[syzbot] [bpf?] [trace?] possible deadlock in __send_signal_locked

From: syzbot
Date: Wed Apr 17 2024 - 05:47:47 EST

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Hello,

syzbot found the following issue on:

HEAD commit: 96fca68c4fbf Merge tag 'nfsd-6.9-3' of git://git.kernel.or..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=13967bb3180000
kernel config: https://syzkaller.appspot.com/x/.config?x=85dbe39cf8e4f599
dashboard link: https://syzkaller.appspot.com/bug?extid=6e3b6eab5bd4ed584a38
compiler: gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40

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

Downloadable assets:
disk image (non-bootable): https://storage.googleapis.com/syzbot-assets/7bc7510fe41f/non_bootable_disk-96fca68c.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/d6d7a71ca443/vmlinux-96fca68c.xz
kernel image: https://storage.googleapis.com/syzbot-assets/accb76ce6c9c/bzImage-96fca68c.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+6e3b6eab5bd4ed584a38@xxxxxxxxxxxxxxxxxxxxxxxxx

======================================================
WARNING: possible circular locking dependency detected
6.9.0-rc4-syzkaller-00031-g96fca68c4fbf #0 Not tainted
------------------------------------------------------
syz-executor.0/7699 is trying to acquire lock:
ffff88806b53d998 (&pool->lock){-.-.}-{2:2}, at: __queue_work+0x23a/0x1020 kernel/workqueue.c:2346

but task is already holding lock:
ffff888023446620 (&sighand->signalfd_wqh){....}-{2:2}, at: __wake_up_common_lock kernel/sched/wait.c:105 [inline]
ffff888023446620 (&sighand->signalfd_wqh){....}-{2:2}, at: __wake_up+0x1c/0x60 kernel/sched/wait.c:127

which lock already depends on the new lock.

the existing dependency chain (in reverse order) is:

-> #3 (&sighand->signalfd_wqh){....}-{2:2}:
__raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
_raw_spin_lock_irqsave+0x3a/0x60 kernel/locking/spinlock.c:162
__wake_up_common_lock kernel/sched/wait.c:105 [inline]
__wake_up+0x1c/0x60 kernel/sched/wait.c:127
signalfd_notify include/linux/signalfd.h:22 [inline]
__send_signal_locked+0x951/0x11c0 kernel/signal.c:1168
do_notify_parent+0xeb4/0x1040 kernel/signal.c:2143
exit_notify kernel/exit.c:754 [inline]
do_exit+0x1369/0x2c10 kernel/exit.c:898
do_group_exit+0xd3/0x2a0 kernel/exit.c:1027
__do_sys_exit_group kernel/exit.c:1038 [inline]
__se_sys_exit_group kernel/exit.c:1036 [inline]
__x64_sys_exit_group+0x3e/0x50 kernel/exit.c:1036
do_syscall_x64 arch/x86/entry/common.c:52 [inline]
do_syscall_64+0xcf/0x260 arch/x86/entry/common.c:83
entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #2 (&sighand->siglock){-...}-{2:2}:
__raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
_raw_spin_lock_irqsave+0x3a/0x60 kernel/locking/spinlock.c:162
__lock_task_sighand+0xc2/0x340 kernel/signal.c:1414
lock_task_sighand include/linux/sched/signal.h:746 [inline]
do_send_sig_info kernel/signal.c:1300 [inline]
group_send_sig_info+0x290/0x300 kernel/signal.c:1453
bpf_send_signal_common+0x2e8/0x3a0 kernel/trace/bpf_trace.c:881
____bpf_send_signal_thread kernel/trace/bpf_trace.c:898 [inline]
bpf_send_signal_thread+0x16/0x20 kernel/trace/bpf_trace.c:896
___bpf_prog_run+0x3e51/0xabd0 kernel/bpf/core.c:1997
__bpf_prog_run32+0xc1/0x100 kernel/bpf/core.c:2236
bpf_dispatcher_nop_func include/linux/bpf.h:1234 [inline]
__bpf_prog_run include/linux/filter.h:657 [inline]
bpf_prog_run include/linux/filter.h:664 [inline]
__bpf_trace_run kernel/trace/bpf_trace.c:2381 [inline]
bpf_trace_run4+0x176/0x460 kernel/trace/bpf_trace.c:2422
__bpf_trace_mmap_lock_acquire_returned+0x134/0x180 include/trace/events/mmap_lock.h:52
trace_mmap_lock_acquire_returned include/trace/events/mmap_lock.h:52 [inline]
__mmap_lock_do_trace_acquire_returned+0x456/0x790 mm/mmap_lock.c:237
__mmap_lock_trace_acquire_returned include/linux/mmap_lock.h:36 [inline]
mmap_write_lock include/linux/mmap_lock.h:109 [inline]
__do_sys_set_mempolicy_home_node+0x574/0x860 mm/mempolicy.c:1568
do_syscall_x64 arch/x86/entry/common.c:52 [inline]
do_syscall_64+0xcf/0x260 arch/x86/entry/common.c:83
entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #1 (lock#11){+.+.}-{2:2}:
local_lock_acquire include/linux/local_lock_internal.h:29 [inline]
__mmap_lock_do_trace_acquire_returned+0x97/0x790 mm/mmap_lock.c:237
__mmap_lock_trace_acquire_returned include/linux/mmap_lock.h:36 [inline]
mmap_read_trylock include/linux/mmap_lock.h:166 [inline]
stack_map_get_build_id_offset+0x5df/0x7d0 kernel/bpf/stackmap.c:141
__bpf_get_stack+0x6bf/0x700 kernel/bpf/stackmap.c:449
____bpf_get_stack_raw_tp kernel/trace/bpf_trace.c:1985 [inline]
bpf_get_stack_raw_tp+0x124/0x160 kernel/trace/bpf_trace.c:1975
___bpf_prog_run+0x3e51/0xabd0 kernel/bpf/core.c:1997
__bpf_prog_run32+0xc1/0x100 kernel/bpf/core.c:2236
bpf_dispatcher_nop_func include/linux/bpf.h:1234 [inline]
__bpf_prog_run include/linux/filter.h:657 [inline]
bpf_prog_run include/linux/filter.h:664 [inline]
__bpf_trace_run kernel/trace/bpf_trace.c:2381 [inline]
bpf_trace_run3+0x167/0x440 kernel/trace/bpf_trace.c:2421
__bpf_trace_workqueue_queue_work+0x101/0x140 include/trace/events/workqueue.h:23
trace_workqueue_queue_work include/trace/events/workqueue.h:23 [inline]
__queue_work+0x627/0x1020 kernel/workqueue.c:2382
queue_work_on+0xf4/0x120 kernel/workqueue.c:2435
bpf_prog_load+0x19bb/0x2660 kernel/bpf/syscall.c:2944
__sys_bpf+0x9b4/0x4b40 kernel/bpf/syscall.c:5660
__do_sys_bpf kernel/bpf/syscall.c:5767 [inline]
__se_sys_bpf kernel/bpf/syscall.c:5765 [inline]
__x64_sys_bpf+0x78/0xc0 kernel/bpf/syscall.c:5765
do_syscall_x64 arch/x86/entry/common.c:52 [inline]
do_syscall_64+0xcf/0x260 arch/x86/entry/common.c:83
entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #0 (&pool->lock){-.-.}-{2:2}:
check_prev_add kernel/locking/lockdep.c:3134 [inline]
check_prevs_add kernel/locking/lockdep.c:3253 [inline]
validate_chain kernel/locking/lockdep.c:3869 [inline]
__lock_acquire+0x2478/0x3b30 kernel/locking/lockdep.c:5137
lock_acquire kernel/locking/lockdep.c:5754 [inline]
lock_acquire+0x1b1/0x560 kernel/locking/lockdep.c:5719
__raw_spin_lock include/linux/spinlock_api_smp.h:133 [inline]
_raw_spin_lock+0x2e/0x40 kernel/locking/spinlock.c:154
__queue_work+0x23a/0x1020 kernel/workqueue.c:2346
queue_work_on+0xf4/0x120 kernel/workqueue.c:2435
queue_work include/linux/workqueue.h:605 [inline]
schedule_work include/linux/workqueue.h:666 [inline]
p9_pollwake+0xc1/0x1d0 net/9p/trans_fd.c:538
__wake_up_common+0x131/0x1e0 kernel/sched/wait.c:89
__wake_up_common_lock kernel/sched/wait.c:106 [inline]
__wake_up+0x31/0x60 kernel/sched/wait.c:127
signalfd_notify include/linux/signalfd.h:22 [inline]
__send_signal_locked+0x951/0x11c0 kernel/signal.c:1168
force_sig_info_to_task+0x31d/0x660 kernel/signal.c:1352
force_sig_fault_to_task kernel/signal.c:1733 [inline]
force_sig_fault+0xc5/0x110 kernel/signal.c:1738
__bad_area_nosemaphore+0x30d/0x6b0 arch/x86/mm/fault.c:854
bad_area_access_error+0xc1/0x260 arch/x86/mm/fault.c:931
do_user_addr_fault+0xa2a/0x1080 arch/x86/mm/fault.c:1396
handle_page_fault arch/x86/mm/fault.c:1505 [inline]
exc_page_fault+0x5c/0xc0 arch/x86/mm/fault.c:1563
asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:623

other info that might help us debug this:

Chain exists of:
&pool->lock --> &sighand->siglock --> &sighand->signalfd_wqh

Possible unsafe locking scenario:

CPU0 CPU1
---- ----
lock(&sighand->signalfd_wqh);
lock(&sighand->siglock);
lock(&sighand->signalfd_wqh);
lock(&pool->lock);

*** DEADLOCK ***

3 locks held by syz-executor.0/7699:
#0: ffff8880234465d8 (&sighand->siglock){-...}-{2:2}, at: force_sig_info_to_task+0x7a/0x660 kernel/signal.c:1334
#1: ffff888023446620 (&sighand->signalfd_wqh){....}-{2:2}, at: __wake_up_common_lock kernel/sched/wait.c:105 [inline]
#1: ffff888023446620 (&sighand->signalfd_wqh){....}-{2:2}, at: __wake_up+0x1c/0x60 kernel/sched/wait.c:127
#2: ffffffff8d7b0e20 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire include/linux/rcupdate.h:329 [inline]
#2: ffffffff8d7b0e20 (rcu_read_lock){....}-{1:2}, at: rcu_read_lock include/linux/rcupdate.h:781 [inline]
#2: ffffffff8d7b0e20 (rcu_read_lock){....}-{1:2}, at: __queue_work+0xf2/0x1020 kernel/workqueue.c:2324

stack backtrace:
CPU: 2 PID: 7699 Comm: syz-executor.0 Not tainted 6.9.0-rc4-syzkaller-00031-g96fca68c4fbf #0
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.2-debian-1.16.2-1 04/01/2014
Call Trace:
<TASK>
__dump_stack lib/dump_stack.c:88 [inline]
dump_stack_lvl+0x116/0x1f0 lib/dump_stack.c:114
check_noncircular+0x31a/0x400 kernel/locking/lockdep.c:2187
check_prev_add kernel/locking/lockdep.c:3134 [inline]
check_prevs_add kernel/locking/lockdep.c:3253 [inline]
validate_chain kernel/locking/lockdep.c:3869 [inline]
__lock_acquire+0x2478/0x3b30 kernel/locking/lockdep.c:5137
lock_acquire kernel/locking/lockdep.c:5754 [inline]
lock_acquire+0x1b1/0x560 kernel/locking/lockdep.c:5719
__raw_spin_lock include/linux/spinlock_api_smp.h:133 [inline]
_raw_spin_lock+0x2e/0x40 kernel/locking/spinlock.c:154
__queue_work+0x23a/0x1020 kernel/workqueue.c:2346
queue_work_on+0xf4/0x120 kernel/workqueue.c:2435
queue_work include/linux/workqueue.h:605 [inline]
schedule_work include/linux/workqueue.h:666 [inline]
p9_pollwake+0xc1/0x1d0 net/9p/trans_fd.c:538
__wake_up_common+0x131/0x1e0 kernel/sched/wait.c:89
__wake_up_common_lock kernel/sched/wait.c:106 [inline]
__wake_up+0x31/0x60 kernel/sched/wait.c:127
signalfd_notify include/linux/signalfd.h:22 [inline]
__send_signal_locked+0x951/0x11c0 kernel/signal.c:1168
force_sig_info_to_task+0x31d/0x660 kernel/signal.c:1352
force_sig_fault_to_task kernel/signal.c:1733 [inline]
force_sig_fault+0xc5/0x110 kernel/signal.c:1738
__bad_area_nosemaphore+0x30d/0x6b0 arch/x86/mm/fault.c:854
bad_area_access_error+0xc1/0x260 arch/x86/mm/fault.c:931
do_user_addr_fault+0xa2a/0x1080 arch/x86/mm/fault.c:1396
handle_page_fault arch/x86/mm/fault.c:1505 [inline]
exc_page_fault+0x5c/0xc0 arch/x86/mm/fault.c:1563
asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:623
RIP: 0033:0x7f809a860675
Code: fe 28 6f 06 48 83 fa 40 0f 87 a7 00 00 00 62 e1 fe 28 6f 4c 16 ff 62 e1 fe 28 7f 07 62 e1 fe 28 7f 4c 17 ff c3 8b 0e 8b 34 16 <89> 0f 89 34 17 c3 0f 1f 44 00 00 83 fa 10 73 21 83 fa 08 73 36 48
RSP: 002b:00007fff068363a8 EFLAGS: 00010202
RAX: 0000000020000080 RBX: 0000000000000004 RCX: 0000000034747865
RDX: 0000000000000001 RSI: 0000000000347478 RDI: 0000000020000080
RBP: 00007f809a9ad980 R08: 00007f809a800000 R09: 0000000000000001
R10: 0000000000000001 R11: 0000000000000009 R12: 0000000000018980
R13: 000000000001894e R14: 00007fff06836550 R15: 00007f809a834cb0
</TASK>

---
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