linux-kernel - Re: [syzbot] [bpf?] possible deadlock in __stack_map

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Date: Thu, 18 Apr 2024 22:06:05 -0700
From: syzbot <syzbot+dddd99ae26c656485d89@...kaller.appspotmail.com>
To: hdanton@...a.com, linux-kernel@...r.kernel.org, 
	syzkaller-bugs@...glegroups.com
Subject: Re: [syzbot] [bpf?] possible deadlock in __stack_map_get

Hello,

syzbot has tested the proposed patch but the reproducer is still triggering an issue:
possible deadlock in __stack_map_get

============================================
WARNING: possible recursive locking detected
6.8.0-syzkaller-05271-gf99c5f563c17-dirty #0 Not tainted
--------------------------------------------
syz-executor.3/6102 is trying to acquire lock:
ffff88806da7b1d8 (&qs->lock){-.-.}-{2:2}, at: __stack_map_get+0x286/0x6f0 kernel/bpf/queue_stack_maps.c:148

but task is already holding lock:
ffff88807eace1d8 (&qs->lock){-.-.}-{2:2}, at: __stack_map_get+0x286/0x6f0 kernel/bpf/queue_stack_maps.c:148

other info that might help us debug this:
 Possible unsafe locking scenario:

       CPU0
       ----
  lock(&qs->lock);
  lock(&qs->lock);

 *** DEADLOCK ***

 May be due to missing lock nesting notation

4 locks held by syz-executor.3/6102:
 #0: ffffffff8e17cf88 (tracepoints_mutex){+.+.}-{3:3}, at: tracepoint_probe_unregister+0x32/0x990 kernel/tracepoint.c:548
 #1: ffffffff8e131920 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire include/linux/rcupdate.h:329 [inline]
 #1: ffffffff8e131920 (rcu_read_lock){....}-{1:2}, at: rcu_read_lock include/linux/rcupdate.h:781 [inline]
 #1: ffffffff8e131920 (rcu_read_lock){....}-{1:2}, at: __bpf_trace_run kernel/trace/bpf_trace.c:2380 [inline]
 #1: ffffffff8e131920 (rcu_read_lock){....}-{1:2}, at: bpf_trace_run2+0x114/0x420 kernel/trace/bpf_trace.c:2420
 #2: ffff88807eace1d8 (&qs->lock){-.-.}-{2:2}, at: __stack_map_get+0x286/0x6f0 kernel/bpf/queue_stack_maps.c:148
 #3: ffffffff8e131920 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire include/linux/rcupdate.h:329 [inline]
 #3: ffffffff8e131920 (rcu_read_lock){....}-{1:2}, at: rcu_read_lock include/linux/rcupdate.h:781 [inline]
 #3: ffffffff8e131920 (rcu_read_lock){....}-{1:2}, at: __bpf_trace_run kernel/trace/bpf_trace.c:2380 [inline]
 #3: ffffffff8e131920 (rcu_read_lock){....}-{1:2}, at: bpf_trace_run2+0x114/0x420 kernel/trace/bpf_trace.c:2420

stack backtrace:
CPU: 0 PID: 6102 Comm: syz-executor.3 Not tainted 6.8.0-syzkaller-05271-gf99c5f563c17-dirty #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+0x1e7/0x2e0 lib/dump_stack.c:106
 check_deadlock kernel/locking/lockdep.c:3062 [inline]
 validate_chain+0x15c1/0x58e0 kernel/locking/lockdep.c:3856
 __lock_acquire+0x1346/0x1fd0 kernel/locking/lockdep.c:5137
 lock_acquire+0x1e4/0x530 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
 __stack_map_get+0x286/0x6f0 kernel/bpf/queue_stack_maps.c:148
 bpf_prog_7a16b54e5ee857f9+0x42/0x46
 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_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+0x272/0x370 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
 __stack_map_get+0x286/0x6f0 kernel/bpf/queue_stack_maps.c:148
 bpf_prog_7a16b54e5ee857f9+0x42/0x46
 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_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+0x2e5/0xd70 kernel/locking/mutex.c:752
 tracepoint_probe_unregister+0x32/0x990 kernel/tracepoint.c:548
 bpf_raw_tp_link_release+0x63/0x90 kernel/bpf/syscall.c:3482
 bpf_link_free kernel/bpf/syscall.c:3033 [inline]
 bpf_link_put_direct+0x123/0x1b0 kernel/bpf/syscall.c:3064
 bpf_link_release+0x3b/0x50 kernel/bpf/syscall.c:3071
 __fput+0x429/0x8a0 fs/file_table.c:423
 __do_sys_close fs/open.c:1557 [inline]
 __se_sys_close fs/open.c:1542 [inline]
 __x64_sys_close+0x7f/0x110 fs/open.c:1542
 do_syscall_64+0xfb/0x240
 entry_SYSCALL_64_after_hwframe+0x6d/0x75
RIP: 0033:0x7f7e74c7cd5a
Code: 48 3d 00 f0 ff ff 77 48 c3 0f 1f 80 00 00 00 00 48 83 ec 18 89 7c 24 0c e8 03 7f 02 00 8b 7c 24 0c 89 c2 b8 03 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 36 89 d7 89 44 24 0c e8 63 7f 02 00 8b 44 24
RSP: 002b:00007ffc624e2df0 EFLAGS: 00000293 ORIG_RAX: 0000000000000003
RAX: ffffffffffffffda RBX: 0000000000000006 RCX: 00007f7e74c7cd5a
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000005
RBP: 0000000000000226 R08: 0000001b2f460000 R09: 00007f7e74dabf8c
R10: 00007ffc624e2f40 R11: 0000000000000293 R12: 00007f7e74801260
R13: ffffffffffffffff R14: 00007f7e74800000 R15: 0000000000019ae9
 </TASK>


Tested on:

commit:         f99c5f56 Merge tag 'nf-24-03-21' of git://git.kernel.o..
git tree:       https://git.kernel.org/pub/scm/linux/kernel/git/netdev/net.git
console output: https://syzkaller.appspot.com/x/log.txt?x=124f9ae7180000
kernel config:  https://syzkaller.appspot.com/x/.config?x=6fb1be60a193d440
dashboard link: https://syzkaller.appspot.com/bug?extid=dddd99ae26c656485d89
compiler:       Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
patch:          https://syzkaller.appspot.com/x/patch.diff?x=10257bb3180000