.c:5940
schedule+0x14b/0x210 kernel/sched/core.c:6019
request_wait_answer fs/fuse/dev.c:411 [inline]
__fuse_request_send fs/fuse/dev.c:430 [inline]
fuse_simple_request+0x1125/0x19f0 fs/fuse/dev.c:515
fuse_do_getattr+0x396/0x1210 fs/fuse/dir.c:1009
vfs_getattr fs/stat.c:142 [inline]
vfs_statx+0x1ba/0x3d0 fs/stat.c:207
vfs_fstatat fs/stat.c:225 [inline]
__do_sys_newfstatat fs/stat.c:394 [inline]
__se_sys_newfstatat+0xb4/0x780 fs/stat.c:388
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x3d/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x44/0xae
RIP: 0033:0x446039
RSP: 002b:00007fbb526242f8 EFLAGS: 00000246 ORIG_RAX: 0000000000000106
RAX: ffffffffffffffda RBX: 00000000004cb4e0 RCX: 0000000000446039
RDX: 0000000000000000 RSI: 00000000200000c0 RDI: ffffffffffffff9c
RBP: 000000000049b16c R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0030656c69662f2e
R13: 64695f70756f7267 R14: 65646f6d746f6f72 R15: 00000000004cb4e8
INFO: task syz-executor874:8626 blocked for more than 144 seconds.
Not tainted 5.14.0-rc1-syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz-executor874 state:D stack:24784 pid: 8626 ppid: 8450 flags:0x00004004
Call Trace:
context_switch kernel/sched/core.c:4683 [inline]
__schedule+0xc07/0x11f0 kernel/sched/core.c:5940
schedule+0x14b/0x210 kernel/sched/core.c:6019
request_wait_answer fs/fuse/dev.c:411 [inline]
__fuse_request_send fs/fuse/dev.c:430 [inline]
fuse_simple_request+0x1125/0x19f0 fs/fuse/dev.c:515
fuse_do_getattr+0x396/0x1210 fs/fuse/dir.c:1009
vfs_getattr fs/stat.c:142 [inline]
vfs_statx+0x1ba/0x3d0 fs/stat.c:207
vfs_fstatat fs/stat.c:225 [inline]
__do_sys_newfstatat fs/stat.c:394 [inline]
__se_sys_newfstatat+0xb4/0x780 fs/stat.c:388
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x3d/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x44/0xae
RIP: 0033:0x446039
RSP: 002b:00007fbb526242f8 EFLAGS: 00000246 ORIG_RAX: 0000000000000106
RAX: ffffffffffffffda RBX: 00000000004cb4e0 RCX: 0000000000446039
RDX: 0000000000000000 RSI: 00000000200000c0 RDI: ffffffffffffff9c
RBP: 000000000049b16c R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0030656c69662f2e
R13: 64695f70756f7267 R14: 65646f6d746f6f72 R15: 00000000004cb4e8
INFO: task syz-executor874:8630 blocked for more than 145 seconds.
Not tainted 5.14.0-rc1-syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz-executor874 state:D stack:24784 pid: 8630 ppid: 8452 flags:0x00004004
Call Trace:
context_switch kernel/sched/core.c:4683 [inline]
__schedule+0xc07/0x11f0 kernel/sched/core.c:5940
schedule+0x14b/0x210 kernel/sched/core.c:6019
request_wait_answer fs/fuse/dev.c:411 [inline]
__fuse_request_send fs/fuse/dev.c:430 [inline]
fuse_simple_request+0x1125/0x19f0 fs/fuse/dev.c:515
fuse_do_getattr+0x396/0x1210 fs/fuse/dir.c:1009
vfs_getattr fs/stat.c:142 [inline]
vfs_statx+0x1ba/0x3d0 fs/stat.c:207
vfs_fstatat fs/stat.c:225 [inline]
__do_sys_newfstatat fs/stat.c:394 [inline]
__se_sys_newfstatat+0xb4/0x780 fs/stat.c:388
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x3d/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x44/0xae
RIP: 0033:0x446039
RSP: 002b:00007fbb526242f8 EFLAGS: 00000246 ORIG_RAX: 0000000000000106
RAX: ffffffffffffffda RBX: 00000000004cb4e0 RCX: 0000000000446039
RDX: 0000000000000000 RSI: 00000000200000c0 RDI: ffffffffffffff9c
RBP: 000000000049b16c R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0030656c69662f2e
R13: 64695f70756f7267 R14: 65646f6d746f6f72 R15: 00000000004cb4e8
INFO: task syz-executor874:8634 blocked for more than 145 seconds.
Not tainted 5.14.0-rc1-syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz-executor874 state:D stack:26640 pid: 8634 ppid: 8448 flags:0x00004004
Call Trace:
context_switch kernel/sched/core.c:4683 [inline]
__schedule+0xc07/0x11f0 kernel/sched/core.c:5940
schedule+0x14b/0x210 kernel/sched/core.c:6019
request_wait_answer fs/fuse/dev.c:411 [inline]
__fuse_request_send fs/fuse/dev.c:430 [inline]
fuse_simple_request+0x1125/0x19f0 fs/fuse/dev.c:515
fuse_do_getattr+0x396/0x1210 fs/fuse/dir.c:1009
vfs_getattr fs/stat.c:142 [inline]
vfs_statx+0x1ba/0x3d0 fs/stat.c:207
vfs_fstatat fs/stat.c:225 [inline]
__do_sys_newfstatat fs/stat.c:394 [inline]
__se_sys_newfstatat+0xb4/0x780 fs/stat.c:388
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x3d/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x44/0xae
RIP: 0033:0x446039
RSP: 002b:00007fbb526242f8 EFLAGS: 00000246 ORIG_RAX: 0000000000000106
RAX: ffffffffffffffda RBX: 00000000004cb4e0 RCX: 0000000000446039
RDX: 0000000000000000 RSI: 00000000200000c0 RDI: ffffffffffffff9c
RBP: 000000000049b16c R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0030656c69662f2e
R13: 64695f70756f7267 R14: 65646f6d746f6f72 R15: 00000000004cb4e8
INFO: task syz-executor874:8657 blocked for more than 145 seconds.
Not tainted 5.14.0-rc1-syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz-executor874 state:D stack:26768 pid: 8657 ppid: 8450 flags:0x00004004
Call Trace:
context_switch kernel/sched/core.c:4683 [inline]
__schedule+0xc07/0x11f0 kernel/sched/core.c:5940
schedule+0x14b/0x210 kernel/sched/core.c:6019
request_wait_answer fs/fuse/dev.c:411 [inline]
__fuse_request_send fs/fuse/dev.c:430 [inline]
fuse_simple_request+0x1125/0x19f0 fs/fuse/dev.c:515
fuse_do_getattr+0x396/0x1210 fs/fuse/dir.c:1009
vfs_getattr fs/stat.c:142 [inline]
vfs_statx+0x1ba/0x3d0 fs/stat.c:207
vfs_fstatat fs/stat.c:225 [inline]
__do_sys_newfstatat fs/stat.c:394 [inline]
__se_sys_newfstatat+0xb4/0x780 fs/stat.c:388
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x3d/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x44/0xae
RIP: 0033:0x446039
RSP: 002b:00007fbb526242f8 EFLAGS: 00000246 ORIG_RAX: 0000000000000106
RAX: ffffffffffffffda RBX: 00000000004cb4e0 RCX: 0000000000446039
RDX: 0000000000000000 RSI: 00000000200000c0 RDI: ffffffffffffff9c
RBP: 000000000049b16c R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0030656c69662f2e
R13: 64695f70756f7267 R14: 65646f6d746f6f72 R15: 00000000004cb4e8
INFO: task syz-executor874:8665 blocked for more than 145 seconds.
Not tainted 5.14.0-rc1-syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz-executor874 state:D stack:26768 pid: 8665 ppid: 8452 flags:0x00004004
Call Trace:
context_switch kernel/sched/core.c:4683 [inline]
__schedule+0xc07/0x11f0 kernel/sched/core.c:5940
schedule+0x14b/0x210 kernel/sched/core.c:6019
request_wait_answer fs/fuse/dev.c:411 [inline]
__fuse_request_send fs/fuse/dev.c:430 [inline]
fuse_simple_request+0x1125/0x19f0 fs/fuse/dev.c:515
fuse_do_getattr+0x396/0x1210 fs/fuse/dir.c:1009
vfs_getattr fs/stat.c:142 [inline]
vfs_statx+0x1ba/0x3d0 fs/stat.c:207
vfs_fstatat fs/stat.c:225 [inline]
__do_sys_newfstatat fs/stat.c:394 [inline]
__se_sys_newfstatat+0xb4/0x780 fs/stat.c:388
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x3d/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x44/0xae
RIP: 0033:0x446039
RSP: 002b:00007fbb526242f8 EFLAGS: 00000246 ORIG_RAX: 0000000000000106
RAX: ffffffffffffffda RBX: 00000000004cb4e0 RCX: 0000000000446039
RDX: 0000000000000000 RSI: 00000000200000c0 RDI: ffffffffffffff9c
RBP: 000000000049b16c R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0030656c69662f2e
R13: 64695f70756f7267 R14: 65646f6d746f6f72 R15: 00000000004cb4e8

Showing all locks held in the system:
1 lock held by ksoftirqd/0/13:
#0: ffff8880b9c514d8 (&rq->__lock){-.-.}-{2:2}, at: raw_spin_rq_lock_nested+0x1b/0x30 kernel/sched/core.c:460
1 lock held by khungtaskd/1644:
#0: ffffffff8c7177c0 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire+0x0/0x30 arch/x86/pci/mmconfig_64.c:151
1 lock held by in:imklog/8138:
#0: ffff888019edb270 (&f->f_pos_lock){+.+.}-{3:3}, at: __fdget_pos+0x24e/0x2f0 fs/file.c:974
no locks held by syz-executor874/16040.

=============================================

NMI backtrace for cpu 1
CPU: 1 PID: 1644 Comm: khungtaskd Not tainted 5.14.0-rc1-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
__dump_stack lib/dump_stack.c:88 [inline]
dump_stack_lvl+0x1d3/0x29f lib/dump_stack.c:105
nmi_cpu_backtrace+0x16c/0x190 lib/nmi_backtrace.c:105
nmi_trigger_cpumask_backtrace+0x191/0x2f0 lib/nmi_backtrace.c:62
trigger_all_cpu_backtrace include/linux/nmi.h:146 [inline]
check_hung_uninterruptible_tasks kernel/hung_task.c:210 [inline]
watchdog+0xd06/0xd50 kernel/hung_task.c:295
kthread+0x453/0x480 kernel/kthread.c:319
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 PID: 8453 Comm: syz-executor874 Not tainted 5.14.0-rc1-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
RIP: 0010:put_pid+0x0/0x130 kernel/pid.c:106
Code: 1f 84 00 00 00 00 00 0f 1f 00 be af 00 00 00 48 c7 c7 40 99 5c 8c e8 ff d4 74 00 c3 cc cc cc cc cc cc cc cc cc cc cc cc cc cc <55> 41 57 41 56 41 54 53 49 89 ff e8 c0 a3 2b 00 4d 85 ff 0f 84 aa
RSP: 0018:ffffc9000198fc78 EFLAGS: 00000286
RAX: 0000000000000000 RBX: dffffc0000000000 RCX: 0000000000000001
RDX: dffffc0000000000 RSI: 0000000000000001 RDI: 0000000000000000
RBP: ffffc9000198fd90 R08: ffffffff81869020 R09: ffffed1002bf8685
R10: ffffed1002bf8685 R11: 0000000000000000 R12: 0000000000000000
R13: 1ffff92000331f94 R14: 1ffff92000331f9b R15: 0000000000000000
FS: 00000000020ba300(0000) GS:ffff8880b9c00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fbb52603718 CR3: 00000000366ee000 CR4: 00000000001506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
kernel_wait4+0x27f/0x380 kernel/exit.c:1678
__do_sys_wait4 kernel/exit.c:1705 [inline]
__se_sys_wait4 kernel/exit.c:1701 [inline]
__x64_sys_wait4+0x117/0x1c0 kernel/exit.c:1701
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x3d/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x44/0xae
RIP: 0033:0x444826
Code: 0f 1f 40 00 31 c9 e9 09 00 00 00 66 0f 1f 84 00 00 00 00 00 49 89 ca 64 8b 04 25 18 00 00 00 85 c0 75 11 b8 3d 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 5a c3 90 48 83 ec 28 89 54 24 14 48 89 74 24
RSP: 002b:00007fff50fbe958 EFLAGS: 00000246 ORIG_RAX: 000000000000003d
RAX: ffffffffffffffda RBX: 00007fff50fbea10 RCX: 0000000000444826
RDX: 0000000040000001 RSI: 00007fff50fbe98c RDI: 00000000ffffffff
RBP: 00007fff50fbe98c R08: 00007fff50fec080 R09: 0000000000000010
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000000f4240
R13: 0000000000001eee R14: 00007fff50fbe9e0 R15: 00007fff50fbe9d0

Miklos Szeredi

unread,
Aug 6, 2021, 4:54:17 AM8/6/21
to syzbot, syzbot, areeba...@futuregulfpak.com, linux-...@vger.kernel.org, linux-...@vger.kernel.org, syzkaller-bugs
Hi,

I'm not sure what to make of this report.

Does syzbot try to kill all tasks before generating such a hung task report?

Does it use the fuse specific /sys/fs/fuse/connections/*/abort to
terminate stuck filesystems?

Thanks,
Miklos

Dmitry Vyukov

unread,
Aug 6, 2021, 5:15:31 AM8/6/21
to Miklos Szeredi, syzbot, syzbot, areeba...@futuregulfpak.com, linux-...@vger.kernel.org, linux-...@vger.kernel.org, syzkaller-bugs
",On Fri, 6 Aug 2021 at 10:54, Miklos Szeredi <mik...@szeredi.hu> wrote:
>
> Hi,
>
> I'm not sure what to make of this report.
>
> Does syzbot try to kill all tasks before generating such a hung task report?
>
> Does it use the fuse specific /sys/fs/fuse/connections/*/abort to
> terminate stuck filesystems?

Hi Miklos,

Grepping the C reproducer for "/sys/fs/fuse/connections", it seems
that it tries to abort all connections.
> --
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Miklos Szeredi

unread,
Aug 6, 2021, 5:34:55 AM8/6/21
to Dmitry Vyukov, syzbot, syzbot, areeba...@futuregulfpak.com, linux-...@vger.kernel.org, linux-...@vger.kernel.org, syzkaller-bugs
On Fri, 6 Aug 2021 at 11:15, Dmitry Vyukov <dvy...@google.com> wrote:
>
> ",On Fri, 6 Aug 2021 at 10:54, Miklos Szeredi <mik...@szeredi.hu> wrote:
> >
> > Hi,
> >
> > I'm not sure what to make of this report.
> >
> > Does syzbot try to kill all tasks before generating such a hung task report?
> >
> > Does it use the fuse specific /sys/fs/fuse/connections/*/abort to
> > terminate stuck filesystems?
>
> Hi Miklos,
>
> Grepping the C reproducer for "/sys/fs/fuse/connections", it seems
> that it tries to abort all connections.

Hi Dmitry,

So this could indicate a bug in the abort code of fuse, or it could
indicate that the test case DoS-es the system so that the abort code
simply doesn't get the resources to execute.

Can the two be differentiated somehow?

Thanks,
Miklos

Dmitry Vyukov

unread,
Aug 6, 2021, 7:09:59 AM8/6/21
to Miklos Szeredi, syzbot, syzbot, areeba...@futuregulfpak.com, linux-...@vger.kernel.org, linux-...@vger.kernel.org, syzkaller-bugs
On Fri, 6 Aug 2021 at 11:34, Miklos Szeredi <mik...@szeredi.hu> wrote:
> > > Hi,
> > >
> > > I'm not sure what to make of this report.
> > >
> > > Does syzbot try to kill all tasks before generating such a hung task report?
> > >
> > > Does it use the fuse specific /sys/fs/fuse/connections/*/abort to
> > > terminate stuck filesystems?
> >
> > Hi Miklos,
> >
> > Grepping the C reproducer for "/sys/fs/fuse/connections", it seems
> > that it tries to abort all connections.
>
> Hi Dmitry,
>
> So this could indicate a bug in the abort code of fuse, or it could
> indicate that the test case DoS-es the system so that the abort code
> simply doesn't get the resources to execute.
>
> Can the two be differentiated somehow?

I think we need to take a closer look at what happens here. I've filed
https://github.com/google/syzkaller/issues/498#issuecomment-894185550
for this.
The overall idea is that DoS should not be possible by construction
with various sandboxing so that the system does not report what is not
a bug at all. But it's not always easy to achieve.
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