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

[Hillf Danton]

On Tue, 12 Mar 2024 22:02:27 +0100 Jiri Olsa <olsajiri@xxxxxxxxx>
> 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,
> will try to reproduce

Feel free to take a look at another syzbot report [1,2]

[1] Subject: Re: [syzbot] [ntfs3?] possible deadlock in ntfs_set_state (2)
https://lore.kernel.org/lkml/ZdwSXCaTrzq7mm7Z@boqun-archlinux/

[2] Subject: Re: [syzbot] [bpf?] possible deadlock in __bpf_ringbuf_reserve
https://lore.kernel.org/lkml/00000000000082883f061388d49e@xxxxxxxxxx/