[syzbot] [bpf?] possible deadlock in __lock_task_sighand (3)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 30a92c9e3d6b openvswitch: Set the skbuff pkt_type for prop..
git tree: net
console+strace: https://syzkaller.appspot.com/x/log.txt?x=166c4e42980000
kernel config: https://syzkaller.appspot.com/x/.config?x=17ffd15f654c98ba
dashboard link: https://syzkaller.appspot.com/bug?extid=f2ed7d5888894fedf676
compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=16c203f0980000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=12046634980000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/613ea2adf735/disk-30a92c9e.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/2d370db074ef/vmlinux-30a92c9e.xz
kernel image: https://storage.googleapis.com/syzbot-assets/7e9ed7a24991/bzImage-30a92c9e.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+f2ed7d...@syzkaller.appspotmail.com

======================================================
WARNING: possible circular locking dependency detected
6.9.0-syzkaller-08557-g30a92c9e3d6b #0 Not tainted
------------------------------------------------------
strace-static-x/5086 is trying to acquire lock:
ffff8880183f9bd8 (&sighand->siglock){-...}-{2:2}, at: __lock_task_sighand+0x149/0x2d0 kernel/signal.c:1414

but task is already holding lock:
ffff8880b9538828 (lock#9){+.+.}-{2:2}, at: local_lock_acquire include/linux/local_lock_internal.h:29 [inline]
ffff8880b9538828 (lock#9){+.+.}-{2:2}, at: __mmap_lock_do_trace_acquire_returned+0x8f/0x630 mm/mmap_lock.c:237

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #3 (lock#9){+.+.}-{2:2}:
lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5754
local_lock_acquire include/linux/local_lock_internal.h:29 [inline]
__mmap_lock_do_trace_acquire_returned+0xa8/0x630 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+0x9b2/0x9d0 kernel/bpf/stackmap.c:141
__bpf_get_stack+0x4ad/0x5a0 kernel/bpf/stackmap.c:449
____bpf_get_stack_raw_tp kernel/trace/bpf_trace.c:1994 [inline]
bpf_get_stack_raw_tp+0x1a3/0x240 kernel/trace/bpf_trace.c:1984
bpf_prog_ec3b2eefa702d8d3+0x42/0x46
bpf_dispatcher_nop_func include/linux/bpf.h:1243 [inline]
__bpf_prog_run include/linux/filter.h:691 [inline]
bpf_prog_run include/linux/filter.h:698 [inline]
__bpf_trace_run kernel/trace/bpf_trace.c:2403 [inline]
bpf_trace_run2+0x2ec/0x540 kernel/trace/bpf_trace.c:2444
__traceiter_tlb_flush+0x77/0xd0 include/trace/events/tlb.h:38
trace_tlb_flush+0x118/0x140 include/trace/events/tlb.h:38
switch_mm_irqs_off+0x7cb/0xae0
context_switch kernel/sched/core.c:5392 [inline]
__schedule+0x1066/0x4a50 kernel/sched/core.c:6745
preempt_schedule_common+0x84/0xd0 kernel/sched/core.c:6924
preempt_schedule+0xe1/0xf0 kernel/sched/core.c:6948
preempt_schedule_thunk+0x1a/0x30 arch/x86/entry/thunk.S:12
__raw_spin_unlock include/linux/spinlock_api_smp.h:143 [inline]
_raw_spin_unlock+0x3e/0x50 kernel/locking/spinlock.c:186
spin_unlock include/linux/spinlock.h:391 [inline]
__text_poke+0xa6b/0xd30 arch/x86/kernel/alternative.c:1944
text_poke arch/x86/kernel/alternative.c:1968 [inline]
text_poke_bp_batch+0x265/0xb30 arch/x86/kernel/alternative.c:2276
text_poke_flush arch/x86/kernel/alternative.c:2470 [inline]
text_poke_finish+0x30/0x50 arch/x86/kernel/alternative.c:2477
arch_jump_label_transform_apply+0x1c/0x30 arch/x86/kernel/jump_label.c:146
static_key_enable_cpuslocked+0x136/0x260 kernel/jump_label.c:205
static_key_enable+0x1a/0x20 kernel/jump_label.c:218
tracepoint_add_func+0x953/0x9e0 kernel/tracepoint.c:361
tracepoint_probe_register_prio_may_exist+0x122/0x190 kernel/tracepoint.c:482
bpf_raw_tp_link_attach+0x48b/0x6e0 kernel/bpf/syscall.c:3874
bpf_raw_tracepoint_open+0x1c2/0x240 kernel/bpf/syscall.c:3905
__sys_bpf+0x3c0/0x810 kernel/bpf/syscall.c:5729
__do_sys_bpf kernel/bpf/syscall.c:5794 [inline]
__se_sys_bpf kernel/bpf/syscall.c:5792 [inline]
__x64_sys_bpf+0x7c/0x90 kernel/bpf/syscall.c:5792
do_syscall_x64 arch/x86/entry/common.c:52 [inline]
do_syscall_64+0xf5/0x240 arch/x86/entry/common.c:83
entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #2 (&rq->__lock){-.-.}-{2:2}:
lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5754
_raw_spin_lock_nested+0x31/0x40 kernel/locking/spinlock.c:378
raw_spin_rq_lock_nested+0x2a/0x140 kernel/sched/core.c:559
raw_spin_rq_lock kernel/sched/sched.h:1406 [inline]
rq_lock kernel/sched/sched.h:1702 [inline]
task_fork_fair+0x61/0x1e0 kernel/sched/fair.c:12709
sched_cgroup_fork+0x37c/0x410 kernel/sched/core.c:4844
copy_process+0x2217/0x3dc0 kernel/fork.c:2499
kernel_clone+0x226/0x8f0 kernel/fork.c:2797
user_mode_thread+0x132/0x1a0 kernel/fork.c:2875
rest_init+0x23/0x300 init/main.c:707
start_kernel+0x47a/0x500 init/main.c:1084
x86_64_start_reservations+0x2a/0x30 arch/x86/kernel/head64.c:507
x86_64_start_kernel+0x99/0xa0 arch/x86/kernel/head64.c:488
common_startup_64+0x13e/0x147

-> #1 (&p->pi_lock){-.-.}-{2:2}:
lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5754
__raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
_raw_spin_lock_irqsave+0xd5/0x120 kernel/locking/spinlock.c:162
class_raw_spinlock_irqsave_constructor include/linux/spinlock.h:553 [inline]
try_to_wake_up+0xb0/0x1470 kernel/sched/core.c:4262
signal_wake_up_state+0xb4/0x120 kernel/signal.c:773
signal_wake_up include/linux/sched/signal.h:448 [inline]
complete_signal+0x94a/0xcf0 kernel/signal.c:1065
__send_signal_locked+0xb1b/0xdc0 kernel/signal.c:1185
do_notify_parent+0xd96/0x10a0 kernel/signal.c:2143
exit_notify kernel/exit.c:756 [inline]
do_exit+0x1811/0x27e0 kernel/exit.c:897
do_group_exit+0x207/0x2c0 kernel/exit.c:1026
__do_sys_exit_group kernel/exit.c:1037 [inline]
__se_sys_exit_group kernel/exit.c:1035 [inline]
__x64_sys_exit_group+0x3f/0x40 kernel/exit.c:1035
do_syscall_x64 arch/x86/entry/common.c:52 [inline]
do_syscall_64+0xf5/0x240 arch/x86/entry/common.c:83
entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #0 (&sighand->siglock){-...}-{2:2}:
check_prev_add kernel/locking/lockdep.c:3134 [inline]
check_prevs_add kernel/locking/lockdep.c:3253 [inline]
validate_chain+0x18cb/0x58e0 kernel/locking/lockdep.c:3869
__lock_acquire+0x1346/0x1fd0 kernel/locking/lockdep.c:5137
lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5754
__raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
_raw_spin_lock_irqsave+0xd5/0x120 kernel/locking/spinlock.c:162
__lock_task_sighand+0x149/0x2d0 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+0x274/0x310 kernel/signal.c:1453
bpf_send_signal_common+0x2dd/0x430 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_16ecb682114cf56a+0x22/0x2a
bpf_dispatcher_nop_func include/linux/bpf.h:1243 [inline]
__bpf_prog_run include/linux/filter.h:691 [inline]
bpf_prog_run include/linux/filter.h:698 [inline]
__bpf_trace_run kernel/trace/bpf_trace.c:2403 [inline]
bpf_trace_run4+0x334/0x590 kernel/trace/bpf_trace.c:2446
__traceiter_mmap_lock_acquire_returned+0x93/0xf0 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+0x5c8/0x630 mm/mmap_lock.c:237
__mmap_lock_trace_acquire_returned include/linux/mmap_lock.h:36 [inline]
mmap_read_lock include/linux/mmap_lock.h:147 [inline]
process_vm_rw_single_vec mm/process_vm_access.c:105 [inline]
process_vm_rw_core mm/process_vm_access.c:216 [inline]
process_vm_rw+0xa46/0xcf0 mm/process_vm_access.c:284
__do_sys_process_vm_readv mm/process_vm_access.c:296 [inline]
__se_sys_process_vm_readv mm/process_vm_access.c:292 [inline]
__x64_sys_process_vm_readv+0xe0/0x100 mm/process_vm_access.c:292
do_syscall_x64 arch/x86/entry/common.c:52 [inline]
do_syscall_64+0xf5/0x240 arch/x86/entry/common.c:83
entry_SYSCALL_64_after_hwframe+0x77/0x7f

other info that might help us debug this:

Chain exists of:
&sighand->siglock --> &rq->__lock --> lock#9

Possible unsafe locking scenario:

CPU0 CPU1
---- ----
lock(lock#9);
lock(&rq->__lock);
lock(lock#9);
lock(&sighand->siglock);

*** DEADLOCK ***

5 locks held by strace-static-x/5086:
#0: ffff88802f77cda0 (&mm->mmap_lock){++++}-{3:3}, at: mmap_read_lock include/linux/mmap_lock.h:146 [inline]
#0: ffff88802f77cda0 (&mm->mmap_lock){++++}-{3:3}, at: process_vm_rw_single_vec mm/process_vm_access.c:105 [inline]
#0: ffff88802f77cda0 (&mm->mmap_lock){++++}-{3:3}, at: process_vm_rw_core mm/process_vm_access.c:216 [inline]
#0: ffff88802f77cda0 (&mm->mmap_lock){++++}-{3:3}, at: process_vm_rw+0x6e9/0xcf0 mm/process_vm_access.c:284
#1: ffff8880b9538828 (lock#9){+.+.}-{2:2}, at: local_lock_acquire include/linux/local_lock_internal.h:29 [inline]
#1: ffff8880b9538828 (lock#9){+.+.}-{2:2}, at: __mmap_lock_do_trace_acquire_returned+0x8f/0x630 mm/mmap_lock.c:237
#2: ffffffff8e333d20 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire include/linux/rcupdate.h:329 [inline]
#2: ffffffff8e333d20 (rcu_read_lock){....}-{1:2}, at: rcu_read_lock include/linux/rcupdate.h:781 [inline]
#2: ffffffff8e333d20 (rcu_read_lock){....}-{1:2}, at: get_memcg_path_buf mm/mmap_lock.c:139 [inline]
#2: ffffffff8e333d20 (rcu_read_lock){....}-{1:2}, at: get_mm_memcg_path+0xb1/0x600 mm/mmap_lock.c:209
#3: ffffffff8e333d20 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire include/linux/rcupdate.h:329 [inline]
#3: ffffffff8e333d20 (rcu_read_lock){....}-{1:2}, at: rcu_read_lock include/linux/rcupdate.h:781 [inline]
#3: ffffffff8e333d20 (rcu_read_lock){....}-{1:2}, at: __bpf_trace_run kernel/trace/bpf_trace.c:2402 [inline]
#3: ffffffff8e333d20 (rcu_read_lock){....}-{1:2}, at: bpf_trace_run4+0x244/0x590 kernel/trace/bpf_trace.c:2446
#4: ffffffff8e333d20 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire include/linux/rcupdate.h:329 [inline]
#4: ffffffff8e333d20 (rcu_read_lock){....}-{1:2}, at: rcu_read_lock include/linux/rcupdate.h:781 [inline]
#4: ffffffff8e333d20 (rcu_read_lock){....}-{1:2}, at: __lock_task_sighand+0x29/0x2d0 kernel/signal.c:1397

stack backtrace:
CPU: 1 PID: 5086 Comm: strace-static-x Not tainted 6.9.0-syzkaller-08557-g30a92c9e3d6b #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/02/2024
Call Trace:
<TASK>
__dump_stack lib/dump_stack.c:88 [inline]
dump_stack_lvl+0x241/0x360 lib/dump_stack.c:114
check_noncircular+0x36a/0x4a0 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+0x18cb/0x58e0 kernel/locking/lockdep.c:3869
__lock_acquire+0x1346/0x1fd0 kernel/locking/lockdep.c:5137
lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5754
__raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
_raw_spin_lock_irqsave+0xd5/0x120 kernel/locking/spinlock.c:162
__lock_task_sighand+0x149/0x2d0 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+0x274/0x310 kernel/signal.c:1453
bpf_send_signal_common+0x2dd/0x430 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_16ecb682114cf56a+0x22/0x2a
bpf_dispatcher_nop_func include/linux/bpf.h:1243 [inline]
__bpf_prog_run include/linux/filter.h:691 [inline]
bpf_prog_run include/linux/filter.h:698 [inline]
__bpf_trace_run kernel/trace/bpf_trace.c:2403 [inline]
bpf_trace_run4+0x334/0x590 kernel/trace/bpf_trace.c:2446
__traceiter_mmap_lock_acquire_returned+0x93/0xf0 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+0x5c8/0x630 mm/mmap_lock.c:237
__mmap_lock_trace_acquire_returned include/linux/mmap_lock.h:36 [inline]
mmap_read_lock include/linux/mmap_lock.h:147 [inline]
process_vm_rw_single_vec mm/process_vm_access.c:105 [inline]
process_vm_rw_core mm/process_vm_access.c:216 [inline]
process_vm_rw+0xa46/0xcf0 mm/process_vm_access.c:284
__do_sys_process_vm_readv mm/process_vm_access.c:296 [inline]
__se_sys_process_vm_readv mm/process_vm_access.c:292 [inline]
__x64_sys_process_vm_readv+0xe0/0x100 mm/process_vm_access.c:292
do_syscall_x64 arch/x86/entry/common.c:52 [inline]
do_syscall_64+0xf5/0x240 arch/x86/entry/common.c:83
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x4eacda
Code: 48 c7 c2 a8 ff ff ff f7 d8 64 89 02 b8 ff ff ff ff eb d2 e8 38 12 00 00 0f 1f 84 00 00 00 00 00 49 89 ca b8 36 01 00 00 0f 05 <48> 3d 00 f0 ff ff 77 06 c3 0f 1f 44 00 00 48 c7 c2 a8 ff ff ff f7
RSP: 002b:00007ffe656d7be8 EFLAGS: 00000246 ORIG_RAX: 0000000000000136
RAX: ffffffffffffffda RBX: 0000000020000000 RCX: 00000000004eacda
RDX: 0000000000000001 RSI: 00007ffe656d7c10 RDI: 00000000000013eb
RBP: 0000000000000000 R08: 0000000000000001 R09: 0000000000000000
R10: 00007ffe656d7c20 R11: 0000000000000246 R12: 0000000020000080
R13: 0000000012d21a30 R14: 0000000000001000 R15: 0000000000000010
</TASK>


---
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[syzbot]

syzbot has bisected this issue to:

commit fbd94c7afcf99c9f3b1ba1168657ecc428eb2c8d
Author: Alexei Starovoitov <a...@kernel.org>
Date: Wed Dec 1 18:10:28 2021 +0000

bpf: Pass a set of bpf_core_relo-s to prog_load command.

bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=149b9a2c980000
start commit: 30a92c9e3d6b openvswitch: Set the skbuff pkt_type for prop..
git tree: net
final oops: https://syzkaller.appspot.com/x/report.txt?x=169b9a2c980000
console output: https://syzkaller.appspot.com/x/log.txt?x=129b9a2c980000

kernel config: https://syzkaller.appspot.com/x/.config?x=17ffd15f654c98ba
dashboard link: https://syzkaller.appspot.com/bug?extid=f2ed7d5888894fedf676

syz repro: https://syzkaller.appspot.com/x/repro.syz?x=16c203f0980000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=12046634980000

Reported-by: syzbot+f2ed7d...@syzkaller.appspotmail.com
Fixes: fbd94c7afcf9 ("bpf: Pass a set of bpf_core_relo-s to prog_load command.")

For information about bisection process see: https://goo.gl/tpsmEJ#bisection