Message-ID: <CAADnVQJVJADKw0KC6GzhSOjA8DJFammARKwVh+TeNAD7U3h91A@mail.gmail.com>
Date: Fri, 6 Dec 2024 10:59:20 -0800
From: Alexei Starovoitov <alexei.starovoitov@...il.com>
To: syzbot <syzbot+0a26db48dcd6d80be6c0@...kaller.appspotmail.com>, 
	Kumar Kartikeya Dwivedi <memxor@...il.com>
Cc: Andrii Nakryiko <andrii@...nel.org>, Alexei Starovoitov <ast@...nel.org>, bpf <bpf@...r.kernel.org>, 
	Daniel Borkmann <daniel@...earbox.net>, Eddy Z <eddyz87@...il.com>, Hao Luo <haoluo@...gle.com>, 
	John Fastabend <john.fastabend@...il.com>, Jiri Olsa <jolsa@...nel.org>, 
	KP Singh <kpsingh@...nel.org>, LKML <linux-kernel@...r.kernel.org>, 
	Martin KaFai Lau <martin.lau@...ux.dev>, Stanislav Fomichev <sdf@...ichev.me>, Song Liu <song@...nel.org>, 
	syzkaller-bugs <syzkaller-bugs@...glegroups.com>, Yonghong Song <yonghong.song@...ux.dev>
Subject: Re: [syzbot] [bpf?] possible deadlock in htab_lru_map_delete_elem

Kumar,

check out this ABBA deadlock that your upcoming resilient
spin lock should address.
There are two hash maps and though we have htab->map_locked
recursion protection it doesn't help here.

On Fri, Dec 6, 2024 at 5:58 AM syzbot
<syzbot+0a26db48dcd6d80be6c0@...kaller.appspotmail.com> wrote:
>
> Hello,
>
> syzbot found the following issue on:
>
> HEAD commit:    feffde684ac2 Merge tag 'for-6.13-rc1-tag' of git://git.ker..
> git tree:       upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=1476e0f8580000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=6851fe4f61792030
> dashboard link: https://syzkaller.appspot.com/bug?extid=0a26db48dcd6d80be6c0
> compiler:       gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=17d9c8df980000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=1276e0f8580000
>
> Downloadable assets:
> disk image (non-bootable): https://storage.googleapis.com/syzbot-assets/7feb34a89c2a/non_bootable_disk-feffde68.raw.xz
> vmlinux: https://storage.googleapis.com/syzbot-assets/e9751e7030ea/vmlinux-feffde68.xz
> kernel image: https://storage.googleapis.com/syzbot-assets/f7bf928b44d6/bzImage-feffde68.xz
>
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+0a26db48dcd6d80be6c0@...kaller.appspotmail.com
>
> ======================================================
> WARNING: possible circular locking dependency detected
> 6.13.0-rc1-syzkaller-00025-gfeffde684ac2 #0 Not tainted
> ------------------------------------------------------
> syz-executor207/6807 is trying to acquire lock:
> ffff88802632eca0 (&htab->lockdep_key#434){....}-{2:2}, at: htab_lock_bucket kernel/bpf/hashtab.c:167 [inline]
> ffff88802632eca0 (&htab->lockdep_key#434){....}-{2:2}, at: htab_lru_map_delete_elem+0x1c8/0x790 kernel/bpf/hashtab.c:1484
>
> but task is already holding lock:
> ffff888031440e20 (&htab->lockdep_key#435){....}-{2:2}, at: htab_lock_bucket kernel/bpf/hashtab.c:167 [inline]
> ffff888031440e20 (&htab->lockdep_key#435){....}-{2:2}, at: htab_lru_map_delete_elem+0x1c8/0x790 kernel/bpf/hashtab.c:1484
>
> which lock already depends on the new lock.
>
>
> the existing dependency chain (in reverse order) is:
>
> -> #1 (&htab->lockdep_key#435){....}-{2:2}:
>        __raw_spin_lock include/linux/spinlock_api_smp.h:133 [inline]
>        _raw_spin_lock+0x2e/0x40 kernel/locking/spinlock.c:154
>        htab_lock_bucket kernel/bpf/hashtab.c:167 [inline]
>        htab_lru_map_delete_elem+0x1c8/0x790 kernel/bpf/hashtab.c:1484
>        bpf_prog_2c29ac5cdc6b1842+0x43/0x47
>        bpf_dispatcher_nop_func include/linux/bpf.h:1290 [inline]
>        __bpf_prog_run include/linux/filter.h:701 [inline]
>        bpf_prog_run include/linux/filter.h:708 [inline]
>        __bpf_trace_run kernel/trace/bpf_trace.c:2351 [inline]
>        bpf_trace_run2+0x231/0x590 kernel/trace/bpf_trace.c:2392
>        __bpf_trace_contention_begin+0xca/0x110 include/trace/events/lock.h:95
>        __traceiter_contention_begin+0x5a/0xa0 include/trace/events/lock.h:95
>        __preempt_count_dec_and_test arch/x86/include/asm/preempt.h:94 [inline]
>        class_preempt_notrace_destructor include/linux/preempt.h:481 [inline]
>        trace_contention_begin.constprop.0+0xf3/0x170 include/trace/events/lock.h:95
>        __pv_queued_spin_lock_slowpath+0x10b/0xc90 kernel/locking/qspinlock.c:402
>        pv_queued_spin_lock_slowpath arch/x86/include/asm/paravirt.h:584 [inline]
>        queued_spin_lock_slowpath arch/x86/include/asm/qspinlock.h:51 [inline]
>        queued_spin_lock include/asm-generic/qspinlock.h:114 [inline]
>        do_raw_spin_lock+0x210/0x2c0 kernel/locking/spinlock_debug.c:116
>        htab_lock_bucket kernel/bpf/hashtab.c:167 [inline]
>        htab_lru_map_delete_elem+0x1c8/0x790 kernel/bpf/hashtab.c:1484
>        bpf_prog_2c29ac5cdc6b1842+0x43/0x47
>        bpf_dispatcher_nop_func include/linux/bpf.h:1290 [inline]
>        __bpf_prog_run include/linux/filter.h:701 [inline]
>        bpf_prog_run include/linux/filter.h:708 [inline]
>        __bpf_trace_run kernel/trace/bpf_trace.c:2351 [inline]
>        bpf_trace_run2+0x231/0x590 kernel/trace/bpf_trace.c:2392
>        __bpf_trace_contention_begin+0xca/0x110 include/trace/events/lock.h:95
>        __traceiter_contention_begin+0x5a/0xa0 include/trace/events/lock.h:95
>        trace_contention_begin+0xd2/0x140 include/trace/events/lock.h:95
>        __mutex_lock_common kernel/locking/mutex.c:587 [inline]
>        __mutex_lock+0x1a8/0xa60 kernel/locking/mutex.c:735
>        futex_cleanup_begin kernel/futex/core.c:1070 [inline]
>        futex_exit_release+0x2a/0x220 kernel/futex/core.c:1122
>        exit_mm_release+0x19/0x30 kernel/fork.c:1660
>        exit_mm kernel/exit.c:543 [inline]
>        do_exit+0x88b/0x2d70 kernel/exit.c:925
>        do_group_exit+0xd3/0x2a0 kernel/exit.c:1087
>        __do_sys_exit_group kernel/exit.c:1098 [inline]
>        __se_sys_exit_group kernel/exit.c:1096 [inline]
>        __x64_sys_exit_group+0x3e/0x50 kernel/exit.c:1096
>        x64_sys_call+0x151f/0x1720 arch/x86/include/generated/asm/syscalls_64.h:232
>        do_syscall_x64 arch/x86/entry/common.c:52 [inline]
>        do_syscall_64+0xcd/0x250 arch/x86/entry/common.c:83
>        entry_SYSCALL_64_after_hwframe+0x77/0x7f
>
> -> #0 (&htab->lockdep_key#434){....}-{2:2}:
>        check_prev_add kernel/locking/lockdep.c:3161 [inline]
>        check_prevs_add kernel/locking/lockdep.c:3280 [inline]
>        validate_chain kernel/locking/lockdep.c:3904 [inline]
>        __lock_acquire+0x249e/0x3c40 kernel/locking/lockdep.c:5226
>        lock_acquire.part.0+0x11b/0x380 kernel/locking/lockdep.c:5849
>        __raw_spin_lock include/linux/spinlock_api_smp.h:133 [inline]
>        _raw_spin_lock+0x2e/0x40 kernel/locking/spinlock.c:154
>        htab_lock_bucket kernel/bpf/hashtab.c:167 [inline]
>        htab_lru_map_delete_elem+0x1c8/0x790 kernel/bpf/hashtab.c:1484
>        bpf_prog_2c29ac5cdc6b1842+0x43/0x47
>        bpf_dispatcher_nop_func include/linux/bpf.h:1290 [inline]
>        __bpf_prog_run include/linux/filter.h:701 [inline]
>        bpf_prog_run include/linux/filter.h:708 [inline]
>        __bpf_trace_run kernel/trace/bpf_trace.c:2351 [inline]
>        bpf_trace_run2+0x231/0x590 kernel/trace/bpf_trace.c:2392
>        __bpf_trace_contention_begin+0xca/0x110 include/trace/events/lock.h:95
>        __traceiter_contention_begin+0x5a/0xa0 include/trace/events/lock.h:95
>        __preempt_count_dec_and_test arch/x86/include/asm/preempt.h:94 [inline]
>        class_preempt_notrace_destructor include/linux/preempt.h:481 [inline]
>        trace_contention_begin.constprop.0+0xf3/0x170 include/trace/events/lock.h:95
>        __pv_queued_spin_lock_slowpath+0x10b/0xc90 kernel/locking/qspinlock.c:402
>        pv_queued_spin_lock_slowpath arch/x86/include/asm/paravirt.h:584 [inline]
>        queued_spin_lock_slowpath arch/x86/include/asm/qspinlock.h:51 [inline]
>        queued_spin_lock include/asm-generic/qspinlock.h:114 [inline]
>        do_raw_spin_lock+0x210/0x2c0 kernel/locking/spinlock_debug.c:116
>        htab_lock_bucket kernel/bpf/hashtab.c:167 [inline]
>        htab_lru_map_delete_elem+0x1c8/0x790 kernel/bpf/hashtab.c:1484
>        bpf_prog_2c29ac5cdc6b1842+0x43/0x47
>        bpf_dispatcher_nop_func include/linux/bpf.h:1290 [inline]
>        __bpf_prog_run include/linux/filter.h:701 [inline]
>        bpf_prog_run include/linux/filter.h:708 [inline]
>        __bpf_trace_run kernel/trace/bpf_trace.c:2351 [inline]
>        bpf_trace_run2+0x231/0x590 kernel/trace/bpf_trace.c:2392
>        __bpf_trace_contention_begin+0xca/0x110 include/trace/events/lock.h:95
>        __traceiter_contention_begin+0x5a/0xa0 include/trace/events/lock.h:95
>        trace_contention_begin+0xd2/0x140 include/trace/events/lock.h:95
>        __mutex_lock_common kernel/locking/mutex.c:587 [inline]
>        __mutex_lock+0x1a8/0xa60 kernel/locking/mutex.c:735
>        uprobe_clear_state+0x4b/0x1a0 kernel/events/uprobes.c:1771
>        __mmput+0x79/0x4c0 kernel/fork.c:1349
>        mmput+0x62/0x70 kernel/fork.c:1375
>        exit_mm kernel/exit.c:570 [inline]
>        do_exit+0x9bf/0x2d70 kernel/exit.c:925
>        do_group_exit+0xd3/0x2a0 kernel/exit.c:1087
>        __do_sys_exit_group kernel/exit.c:1098 [inline]
>        __se_sys_exit_group kernel/exit.c:1096 [inline]
>        __x64_sys_exit_group+0x3e/0x50 kernel/exit.c:1096
>        x64_sys_call+0x151f/0x1720 arch/x86/include/generated/asm/syscalls_64.h:232
>        do_syscall_x64 arch/x86/entry/common.c:52 [inline]
>        do_syscall_64+0xcd/0x250 arch/x86/entry/common.c:83
>        entry_SYSCALL_64_after_hwframe+0x77/0x7f
>
> other info that might help us debug this:
>
>  Possible unsafe locking scenario:
>
>        CPU0                    CPU1
>        ----                    ----
>   lock(&htab->lockdep_key#435);
>                                lock(&htab->lockdep_key#434);
>                                lock(&htab->lockdep_key#435);
>   lock(&htab->lockdep_key#434);
>
>  *** DEADLOCK ***
>
> 4 locks held by syz-executor207/6807:
>  #0: ffffffff8e2d69e8 (delayed_uprobe_lock){+.+.}-{4:4}, at: uprobe_clear_state+0x4b/0x1a0 kernel/events/uprobes.c:1771
>  #1: ffffffff8e1bb500 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:337 [inline]
>  #1: ffffffff8e1bb500 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:849 [inline]
>  #1: ffffffff8e1bb500 (rcu_read_lock){....}-{1:3}, at: __bpf_trace_run kernel/trace/bpf_trace.c:2350 [inline]
>  #1: ffffffff8e1bb500 (rcu_read_lock){....}-{1:3}, at: bpf_trace_run2+0x1c2/0x590 kernel/trace/bpf_trace.c:2392
>  #2: ffff888031440e20 (&htab->lockdep_key#435){....}-{2:2}, at: htab_lock_bucket kernel/bpf/hashtab.c:167 [inline]
>  #2: ffff888031440e20 (&htab->lockdep_key#435){....}-{2:2}, at: htab_lru_map_delete_elem+0x1c8/0x790 kernel/bpf/hashtab.c:1484
>  #3: ffffffff8e1bb500 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:337 [inline]
>  #3: ffffffff8e1bb500 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:849 [inline]
>  #3: ffffffff8e1bb500 (rcu_read_lock){....}-{1:3}, at: __bpf_trace_run kernel/trace/bpf_trace.c:2350 [inline]
>  #3: ffffffff8e1bb500 (rcu_read_lock){....}-{1:3}, at: bpf_trace_run2+0x1c2/0x590 kernel/trace/bpf_trace.c:2392
>
> stack backtrace:
> CPU: 3 UID: 0 PID: 6807 Comm: syz-executor207 Not tainted 6.13.0-rc1-syzkaller-00025-gfeffde684ac2 #0
> Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2~bpo12+1 04/01/2014
> Call Trace:
>  <TASK>
>  __dump_stack lib/dump_stack.c:94 [inline]
>  dump_stack_lvl+0x116/0x1f0 lib/dump_stack.c:120
>  print_circular_bug+0x419/0x5d0 kernel/locking/lockdep.c:2074
>  check_noncircular+0x31a/0x400 kernel/locking/lockdep.c:2206
>  check_prev_add kernel/locking/lockdep.c:3161 [inline]
>  check_prevs_add kernel/locking/lockdep.c:3280 [inline]
>  validate_chain kernel/locking/lockdep.c:3904 [inline]
>  __lock_acquire+0x249e/0x3c40 kernel/locking/lockdep.c:5226
>  lock_acquire.part.0+0x11b/0x380 kernel/locking/lockdep.c:5849
>  __raw_spin_lock include/linux/spinlock_api_smp.h:133 [inline]
>  _raw_spin_lock+0x2e/0x40 kernel/locking/spinlock.c:154
>  htab_lock_bucket kernel/bpf/hashtab.c:167 [inline]
>  htab_lru_map_delete_elem+0x1c8/0x790 kernel/bpf/hashtab.c:1484
>  bpf_prog_2c29ac5cdc6b1842+0x43/0x47
>  bpf_dispatcher_nop_func include/linux/bpf.h:1290 [inline]
>  __bpf_prog_run include/linux/filter.h:701 [inline]
>  bpf_prog_run include/linux/filter.h:708 [inline]
>  __bpf_trace_run kernel/trace/bpf_trace.c:2351 [inline]
>  bpf_trace_run2+0x231/0x590 kernel/trace/bpf_trace.c:2392
>  __bpf_trace_contention_begin+0xca/0x110 include/trace/events/lock.h:95
>  __traceiter_contention_begin+0x5a/0xa0 include/trace/events/lock.h:95
>  __preempt_count_dec_and_test arch/x86/include/asm/preempt.h:94 [inline]
>  class_preempt_notrace_destructor include/linux/preempt.h:481 [inline]
>  trace_contention_begin.constprop.0+0xf3/0x170 include/trace/events/lock.h:95
>  __pv_queued_spin_lock_slowpath+0x10b/0xc90 kernel/locking/qspinlock.c:402
>  pv_queued_spin_lock_slowpath arch/x86/include/asm/paravirt.h:584 [inline]
>  queued_spin_lock_slowpath arch/x86/include/asm/qspinlock.h:51 [inline]
>  queued_spin_lock include/asm-generic/qspinlock.h:114 [inline]
>  do_raw_spin_lock+0x210/0x2c0 kernel/locking/spinlock_debug.c:116
>  htab_lock_bucket kernel/bpf/hashtab.c:167 [inline]
>  htab_lru_map_delete_elem+0x1c8/0x790 kernel/bpf/hashtab.c:1484
>  bpf_prog_2c29ac5cdc6b1842+0x43/0x47
>  bpf_dispatcher_nop_func include/linux/bpf.h:1290 [inline]
>  __bpf_prog_run include/linux/filter.h:701 [inline]
>  bpf_prog_run include/linux/filter.h:708 [inline]
>  __bpf_trace_run kernel/trace/bpf_trace.c:2351 [inline]
>  bpf_trace_run2+0x231/0x590 kernel/trace/bpf_trace.c:2392
>  __bpf_trace_contention_begin+0xca/0x110 include/trace/events/lock.h:95
>  __traceiter_contention_begin+0x5a/0xa0 include/trace/events/lock.h:95
>  trace_contention_begin+0xd2/0x140 include/trace/events/lock.h:95
>  __mutex_lock_common kernel/locking/mutex.c:587 [inline]
>  __mutex_lock+0x1a8/0xa60 kernel/locking/mutex.c:735
>  uprobe_clear_state+0x4b/0x1a0 kernel/events/uprobes.c:1771
>  __mmput+0x79/0x4c0 kernel/fork.c:1349
>  mmput+0x62/0x70 kernel/fork.c:1375
>  exit_mm kernel/exit.c:570 [inline]
>  do_exit+0x9bf/0x2d70 kernel/exit.c:925
>  do_group_exit+0xd3/0x2a0 kernel/exit.c:1087
>  __do_sys_exit_group kernel/exit.c:1098 [inline]
>  __se_sys_exit_group kernel/exit.c:1096 [inline]
>  __x64_sys_exit_group+0x3e/0x50 kernel/exit.c:1096
>  x64_sys_call+0x151f/0x1720 arch/x86/include/generated/asm/syscalls_64.h:232
>  do_syscall_x64 arch/x86/entry/common.c:52 [inline]
>  do_syscall_64+0xcd/0x250 arch/x86/entry/common.c:83
>  entry_SYSCALL_64_after_hwframe+0x77/0x7f
> RIP: 0033:0x7fe3838cedf9
> Code: Unable to access opcode bytes at 0x7fe3838cedcf.
> RSP: 002b:00007ffd9c887888 EFLAGS: 00000246 ORIG_RAX: 00000000000000e7
> RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007fe3838cedf9
> RDX: 000000000000003c RSI: 00000000000000e7 RDI: 0000000000000000
> RBP: 00007fe38395b390 R08: ffffffffffffffb0 R09: 00007ffd9c887910
> R10: 00007ffd9c887910 R11: 0000000000000246 R12: 00007fe38395b390
> R13: 0000000000000000 R14: 00007fe38395bf20 R15: 00007fe38389c900
>  </TASK>
>
>
> ---
> This report is generated by a bot. It may contain errors.
> See https://goo.gl/tpsmEJ for more information about syzbot.
> syzbot engineers can be reached at syzkaller@...glegroups.com.
>
> syzbot will keep track of this issue. See:
> https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
>
> If the report is already addressed, let syzbot know by replying with:
> #syz fix: exact-commit-title
>
> 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.
>
> If you want to overwrite report's subsystems, reply with:
> #syz set subsystems: new-subsystem
> (See the list of subsystem names on the web dashboard)
>
> If the report is a duplicate of another one, reply with:
> #syz dup: exact-subject-of-another-report
>
> If you want to undo deduplication, reply with:
> #syz undup

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