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

From: syzbot
Date: Thu Apr 25 2024 - 05:06:10 EST

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Hello,

syzbot found the following issue on:

HEAD commit: 977b1ef51866 Merge tag 'block-6.9-20240420' of git://git.k..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=17080d20980000
kernel config: https://syzkaller.appspot.com/x/.config?x=f47e5e015c177e57
dashboard link: https://syzkaller.appspot.com/bug?extid=83e7f982ca045ab4405c
compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/549d1add1da9/disk-977b1ef5.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/3e8e501c8aa2/vmlinux-977b1ef5.xz
kernel image: https://storage.googleapis.com/syzbot-assets/d02f7cb905b8/bzImage-977b1ef5.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+83e7f982ca045ab4405c@xxxxxxxxxxxxxxxxxxxxxxxxx

======================================================
WARNING: possible circular locking dependency detected
6.9.0-rc4-syzkaller-00266-g977b1ef51866 #0 Not tainted
------------------------------------------------------
syz-executor.0/11241 is trying to acquire lock:
ffff888020a2c0d8 (&sighand->siglock){-.-.}-{2:2}, at: force_sig_info_to_task+0x68/0x580 kernel/signal.c:1334

but task is already holding lock:
ffff8880b943e658 (&rq->__lock){-.-.}-{2:2}, at: raw_spin_rq_lock_nested+0x2a/0x140 kernel/sched/core.c:559

which lock already depends on the new lock.

the existing dependency chain (in reverse order) is:

-> #1 (&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:1385 [inline]
_raw_spin_rq_lock_irqsave kernel/sched/sched.h:1404 [inline]
rq_lock_irqsave kernel/sched/sched.h:1683 [inline]
class_rq_lock_irqsave_constructor kernel/sched/sched.h:1737 [inline]
sched_mm_cid_exit_signals+0x17b/0x4b0 kernel/sched/core.c:12005
exit_signals+0x2a1/0x5c0 kernel/signal.c:3016
do_exit+0x6a8/0x27e0 kernel/exit.c:837
__do_sys_exit kernel/exit.c:994 [inline]
__se_sys_exit kernel/exit.c:992 [inline]
__pfx___ia32_sys_exit+0x0/0x10 kernel/exit.c:992
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
force_sig_info_to_task+0x68/0x580 kernel/signal.c:1334
force_sig_fault_to_task kernel/signal.c:1733 [inline]
force_sig_fault+0x12c/0x1d0 kernel/signal.c:1738
__bad_area_nosemaphore+0x127/0x780 arch/x86/mm/fault.c:814
handle_page_fault arch/x86/mm/fault.c:1505 [inline]
exc_page_fault+0x612/0x8e0 arch/x86/mm/fault.c:1563
asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:623
strncpy_from_user+0x2c6/0x2f0 lib/strncpy_from_user.c:138
strncpy_from_user_nofault+0x71/0x140 mm/maccess.c:186
bpf_probe_read_user_str_common kernel/trace/bpf_trace.c:216 [inline]
____bpf_probe_read_compat_str kernel/trace/bpf_trace.c:311 [inline]
bpf_probe_read_compat_str+0xe9/0x180 kernel/trace/bpf_trace.c:307
bpf_prog_e42f6260c1b72fb3+0x3d/0x3f
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+0x25a/0x490 kernel/trace/bpf_trace.c:2422
__traceiter_sched_switch+0x98/0xd0 include/trace/events/sched.h:222
trace_sched_switch include/trace/events/sched.h:222 [inline]
__schedule+0x2535/0x4a00 kernel/sched/core.c:6743
preempt_schedule_irq+0xfb/0x1c0 kernel/sched/core.c:7068
irqentry_exit+0x5e/0x90 kernel/entry/common.c:354
asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:702
force_sig_fault+0x0/0x1d0
__bad_area_nosemaphore+0x127/0x780 arch/x86/mm/fault.c:814
handle_page_fault arch/x86/mm/fault.c:1505 [inline]
exc_page_fault+0x612/0x8e0 arch/x86/mm/fault.c:1563
asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:623
__put_user_handle_exception+0x0/0x10
__do_sys_gettimeofday kernel/time/time.c:147 [inline]
__se_sys_gettimeofday+0xd9/0x240 kernel/time/time.c:140
emulate_vsyscall+0xe23/0x1290 arch/x86/entry/vsyscall/vsyscall_64.c:247
do_user_addr_fault arch/x86/mm/fault.c:1346 [inline]
handle_page_fault arch/x86/mm/fault.c:1505 [inline]
exc_page_fault+0x160/0x8e0 arch/x86/mm/fault.c:1563
asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:623
_end+0x6a9da000/0x0

other info that might help us debug this:

Possible unsafe locking scenario:

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

*** DEADLOCK ***

2 locks held by syz-executor.0/11241:
#0: ffff8880b943e658 (&rq->__lock){-.-.}-{2:2}, at: raw_spin_rq_lock_nested+0x2a/0x140 kernel/sched/core.c:559
#1: ffffffff8e334d20 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire include/linux/rcupdate.h:329 [inline]
#1: ffffffff8e334d20 (rcu_read_lock){....}-{1:2}, at: rcu_read_lock include/linux/rcupdate.h:781 [inline]
#1: ffffffff8e334d20 (rcu_read_lock){....}-{1:2}, at: __bpf_trace_run kernel/trace/bpf_trace.c:2380 [inline]
#1: ffffffff8e334d20 (rcu_read_lock){....}-{1:2}, at: bpf_trace_run4+0x16e/0x490 kernel/trace/bpf_trace.c:2422

stack backtrace:
CPU: 0 PID: 11241 Comm: syz-executor.0 Not tainted 6.9.0-rc4-syzkaller-00266-g977b1ef51866 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/27/2024
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
force_sig_info_to_task+0x68/0x580 kernel/signal.c:1334
force_sig_fault_to_task kernel/signal.c:1733 [inline]
force_sig_fault+0x12c/0x1d0 kernel/signal.c:1738
__bad_area_nosemaphore+0x127/0x780 arch/x86/mm/fault.c:814
handle_page_fault arch/x86/mm/fault.c:1505 [inline]
exc_page_fault+0x612/0x8e0 arch/x86/mm/fault.c:1563
asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:623
RIP: 0010:do_strncpy_from_user lib/strncpy_from_user.c:72 [inline]
RIP: 0010:strncpy_from_user+0x2c6/0x2f0 lib/strncpy_from_user.c:139
Code: cc cc cc cc e8 ab 95 b6 fc 45 31 ed eb e0 e8 a1 95 b6 fc 49 c7 c5 f2 ff ff ff eb d2 e8 93 95 b6 fc 49 c7 c5 f2 ff ff ff eb c4 <f3> 0f 1e fa e8 81 95 b6 fc eb a1 f3 0f 1e fa e8 76 95 b6 fc 4d 29
RSP: 0018:ffffc90009f9f5e0 EFLAGS: 00050046
RAX: 0000000000000002 RBX: ffff8880795c3584 RCX: ffff8880795c1e00
RDX: ffffc90004bf1000 RSI: 0000000000000001 RDI: 0000000000000000
RBP: 0000000000000001 R08: ffffffff84df6a34 R09: ffffffff82056cb7
R10: 0000000000000003 R11: ffff8880795c1e00 R12: 0000000000000000
R13: 0000000000000000 R14: ffffc90009f9f6a8 R15: 0000000000000000
strncpy_from_user_nofault+0x71/0x140 mm/maccess.c:186
bpf_probe_read_user_str_common kernel/trace/bpf_trace.c:216 [inline]
____bpf_probe_read_compat_str kernel/trace/bpf_trace.c:311 [inline]
bpf_probe_read_compat_str+0xe9/0x180 kernel/trace/bpf_trace.c:307
bpf_prog_e42f6260c1b72fb3+0x3d/0x3f
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+0x25a/0x490 kernel/trace/bpf_trace.c:2422
__traceiter_sched_switch+0x98/0xd0 include/trace/events/sched.h:222
trace_sched_switch include/trace/events/sched.h:222 [inline]
__schedule+0x2535/0x4a00 kernel/sched/core.c:6743
preempt_schedule_irq+0xfb/0x1c0 kernel/sched/core.c:7068
irqentry_exit+0x5e/0x90 kernel/entry/common.c:354
asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:702
RIP: 0010:force_sig_fault+0x0/0x1d0 kernel/signal.c:1737
Code: 9a 00 e9 31 ff ff ff e8 1e 7e 1a 0a 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 <f3> 0f 1e fa 55 48 89 e5 41 57 41 56 41 55 41 54 53 48 83 e4 e0 48
RSP: 0018:ffffc90009f9fb78 EFLAGS: 00000286
RAX: ffffffff8141f9d7 RBX: 0000000000000000 RCX: 0000000000040000
RDX: 0000000000000019 RSI: 0000000000000001 RDI: 000000000000000b
RBP: ffffc90009f9fc78 R08: ffffffff8141f976 R09: ffffffff81423712
R10: 0000000000000014 R11: ffff8880795c1e00 R12: dffffc0000000000
R13: ffffc90009f9fd70 R14: 1ffff920013f3fae R15: 0000000000000002
__bad_area_nosemaphore+0x127/0x780 arch/x86/mm/fault.c:814
handle_page_fault arch/x86/mm/fault.c:1505 [inline]
exc_page_fault+0x612/0x8e0 arch/x86/mm/fault.c:1563
asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:623
RIP: 0010:__put_user_handle_exception+0x0/0x10 arch/x86/lib/putuser.S:125
Code: 90 90 90 90 90 90 90 90 90 90 f3 0f 1e fa 0f 01 cb 48 89 01 31 c9 0f 01 ca c3 cc cc cc cc 66 2e 0f 1f 84 00 00 00 00 00 66 90 <0f> 01 ca b9 f2 ff ff ff c3 cc cc cc cc 0f 1f 00 90 90 90 90 90 90
RSP: 0018:ffffc90009f9fd98 EFLAGS: 00050202
RAX: 000000006624d6a7 RBX: 0000000000000000 RCX: 0000000000000019
RDX: 0000000000000000 RSI: ffffffff8bcaca20 RDI: ffffffff8c1eb160
RBP: ffffc90009f9fe50 R08: ffffffff8fa7b6af R09: 1ffffffff1f4f6d5
R10: dffffc0000000000 R11: fffffbfff1f4f6d6 R12: ffffc90009f9fde0
R13: dffffc0000000000 R14: 1ffff920013f3fb8 R15: 0000000000000019
__do_sys_gettimeofday kernel/time/time.c:147 [inline]
__se_sys_gettimeofday+0xd9/0x240 kernel/time/time.c:140
emulate_vsyscall+0xe23/0x1290 arch/x86/entry/vsyscall/vsyscall_64.c:247
do_user_addr_fault arch/x86/mm/fault.c:1346 [inline]
handle_page_fault arch/x86/mm/fault.c:1505 [inline]
exc_page_fault+0x160/0x8e0 arch/x86/mm/fault.c:1563
asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:623
RIP: 0033:_end+0x6a9da000/0x0
Code: Unable to access opcode bytes at 0xffffffffff5fffd6.
RSP: 002b:00007f9364a35b38 EFLAGS: 00010246
RAX: ffffffffffffffda RBX: 00007f9363dabf80 RCX: 00007f9363c7dea9
RDX: 00007f9364a35b40 RSI: 00007f9364a35c70 RDI: 0000000000000019
RBP: 00007f9363cca4a4 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000007 R11: 0000000000000246 R12: 0000000000000000
R13: 000000000000000b R14: 00007f9363dabf80 R15: 00007ffc4b734e88
</TASK>
----------------
Code disassembly (best guess):
0: cc int3
1: cc int3
2: cc int3
3: cc int3
4: e8 ab 95 b6 fc call 0xfcb695b4
9: 45 31 ed xor %r13d,%r13d
c: eb e0 jmp 0xffffffee
e: e8 a1 95 b6 fc call 0xfcb695b4
13: 49 c7 c5 f2 ff ff ff mov $0xfffffffffffffff2,%r13
1a: eb d2 jmp 0xffffffee
1c: e8 93 95 b6 fc call 0xfcb695b4
21: 49 c7 c5 f2 ff ff ff mov $0xfffffffffffffff2,%r13
28: eb c4 jmp 0xffffffee
* 2a: f3 0f 1e fa endbr64 <-- trapping instruction
2e: e8 81 95 b6 fc call 0xfcb695b4
33: eb a1 jmp 0xffffffd6
35: f3 0f 1e fa endbr64
39: e8 76 95 b6 fc call 0xfcb695b4
3e: 4d rex.WRB
3f: 29 .byte 0x29

---
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Next message: Vinod Koul: "Re: [PATCH] dmaengine: dmatest: fix timeout caused by kthread_stop"
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