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

From: Hillf Danton
Date: Sat Apr 27 2024 - 19:13:40 EST

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In reply to: syzbot: "Re: [syzbot] [bpf?] [trace?] possible deadlock in force_sig_info_to_task"
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On Sat, 27 Apr 2024 13:00:42 -0700
> syzbot has found a reproducer for the following issue on:
>
> HEAD commit: 5eb4573ea63d Merge tag 'soc-fixes-6.9-2' of git://git.kern..
> git tree: upstream
> console+strace: https://syzkaller.appspot.com/x/log.txt?x=17b2b240980000
> kernel config: https://syzkaller.appspot.com/x/.config?x=3d46aa9d7a44f40d
> dashboard link: https://syzkaller.appspot.com/bug?extid=83e7f982ca045ab4405c
> 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=120f79ef180000
> C reproducer: https://syzkaller.appspot.com/x/repro.c?x=13a1cd27180000
>
> Downloadable assets:
> disk image: https://storage.googleapis.com/syzbot-assets/d647177a878d/disk-5eb4573e.raw.xz
> vmlinux: https://storage.googleapis.com/syzbot-assets/977f32ca169c/vmlinux-5eb4573e.xz
> kernel image: https://storage.googleapis.com/syzbot-assets/67f3b92c1012/bzImage-5eb4573e.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-rc5-syzkaller-00296-g5eb4573ea63d #0 Not tainted
> ------------------------------------------------------
> syz-executor324/5151 is trying to acquire lock:
> ffff88802a6c8018 (&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:
>
> -> #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:1387 [inline]
> rq_lock kernel/sched/sched.h:1701 [inline]
> task_fork_fair+0x61/0x1e0 kernel/sched/fair.c:12635
> sched_cgroup_fork+0x37c/0x410 kernel/sched/core.c:4845
> copy_process+0x2217/0x3df0 kernel/fork.c:2499
> kernel_clone+0x223/0x870 kernel/fork.c:2797
> user_mode_thread+0x132/0x1a0 kernel/fork.c:2875
> rest_init+0x23/0x300 init/main.c:704
> start_kernel+0x47a/0x500 init/main.c:1081
> 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:757 [inline]
> do_exit+0x1811/0x27e0 kernel/exit.c:898
> do_group_exit+0x207/0x2c0 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+0x3f/0x40 kernel/exit.c:1036
> 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]

Given page fault with runqueue locked, bpf makes trouble instead of
helping anything in this case.

> exc_page_fault+0x612/0x8e0 arch/x86/mm/fault.c:1563
> asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:623
> rep_movs_alternative+0x22/0x70 arch/x86/lib/copy_user_64.S:48
> copy_user_generic arch/x86/include/asm/uaccess_64.h:110 [inline]
> raw_copy_from_user arch/x86/include/asm/uaccess_64.h:125 [inline]
> __copy_from_user_inatomic include/linux/uaccess.h:87 [inline]
> copy_from_user_nofault+0xbc/0x150 mm/maccess.c:125
> bpf_probe_read_user_common kernel/trace/bpf_trace.c:179 [inline]
> ____bpf_probe_read_compat kernel/trace/bpf_trace.c:292 [inline]
> bpf_probe_read_compat+0xe9/0x180 kernel/trace/bpf_trace.c:288
> bpf_prog_1878750df62aa1fb+0x48/0x4a
> 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_common+0x84/0xd0 kernel/sched/core.c:6925
> preempt_schedule+0xe1/0xf0 kernel/sched/core.c:6949
> preempt_schedule_thunk+0x1a/0x30 arch/x86/entry/thunk_64.S:12
> __raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:152 [inline]
> _raw_spin_unlock_irqrestore+0x130/0x140 kernel/locking/spinlock.c:194
> spin_unlock_irqrestore include/linux/spinlock.h:406 [inline]
> force_sig_info_to_task+0x41c/0x580 kernel/signal.c:1356
> 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
> __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:
>
> Chain exists of:
> &sighand->siglock --> &p->pi_lock --> &rq->__lock
>
> Possible unsafe locking scenario:
>
> CPU0 CPU1
> ---- ----
> lock(&rq->__lock);
> lock(&p->pi_lock);
> lock(&rq->__lock);
> lock(&sighand->siglock);
>
> *** DEADLOCK ***
>
> 2 locks held by syz-executor324/5151:
> #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: 5151 Comm: syz-executor324 Not tainted 6.9.0-rc5-syzkaller-00296-g5eb4573ea63d #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:rep_movs_alternative+0x22/0x70 arch/x86/lib/copy_user_64.S:50
> Code: 90 90 90 90 90 90 90 90 f3 0f 1e fa 48 83 f9 40 73 40 83 f9 08 73 21 85 c9 74 0f 8a 06 88 07 48 ff c7 48 ff c6 48 ff c9 75 f1 <c3> cc cc cc cc 66 0f 1f 84 00 00 00 00 00 48 8b 06 48 89 07 48 83
> RSP: 0000:ffffc90004137468 EFLAGS: 00050002
> RAX: ffffffff8205ce4e RBX: dffffc0000000000 RCX: 0000000000000002
> RDX: 0000000000000000 RSI: 0000000000000900 RDI: ffffc900041374e8
> RBP: ffff88802d039784 R08: 0000000000000005 R09: ffffffff8205ce37
> R10: 0000000000000003 R11: ffff88802d038000 R12: 1ffff11005a072f0
> R13: 0000000000000900 R14: 0000000000000002 R15: ffffc900041374e8
> copy_user_generic arch/x86/include/asm/uaccess_64.h:110 [inline]
> raw_copy_from_user arch/x86/include/asm/uaccess_64.h:125 [inline]
> __copy_from_user_inatomic include/linux/uaccess.h:87 [inline]
> copy_from_user_nofault+0xbc/0x150 mm/maccess.c:125
> bpf_probe_read_user_common kernel/trace/bpf_trace.c:179 [inline]
> ____bpf_probe_read_compat kernel/trace/bpf_trace.c:292 [inline]
> bpf_probe_read_compat+0xe9/0x180 kernel/trace/bpf_trace.c:288
> bpf_prog_1878750df62aa1fb+0x48/0x4a
> 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_common+0x84/0xd0 kernel/sched/core.c:6925
> preempt_schedule+0xe1/0xf0 kernel/sched/core.c:6949
> preempt_schedule_thunk+0x1a/0x30 arch/x86/entry/thunk_64.S:12
> __raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:152 [inline]
> _raw_spin_unlock_irqrestore+0x130/0x140 kernel/locking/spinlock.c:194
> spin_unlock_irqrestore include/linux/spinlock.h:406 [inline]
> force_sig_info_to_task+0x41c/0x580 kernel/signal.c:1356
> 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:__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: 0000:ffffc90004137d98 EFLAGS: 00050202
> RAX: 00000000662d5943 RBX: 0000000000000000 RCX: 0000000000000019
> RDX: 0000000000000000 RSI: ffffffff8bcaca20 RDI: ffffffff8c1eaba0
> RBP: ffffc90004137e50 R08: ffffffff8fa7cd6f R09: 1ffffffff1f4f9ad
> R10: dffffc0000000000 R11: fffffbfff1f4f9ae R12: ffffc90004137de0
> R13: dffffc0000000000 R14: 1ffff92000826fb8 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:00007fbb40c81c78 EFLAGS: 00010246
> RAX: ffffffffffffffda RBX: 00007fbb40d73418 RCX: 00007fbb40ce97d9
> RDX: 00007fbb40c81c80 RSI: 00007fbb40c81db0 RDI: 0000000000000019
> RBP: 00007fbb40d73410 R08: 0000000000000000 R09: 0000000000000000
> R10: 0000000000000007 R11: 0000000000000246 R12: 00007fbb40d402b0
> R13: 77735f6465686373 R14: 66aa589070d556b8 R15: 0400000000000004
> </TASK>
> syz-executor324[5151] vsyscall fault (exploit attempt?) ip:ffffffffff600000 cs:33 sp:7fbb40c81c78 ax:ffffffffffffffda si:7fbb40c81db0 di:19
> ----------------
> Code disassembly (best guess):
> 0: 90 nop
> 1: 90 nop
> 2: 90 nop
> 3: 90 nop
> 4: 90 nop
> 5: 90 nop
> 6: 90 nop
> 7: 90 nop
> 8: f3 0f 1e fa endbr64
> c: 48 83 f9 40 cmp $0x40,%rcx
> 10: 73 40 jae 0x52
> 12: 83 f9 08 cmp $0x8,%ecx
> 15: 73 21 jae 0x38
> 17: 85 c9 test %ecx,%ecx
> 19: 74 0f je 0x2a
> 1b: 8a 06 mov (%rsi),%al
> 1d: 88 07 mov %al,(%rdi)
> 1f: 48 ff c7 inc %rdi
> 22: 48 ff c6 inc %rsi
> 25: 48 ff c9 dec %rcx
> 28: 75 f1 jne 0x1b
> * 2a: c3 ret <-- trapping instruction
> 2b: cc int3
> 2c: cc int3
> 2d: cc int3
> 2e: cc int3
> 2f: 66 0f 1f 84 00 00 00 nopw 0x0(%rax,%rax,1)
> 36: 00 00
> 38: 48 8b 06 mov (%rsi),%rax
> 3b: 48 89 07 mov %rax,(%rdi)
> 3e: 48 rex.W
> 3f: 83 .byte 0x83
>
>
> ---
> If you want syzbot to run the reproducer, reply with:
> #syz test: git://repo/address.git branch-or-commit-hash
> If you attach or paste a git patch, syzbot will apply it before testing.
>

Next message: Luis Chamberlain: "Re: [PATCH v4 05/11] mm: do not split a folio if it has minimum folio order requirement"
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In reply to: syzbot: "Re: [syzbot] [bpf?] [trace?] possible deadlock in force_sig_info_to_task"
Next in thread: Linus Torvalds: "Re: [syzbot] [bpf?] [trace?] possible deadlock in force_sig_info_to_task"
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