Re: [syzbot] [bpf?] possible deadlock in __bpf_ringbuf_reserve

From: Jiri Olsa
Date: Tue Mar 12 2024 - 17:18:39 EST

Next message: Samuel Holland: "[PATCH] riscv: Add tracepoints for SBI calls and returns"
Previous message: Paul E. McKenney: "Re: Unexplained long boot delays [Was Re: [GIT PULL] RCU changes for v6.9]"
In reply to: Jiri Olsa: "Re: [syzbot] [bpf?] possible deadlock in __bpf_ringbuf_reserve"
Next in thread: Andrii Nakryiko: "Re: [syzbot] [bpf?] possible deadlock in __bpf_ringbuf_reserve"
Messages sorted by: [ date ] [ thread ] [ subject ] [ author ]

On Tue, Mar 12, 2024 at 10:02:27PM +0100, Jiri Olsa wrote:
> On Tue, Mar 12, 2024 at 09:41:26AM -0700, syzbot wrote:
> > Hello,
> >
> > syzbot found the following issue on:
> >
> > HEAD commit: df4793505abd Merge tag 'net-6.8-rc8' of git://git.kernel.o..
> > git tree: bpf
> > console+strace: https://syzkaller.appspot.com/x/log.txt?x=11fd0092180000
> > kernel config: https://syzkaller.appspot.com/x/.config?x=c11c5c676adb61f0
> > dashboard link: https://syzkaller.appspot.com/bug?extid=850aaf14624dc0c6d366
> > 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=1509c4ae180000
> > C reproducer: https://syzkaller.appspot.com/x/repro.c?x=10babc01180000
> >
> > Downloadable assets:
> > disk image: https://storage.googleapis.com/syzbot-assets/d2e80ee1112b/disk-df479350.raw.xz
> > vmlinux: https://storage.googleapis.com/syzbot-assets/b35ea54cd190/vmlinux-df479350.xz
> > kernel image: https://storage.googleapis.com/syzbot-assets/59f69d999ad2/bzImage-df479350.xz
> >
> > IMPORTANT: if you fix the issue, please add the following tag to the commit:
> > Reported-by: syzbot+850aaf14624dc0c6d366@xxxxxxxxxxxxxxxxxxxxxxxxx
> >
> > ============================================
> > WARNING: possible recursive locking detected
> > 6.8.0-rc7-syzkaller-gdf4793505abd #0 Not tainted
> > --------------------------------------------
> > strace-static-x/5063 is trying to acquire lock:
> > ffffc900096f10d8 (&rb->spinlock){-.-.}-{2:2}, at: __bpf_ringbuf_reserve+0x211/0x4f0 kernel/bpf/ringbuf.c:424
> >
> > but task is already holding lock:
> > ffffc900098410d8 (&rb->spinlock){-.-.}-{2:2}, at: __bpf_ringbuf_reserve+0x211/0x4f0 kernel/bpf/ringbuf.c:424
> >
> > other info that might help us debug this:
> > Possible unsafe locking scenario:
> >
> > CPU0
> > ----
> > lock(&rb->spinlock);
> > lock(&rb->spinlock);
> >
> > *** DEADLOCK ***
> >
> > May be due to missing lock nesting notation
> >
> > 4 locks held by strace-static-x/5063:
> > #0: ffff88807857e068 (&pipe->mutex/1){+.+.}-{3:3}, at: __pipe_lock fs/pipe.c:103 [inline]
> > #0: ffff88807857e068 (&pipe->mutex/1){+.+.}-{3:3}, at: pipe_write+0x1cc/0x1a40 fs/pipe.c:465
> > #1: ffffffff8e130be0 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire include/linux/rcupdate.h:298 [inline]
> > #1: ffffffff8e130be0 (rcu_read_lock){....}-{1:2}, at: rcu_read_lock include/linux/rcupdate.h:750 [inline]
> > #1: ffffffff8e130be0 (rcu_read_lock){....}-{1:2}, at: __bpf_trace_run kernel/trace/bpf_trace.c:2380 [inline]
> > #1: ffffffff8e130be0 (rcu_read_lock){....}-{1:2}, at: bpf_trace_run2+0x114/0x420 kernel/trace/bpf_trace.c:2420
> > #2: ffffc900098410d8 (&rb->spinlock){-.-.}-{2:2}, at: __bpf_ringbuf_reserve+0x211/0x4f0 kernel/bpf/ringbuf.c:424
> > #3: ffffffff8e130be0 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire include/linux/rcupdate.h:298 [inline]
> > #3: ffffffff8e130be0 (rcu_read_lock){....}-{1:2}, at: rcu_read_lock include/linux/rcupdate.h:750 [inline]
> > #3: ffffffff8e130be0 (rcu_read_lock){....}-{1:2}, at: __bpf_trace_run kernel/trace/bpf_trace.c:2380 [inline]
> > #3: ffffffff8e130be0 (rcu_read_lock){....}-{1:2}, at: bpf_trace_run2+0x114/0x420 kernel/trace/bpf_trace.c:2420
> >
> > stack backtrace:
> > CPU: 0 PID: 5063 Comm: strace-static-x Not tainted 6.8.0-rc7-syzkaller-gdf4793505abd #0
> > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/25/2024
> > Call Trace:
> > <TASK>
> > __dump_stack lib/dump_stack.c:88 [inline]
> > dump_stack_lvl+0x1e7/0x2e0 lib/dump_stack.c:106
> > check_deadlock kernel/locking/lockdep.c:3062 [inline]
> > validate_chain+0x15c0/0x58e0 kernel/locking/lockdep.c:3856
> > __lock_acquire+0x1345/0x1fd0 kernel/locking/lockdep.c:5137
> > lock_acquire+0x1e3/0x530 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
> > __bpf_ringbuf_reserve+0x211/0x4f0 kernel/bpf/ringbuf.c:424
> > ____bpf_ringbuf_reserve kernel/bpf/ringbuf.c:459 [inline]
> > bpf_ringbuf_reserve+0x5c/0x70 kernel/bpf/ringbuf.c:451
> > bpf_prog_9efe54833449f08e+0x2d/0x47
> > bpf_dispatcher_nop_func include/linux/bpf.h:1231 [inline]
> > __bpf_prog_run include/linux/filter.h:651 [inline]
> > bpf_prog_run include/linux/filter.h:658 [inline]
> > __bpf_trace_run kernel/trace/bpf_trace.c:2381 [inline]
>
> hum, scratching my head how this could passed through the prog->active check,

nah could be 2 instances of the same program, got confused by the tag

trace_contention_end
__bpf_trace_run(prog1)
bpf_prog_9efe54833449f08e
bpf_ringbuf_reserve
trace_contention_end
__bpf_trace_run(prog1) prog1->active check fails
__bpf_trace_run(prog2)
bpf_prog_9efe54833449f08e
bpf_ringbuf_reserve
lockup

we had similar issue in [1] and we replaced the lock with extra buffers,
not sure that's possible in bpf_ringbuf_reserve

jirka

[1] e2bb9e01d589 bpf: Remove trace_printk_lock

> will try to reproduce
>
> jirka
>
> > bpf_trace_run2+0x204/0x420 kernel/trace/bpf_trace.c:2420
> > __traceiter_contention_end+0x7b/0xb0 include/trace/events/lock.h:122
> > trace_contention_end+0xf6/0x120 include/trace/events/lock.h:122
> > __pv_queued_spin_lock_slowpath+0x939/0xc60 kernel/locking/qspinlock.c:560
> > pv_queued_spin_lock_slowpath arch/x86/include/asm/paravirt.h:584 [inline]
> > queued_spin_lock_slowpath+0x42/0x50 arch/x86/include/asm/qspinlock.h:51
> > queued_spin_lock include/asm-generic/qspinlock.h:114 [inline]
> > do_raw_spin_lock+0x271/0x370 kernel/locking/spinlock_debug.c:116
> > __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:111 [inline]
> > _raw_spin_lock_irqsave+0xe1/0x120 kernel/locking/spinlock.c:162
> > __bpf_ringbuf_reserve+0x211/0x4f0 kernel/bpf/ringbuf.c:424
> > ____bpf_ringbuf_reserve kernel/bpf/ringbuf.c:459 [inline]
> > bpf_ringbuf_reserve+0x5c/0x70 kernel/bpf/ringbuf.c:451
> > bpf_prog_9efe54833449f08e+0x2d/0x47
> > bpf_dispatcher_nop_func include/linux/bpf.h:1231 [inline]
> > __bpf_prog_run include/linux/filter.h:651 [inline]
> > bpf_prog_run include/linux/filter.h:658 [inline]
> > __bpf_trace_run kernel/trace/bpf_trace.c:2381 [inline]
> > bpf_trace_run2+0x204/0x420 kernel/trace/bpf_trace.c:2420
> > __traceiter_contention_end+0x7b/0xb0 include/trace/events/lock.h:122
> > trace_contention_end+0xd7/0x100 include/trace/events/lock.h:122
> > __mutex_lock_common kernel/locking/mutex.c:617 [inline]
> > __mutex_lock+0x2e4/0xd70 kernel/locking/mutex.c:752
> > __pipe_lock fs/pipe.c:103 [inline]
> > pipe_write+0x1cc/0x1a40 fs/pipe.c:465
> > call_write_iter include/linux/fs.h:2087 [inline]
> > new_sync_write fs/read_write.c:497 [inline]
> > vfs_write+0xa81/0xcb0 fs/read_write.c:590
> > ksys_write+0x1a0/0x2c0 fs/read_write.c:643
> > do_syscall_64+0xf9/0x240
> > entry_SYSCALL_64_after_hwframe+0x6f/0x77
> > RIP: 0033:0x4e8593
> > Code: c7 c2 a8 ff ff ff f7 d8 64 89 02 48 c7 c0 ff ff ff ff eb b7 0f 1f 00 64 8b 04 25 18 00 00 00 85 c0 75 14 b8 01 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 55 c3 0f 1f 40 00 48 83 ec 28 48 89 54 24 18
> > RSP: 002b:00007ffeda768928 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
> > RAX: ffffffffffffffda RBX: 0000000000000012 RCX: 00000000004e8593
> > RDX: 0000000000000012 RSI: 0000000000817140 RDI: 0000000000000002
> > RBP: 0000000000817140 R08: 0000000000000010 R09: 0000000000000090
> > R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000012
> > R13: 000000000063f460 R14: 0000000000000012 R15: 0000000000000001
> > </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@xxxxxxxxxxxxxxxx.
> >
> > 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

Next message: Samuel Holland: "[PATCH] riscv: Add tracepoints for SBI calls and returns"
Previous message: Paul E. McKenney: "Re: Unexplained long boot delays [Was Re: [GIT PULL] RCU changes for v6.9]"
In reply to: Jiri Olsa: "Re: [syzbot] [bpf?] possible deadlock in __bpf_ringbuf_reserve"
Next in thread: Andrii Nakryiko: "Re: [syzbot] [bpf?] possible deadlock in __bpf_ringbuf_reserve"
Messages sorted by: [ date ] [ thread ] [ subject ] [ author ]