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* WARNING: bad unlock balance in rcu_lock_release
@ 2019-06-23 12:37 syzbot
  2019-10-13 21:28 ` syzbot
  2020-04-30  6:15 ` syzbot
  0 siblings, 2 replies; 5+ messages in thread
From: syzbot @ 2019-06-23 12:37 UTC (permalink / raw)
  To: linux-fsdevel, linux-kernel, syzkaller-bugs, viro

Hello,

syzbot found the following crash on:

HEAD commit:    bed3c0d8 Merge tag 'for-5.2-rc5-tag' of git://git.kernel.o..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=148ef681a00000
kernel config:  https://syzkaller.appspot.com/x/.config?x=28ec3437a5394ee0
dashboard link: https://syzkaller.appspot.com/bug?extid=f9545ab3e9f85cd43a3a
compiler:       clang version 9.0.0 (/home/glider/llvm/clang  
80fee25776c2fb61e74c1ecb1a523375c2500b69)

Unfortunately, I don't have any reproducer for this crash yet.

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+f9545ab3e9f85cd43a3a@syzkaller.appspotmail.com

=====================================
WARNING: bad unlock balance detected!
5.2.0-rc5+ #3 Not tainted
-------------------------------------
syz-executor.3/1203 is trying to release lock (rcu_callback) at:
[<ffffffff81636ec4>] rcu_lock_release+0x4/0x20 include/linux/rcupdate.h:212
but there are no more locks to release!

other info that might help us debug this:
1 lock held by syz-executor.3/1203:
  #0: 00000000ae396ab9 (&type->s_umount_key#48/1){+.+.}, at:  
alloc_super+0x15f/0x740 fs/super.c:228

stack backtrace:
CPU: 0 PID: 1203 Comm: syz-executor.3 Not tainted 5.2.0-rc5+ #3
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS  
Google 01/01/2011
Call Trace:
  <IRQ>
  __dump_stack lib/dump_stack.c:77 [inline]
  dump_stack+0x1d8/0x2f8 lib/dump_stack.c:113
  print_unlock_imbalance_bug+0x26d/0x2b0 kernel/locking/lockdep.c:3846
  __lock_release kernel/locking/lockdep.c:4062 [inline]
  lock_release+0x435/0x790 kernel/locking/lockdep.c:4322
  rcu_lock_release+0x1c/0x20 include/linux/rcupdate.h:214
  __rcu_reclaim kernel/rcu/rcu.h:223 [inline]
  rcu_do_batch kernel/rcu/tree.c:2092 [inline]
  invoke_rcu_callbacks kernel/rcu/tree.c:2310 [inline]
  rcu_core+0x8e2/0xf90 kernel/rcu/tree.c:2291
  __do_softirq+0x340/0x7b0 arch/x86/include/asm/paravirt.h:777
  invoke_softirq kernel/softirq.c:373 [inline]
  irq_exit+0x21a/0x230 kernel/softirq.c:413
  exiting_irq arch/x86/include/asm/apic.h:536 [inline]
  smp_apic_timer_interrupt+0xf8/0x260 arch/x86/kernel/apic/apic.c:1068
  apic_timer_interrupt+0xf/0x20 arch/x86/entry/entry_64.S:806
  </IRQ>
RIP: 0010:arch_local_irq_restore arch/x86/include/asm/paravirt.h:767  
[inline]
RIP: 0010:console_unlock+0xa65/0xf20 kernel/printk/printk.c:2471
Code: 20 00 74 0c 48 c7 c7 90 63 aa 88 e8 a5 44 50 00 48 83 3d fd cc 4b 07  
00 0f 84 7d 04 00 00 e8 52 1b 17 00 48 8b 7c 24 28 57 9d <0f> 1f 44 00 00  
f6 44 24 1f 01 75 52 e8 3a 1b 17 00 eb 63 0f 1f 84
RSP: 0018:ffff88805b6c7540 EFLAGS: 00000282 ORIG_RAX: ffffffffffffff13
RAX: ffffffff815e969e RBX: 0000000000000200 RCX: 0000000000040000
RDX: ffffc9000c450000 RSI: 000000000002643c RDI: 0000000000000282
RBP: ffff88805b6c7670 R08: ffff88805cb14040 R09: fffffbfff115a505
R10: fffffbfff115a505 R11: 1ffffffff115a504 R12: dffffc0000000000
R13: 0000000000000000 R14: 0000000000000000 R15: ffffffff88c31298
  vprintk_emit+0x239/0x3a0 kernel/printk/printk.c:1986
  vprintk_default+0x28/0x30 kernel/printk/printk.c:2013
  vprintk_func+0x158/0x170 kernel/printk/printk_safe.c:386
  printk+0xc4/0x11d kernel/printk/printk.c:2046
  __ntfs_error+0x21b/0x230 fs/ntfs/debug.c:89
  parse_options+0x481/0x1f80 fs/ntfs/super.c:234
  ntfs_fill_super+0x19b/0x2940 fs/ntfs/super.c:2748
  mount_bdev+0x31c/0x440 fs/super.c:1346
  ntfs_mount+0x34/0x40 fs/ntfs/super.c:3051
  legacy_get_tree+0xf9/0x1a0 fs/fs_context.c:661
  vfs_get_tree+0x8f/0x360 fs/super.c:1476
  do_new_mount fs/namespace.c:2791 [inline]
  do_mount+0x1813/0x2730 fs/namespace.c:3111
  ksys_mount+0xcc/0x100 fs/namespace.c:3320
  __do_sys_mount fs/namespace.c:3334 [inline]
  __se_sys_mount fs/namespace.c:3331 [inline]
  __x64_sys_mount+0xbf/0xd0 fs/namespace.c:3331
  do_syscall_64+0xfe/0x140 arch/x86/entry/common.c:301
  entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x45bd1a
Code: b8 a6 00 00 00 0f 05 48 3d 01 f0 ff ff 0f 83 9d 8d fb ff c3 66 2e 0f  
1f 84 00 00 00 00 00 66 90 49 89 ca b8 a5 00 00 00 0f 05 <48> 3d 01 f0 ff  
ff 0f 83 7a 8d fb ff c3 66 0f 1f 84 00 00 00 00 00
RSP: 002b:00007f49071c9a88 EFLAGS: 00000206 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 00007f49071c9b40 RCX: 000000000045bd1a
RDX: 00007f49071c9ae0 RSI: 0000000020000140 RDI: 00007f49071c9b00
RBP: 0000000000000000 R08: 00007f49071c9b40 R09: 00007f49071c9ae0
R10: 0000000000000000 R11: 0000000000000206 R12: 0000000000000003
R13: 00000000004c82e2 R14: 00000000004deb40 R15: 00000000ffffffff
protocol 88fb is buggy, dev hsr_slave_0
protocol 88fb is buggy, dev hsr_slave_1
protocol 88fb is buggy, dev hsr_slave_0
protocol 88fb is buggy, dev hsr_slave_1
protocol 88fb is buggy, dev hsr_slave_1
protocol 88fb is buggy, dev hsr_slave_0
protocol 88fb is buggy, dev hsr_slave_1
protocol 88fb is buggy, dev hsr_slave_0
protocol 88fb is buggy, dev hsr_slave_1
protocol 88fb is buggy, dev hsr_slave_0
protocol 88fb is buggy, dev hsr_slave_1
protocol 88fb is buggy, dev hsr_slave_0
net_ratelimit: 21 callbacks suppressed
protocol 88fb is buggy, dev hsr_slave_0
protocol 88fb is buggy, dev hsr_slave_1
protocol 88fb is buggy, dev hsr_slave_0
protocol 88fb is buggy, dev hsr_slave_1


---
This bug 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@googlegroups.com.

syzbot will keep track of this bug report. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.

^ permalink raw reply	[flat|nested] 5+ messages in thread
* Re: WARNING: bad unlock balance in rcu_lock_release
  2019-06-23 12:37 WARNING: bad unlock balance in rcu_lock_release syzbot
@ 2019-10-13 21:28 ` syzbot
  2019-10-15  7:56   ` Jan Kara
  2020-04-30  6:15 ` syzbot
  1 sibling, 1 reply; 5+ messages in thread
From: syzbot @ 2019-10-13 21:28 UTC (permalink / raw)
  To: linux-fsdevel, linux-kernel, syzkaller-bugs, viro

syzbot has found a reproducer for the following crash on:

HEAD commit:    da940012 Merge tag 'char-misc-5.4-rc3' of git://git.kernel..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=12cfdf4f600000
kernel config:  https://syzkaller.appspot.com/x/.config?x=2d2fd92a28d3e50
dashboard link: https://syzkaller.appspot.com/bug?extid=f9545ab3e9f85cd43a3a
compiler:       clang version 9.0.0 (/home/glider/llvm/clang  
80fee25776c2fb61e74c1ecb1a523375c2500b69)
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=148c9fc7600000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=100d3f8b600000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+f9545ab3e9f85cd43a3a@syzkaller.appspotmail.com

=====================================
WARNING: bad unlock balance detected!
5.4.0-rc2+ #0 Not tainted
-------------------------------------
syz-executor111/7877 is trying to release lock (rcu_callback) at:
[<ffffffff81612bd4>] rcu_lock_release+0x4/0x20 include/linux/rcupdate.h:212
but there are no more locks to release!

other info that might help us debug this:
1 lock held by syz-executor111/7877:
  #0: ffff8880a3c600d8 (&type->s_umount_key#42/1){+.+.}, at:  
alloc_super+0x15f/0x790 fs/super.c:229

stack backtrace:
CPU: 1 PID: 7877 Comm: syz-executor111 Not tainted 5.4.0-rc2+ #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS  
Google 01/01/2011
Call Trace:
  <IRQ>
  __dump_stack lib/dump_stack.c:77 [inline]
  dump_stack+0x1d8/0x2f8 lib/dump_stack.c:113
  print_unlock_imbalance_bug+0x20b/0x240 kernel/locking/lockdep.c:4008
  __lock_release kernel/locking/lockdep.c:4244 [inline]
  lock_release+0x473/0x780 kernel/locking/lockdep.c:4506
  rcu_lock_release+0x1c/0x20 include/linux/rcupdate.h:214
  __rcu_reclaim kernel/rcu/rcu.h:223 [inline]
  rcu_do_batch kernel/rcu/tree.c:2157 [inline]
  rcu_core+0x84f/0x1050 kernel/rcu/tree.c:2377
  rcu_core_si+0x9/0x10 kernel/rcu/tree.c:2386
  __do_softirq+0x333/0x7c4 arch/x86/include/asm/paravirt.h:766
  invoke_softirq kernel/softirq.c:373 [inline]
  irq_exit+0x227/0x230 kernel/softirq.c:413
  exiting_irq arch/x86/include/asm/apic.h:536 [inline]
  smp_apic_timer_interrupt+0x113/0x280 arch/x86/kernel/apic/apic.c:1137
  apic_timer_interrupt+0xf/0x20 arch/x86/entry/entry_64.S:830
  </IRQ>
RIP: 0010:arch_local_irq_restore arch/x86/include/asm/paravirt.h:756  
[inline]
RIP: 0010:console_unlock+0xe35/0xef0 kernel/printk/printk.c:2477
Code: 20 00 74 0c 48 c7 c7 f0 91 8a 88 e8 65 da 4f 00 48 83 3d ad fd 2d 07  
00 0f 84 b1 00 00 00 e8 d2 9c 16 00 48 8b 7c 24 10 57 9d <0f> 1f 44 00 00  
eb 91 e8 bf 9c 16 00 eb 8a e8 b8 9c 16 00 eb 83 48
RSP: 0018:ffff888092daf930 EFLAGS: 00000282 ORIG_RAX: ffffffffffffff13
RAX: ffffffff815c944e RBX: 0000000000000200 RCX: ffff888094422640
RDX: 0000000000000000 RSI: ffffffff815c8129 RDI: 0000000000000282
RBP: ffff888092daf9f0 R08: ffff888094422640 R09: fffffbfff111a4f1
R10: fffffbfff111a4f1 R11: 0000000000000000 R12: dffffc0000000000
R13: 0000000000000000 R14: 0000000000000001 R15: ffffffff88a3d748
  vprintk_emit+0x239/0x3a0 kernel/printk/printk.c:1996
  vprintk_default+0x28/0x30 kernel/printk/printk.c:2023
  vprintk_func+0x158/0x170 kernel/printk/printk_safe.c:386
  printk+0x62/0x8d kernel/printk/printk.c:2056
  __ntfs_error+0x185/0x190 fs/ntfs/debug.c:89
  read_ntfs_boot_sector fs/ntfs/super.c:675 [inline]
  ntfs_fill_super+0x720/0x2a40 fs/ntfs/super.c:2784
  mount_bdev+0x27c/0x390 fs/super.c:1415
  ntfs_mount+0x34/0x40 fs/ntfs/super.c:3051
  legacy_get_tree+0xf9/0x1a0 fs/fs_context.c:647
  vfs_get_tree+0x8b/0x2a0 fs/super.c:1545
  do_new_mount fs/namespace.c:2823 [inline]
  do_mount+0x16c0/0x2510 fs/namespace.c:3143
  ksys_mount+0xcc/0x100 fs/namespace.c:3352
  __do_sys_mount fs/namespace.c:3366 [inline]
  __se_sys_mount fs/namespace.c:3363 [inline]
  __x64_sys_mount+0xbf/0xd0 fs/namespace.c:3363
  do_syscall_64+0xf7/0x1c0 arch/x86/entry/common.c:290
  entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x441e99
Code: e8 fc ad 02 00 48 83 c4 18 c3 0f 1f 80 00 00 00 00 48 89 f8 48 89 f7  
48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff  
ff 0f 83 3b 0a fc ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007fff8d7174e8 EFLAGS: 00000246 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 0000000000441e99
RDX: 0000000020000140 RSI: 0000000020000280 RDI: 00000000200004c0
RBP: 000000000000f000 R08: 0000000000000000 R09: 00007fff8d717698
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000006ccdc8
R13: 00000000006cd440 R14: 0000000000000000 R15: 0000000000000000


^ permalink raw reply	[flat|nested] 5+ messages in thread
* Re: WARNING: bad unlock balance in rcu_lock_release
  2019-10-13 21:28 ` syzbot
@ 2019-10-15  7:56   ` Jan Kara
  2019-10-17  5:27     ` Eric Biggers
  0 siblings, 1 reply; 5+ messages in thread
From: Jan Kara @ 2019-10-15  7:56 UTC (permalink / raw)
  To: syzbot; +Cc: linux-fsdevel, linux-kernel, syzkaller-bugs, viro

On Sun 13-10-19 14:28:06, syzbot wrote:
> syzbot has found a reproducer for the following crash on:
> 
> HEAD commit:    da940012 Merge tag 'char-misc-5.4-rc3' of git://git.kernel..
> git tree:       upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=12cfdf4f600000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=2d2fd92a28d3e50
> dashboard link: https://syzkaller.appspot.com/bug?extid=f9545ab3e9f85cd43a3a
> compiler:       clang version 9.0.0 (/home/glider/llvm/clang
> 80fee25776c2fb61e74c1ecb1a523375c2500b69)
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=148c9fc7600000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=100d3f8b600000
> 
> IMPORTANT: if you fix the bug, please add the following tag to the commit:
> Reported-by: syzbot+f9545ab3e9f85cd43a3a@syzkaller.appspotmail.com
> 
> =====================================
> WARNING: bad unlock balance detected!
> 5.4.0-rc2+ #0 Not tainted
> -------------------------------------
> syz-executor111/7877 is trying to release lock (rcu_callback) at:
> [<ffffffff81612bd4>] rcu_lock_release+0x4/0x20 include/linux/rcupdate.h:212
> but there are no more locks to release!

Hum, this is really weird. Look:

> other info that might help us debug this:
> 1 lock held by syz-executor111/7877:
>  #0: ffff8880a3c600d8 (&type->s_umount_key#42/1){+.+.}, at:
> alloc_super+0x15f/0x790 fs/super.c:229
> 
> stack backtrace:
> CPU: 1 PID: 7877 Comm: syz-executor111 Not tainted 5.4.0-rc2+ #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
> Google 01/01/2011
> Call Trace:
>  <IRQ>
>  __dump_stack lib/dump_stack.c:77 [inline]
>  dump_stack+0x1d8/0x2f8 lib/dump_stack.c:113
>  print_unlock_imbalance_bug+0x20b/0x240 kernel/locking/lockdep.c:4008
>  __lock_release kernel/locking/lockdep.c:4244 [inline]
>  lock_release+0x473/0x780 kernel/locking/lockdep.c:4506
>  rcu_lock_release+0x1c/0x20 include/linux/rcupdate.h:214
>  __rcu_reclaim kernel/rcu/rcu.h:223 [inline]

__rcu_reclaim_kernel() has:

        rcu_lock_acquire(&rcu_callback_map);
        if (__is_kfree_rcu_offset(offset)) {
                trace_rcu_invoke_kfree_callback(rn, head, offset);
                kfree((void *)head - offset);
                rcu_lock_release(&rcu_callback_map);
                return true;
        } else {
                trace_rcu_invoke_callback(rn, head);
                f = head->func;
                WRITE_ONCE(head->func, (rcu_callback_t)0L);
                f(head);
                rcu_lock_release(&rcu_callback_map);
                return false;
        }

So RCU locking is clearly balanced there. The only possibility I can see
how this can happen is that RCU callback we have called actually released
rcu_callback_map but grepping the kernel doesn't show any other place where
that would get released? Confused.

But apparently there is even a reproducer for this so we could dig
further...

								Honza

>  rcu_do_batch kernel/rcu/tree.c:2157 [inline]
>  rcu_core+0x84f/0x1050 kernel/rcu/tree.c:2377
>  rcu_core_si+0x9/0x10 kernel/rcu/tree.c:2386
>  __do_softirq+0x333/0x7c4 arch/x86/include/asm/paravirt.h:766
>  invoke_softirq kernel/softirq.c:373 [inline]
>  irq_exit+0x227/0x230 kernel/softirq.c:413
>  exiting_irq arch/x86/include/asm/apic.h:536 [inline]
>  smp_apic_timer_interrupt+0x113/0x280 arch/x86/kernel/apic/apic.c:1137
>  apic_timer_interrupt+0xf/0x20 arch/x86/entry/entry_64.S:830
>  </IRQ>
> RIP: 0010:arch_local_irq_restore arch/x86/include/asm/paravirt.h:756
> [inline]
> RIP: 0010:console_unlock+0xe35/0xef0 kernel/printk/printk.c:2477
> Code: 20 00 74 0c 48 c7 c7 f0 91 8a 88 e8 65 da 4f 00 48 83 3d ad fd 2d 07
> 00 0f 84 b1 00 00 00 e8 d2 9c 16 00 48 8b 7c 24 10 57 9d <0f> 1f 44 00 00 eb
> 91 e8 bf 9c 16 00 eb 8a e8 b8 9c 16 00 eb 83 48
> RSP: 0018:ffff888092daf930 EFLAGS: 00000282 ORIG_RAX: ffffffffffffff13
> RAX: ffffffff815c944e RBX: 0000000000000200 RCX: ffff888094422640
> RDX: 0000000000000000 RSI: ffffffff815c8129 RDI: 0000000000000282
> RBP: ffff888092daf9f0 R08: ffff888094422640 R09: fffffbfff111a4f1
> R10: fffffbfff111a4f1 R11: 0000000000000000 R12: dffffc0000000000
> R13: 0000000000000000 R14: 0000000000000001 R15: ffffffff88a3d748
>  vprintk_emit+0x239/0x3a0 kernel/printk/printk.c:1996
>  vprintk_default+0x28/0x30 kernel/printk/printk.c:2023
>  vprintk_func+0x158/0x170 kernel/printk/printk_safe.c:386
>  printk+0x62/0x8d kernel/printk/printk.c:2056
>  __ntfs_error+0x185/0x190 fs/ntfs/debug.c:89
>  read_ntfs_boot_sector fs/ntfs/super.c:675 [inline]
>  ntfs_fill_super+0x720/0x2a40 fs/ntfs/super.c:2784
>  mount_bdev+0x27c/0x390 fs/super.c:1415
>  ntfs_mount+0x34/0x40 fs/ntfs/super.c:3051
>  legacy_get_tree+0xf9/0x1a0 fs/fs_context.c:647
>  vfs_get_tree+0x8b/0x2a0 fs/super.c:1545
>  do_new_mount fs/namespace.c:2823 [inline]
>  do_mount+0x16c0/0x2510 fs/namespace.c:3143
>  ksys_mount+0xcc/0x100 fs/namespace.c:3352
>  __do_sys_mount fs/namespace.c:3366 [inline]
>  __se_sys_mount fs/namespace.c:3363 [inline]
>  __x64_sys_mount+0xbf/0xd0 fs/namespace.c:3363
>  do_syscall_64+0xf7/0x1c0 arch/x86/entry/common.c:290
>  entry_SYSCALL_64_after_hwframe+0x49/0xbe
> RIP: 0033:0x441e99
> Code: e8 fc ad 02 00 48 83 c4 18 c3 0f 1f 80 00 00 00 00 48 89 f8 48 89 f7
> 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff
> 0f 83 3b 0a fc ff c3 66 2e 0f 1f 84 00 00 00 00
> RSP: 002b:00007fff8d7174e8 EFLAGS: 00000246 ORIG_RAX: 00000000000000a5
> RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 0000000000441e99
> RDX: 0000000020000140 RSI: 0000000020000280 RDI: 00000000200004c0
> RBP: 000000000000f000 R08: 0000000000000000 R09: 00007fff8d717698
> R10: 0000000000000000 R11: 0000000000000246 R12: 00000000006ccdc8
> R13: 00000000006cd440 R14: 0000000000000000 R15: 0000000000000000
> 
-- 
Jan Kara <jack@suse.com>
SUSE Labs, CR

^ permalink raw reply	[flat|nested] 5+ messages in thread
* Re: WARNING: bad unlock balance in rcu_lock_release
  2019-10-15  7:56   ` Jan Kara
@ 2019-10-17  5:27     ` Eric Biggers
  0 siblings, 0 replies; 5+ messages in thread
From: Eric Biggers @ 2019-10-17  5:27 UTC (permalink / raw)
  To: Jan Kara; +Cc: syzbot, linux-fsdevel, linux-kernel, syzkaller-bugs, viro

On Tue, Oct 15, 2019 at 09:56:31AM +0200, Jan Kara wrote:
> On Sun 13-10-19 14:28:06, syzbot wrote:
> > syzbot has found a reproducer for the following crash on:
> > 
> > HEAD commit:    da940012 Merge tag 'char-misc-5.4-rc3' of git://git.kernel..
> > git tree:       upstream
> > console output: https://syzkaller.appspot.com/x/log.txt?x=12cfdf4f600000
> > kernel config:  https://syzkaller.appspot.com/x/.config?x=2d2fd92a28d3e50
> > dashboard link: https://syzkaller.appspot.com/bug?extid=f9545ab3e9f85cd43a3a
> > compiler:       clang version 9.0.0 (/home/glider/llvm/clang
> > 80fee25776c2fb61e74c1ecb1a523375c2500b69)
> > syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=148c9fc7600000
> > C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=100d3f8b600000
> > 
> > IMPORTANT: if you fix the bug, please add the following tag to the commit:
> > Reported-by: syzbot+f9545ab3e9f85cd43a3a@syzkaller.appspotmail.com
> > 
> > =====================================
> > WARNING: bad unlock balance detected!
> > 5.4.0-rc2+ #0 Not tainted
> > -------------------------------------
> > syz-executor111/7877 is trying to release lock (rcu_callback) at:
> > [<ffffffff81612bd4>] rcu_lock_release+0x4/0x20 include/linux/rcupdate.h:212
> > but there are no more locks to release!
> 
> Hum, this is really weird. Look:
> 
> > other info that might help us debug this:
> > 1 lock held by syz-executor111/7877:
> >  #0: ffff8880a3c600d8 (&type->s_umount_key#42/1){+.+.}, at:
> > alloc_super+0x15f/0x790 fs/super.c:229
> > 
> > stack backtrace:
> > CPU: 1 PID: 7877 Comm: syz-executor111 Not tainted 5.4.0-rc2+ #0
> > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
> > Google 01/01/2011
> > Call Trace:
> >  <IRQ>
> >  __dump_stack lib/dump_stack.c:77 [inline]
> >  dump_stack+0x1d8/0x2f8 lib/dump_stack.c:113
> >  print_unlock_imbalance_bug+0x20b/0x240 kernel/locking/lockdep.c:4008
> >  __lock_release kernel/locking/lockdep.c:4244 [inline]
> >  lock_release+0x473/0x780 kernel/locking/lockdep.c:4506
> >  rcu_lock_release+0x1c/0x20 include/linux/rcupdate.h:214
> >  __rcu_reclaim kernel/rcu/rcu.h:223 [inline]
> 
> __rcu_reclaim_kernel() has:
> 
>         rcu_lock_acquire(&rcu_callback_map);
>         if (__is_kfree_rcu_offset(offset)) {
>                 trace_rcu_invoke_kfree_callback(rn, head, offset);
>                 kfree((void *)head - offset);
>                 rcu_lock_release(&rcu_callback_map);
>                 return true;
>         } else {
>                 trace_rcu_invoke_callback(rn, head);
>                 f = head->func;
>                 WRITE_ONCE(head->func, (rcu_callback_t)0L);
>                 f(head);
>                 rcu_lock_release(&rcu_callback_map);
>                 return false;
>         }
> 
> So RCU locking is clearly balanced there. The only possibility I can see
> how this can happen is that RCU callback we have called actually released
> rcu_callback_map but grepping the kernel doesn't show any other place where
> that would get released? Confused.
> 
> But apparently there is even a reproducer for this so we could dig
> further...
> 

It's probably the same cause as "WARNING: bad unlock balance in rcu_core", see
the thread: https://lkml.kernel.org/linux-fsdevel/000000000000c0bffa0586795098@google.com/T/#u
Looks related to the lockdep_off() in ntfs_fill_super().

- Eric

^ permalink raw reply	[flat|nested] 5+ messages in thread
* Re: WARNING: bad unlock balance in rcu_lock_release
  2019-06-23 12:37 WARNING: bad unlock balance in rcu_lock_release syzbot
  2019-10-13 21:28 ` syzbot
@ 2020-04-30  6:15 ` syzbot
  1 sibling, 0 replies; 5+ messages in thread
From: syzbot @ 2020-04-30  6:15 UTC (permalink / raw)
  To: ebiggers, jack, linux-fsdevel, linux-kernel, mingo, peterz,
	syzkaller-bugs, viro, will

syzbot suspects this bug was fixed by commit:

commit 10476e6304222ced7df9b3d5fb0a043b3c2a1ad8
Author: Peter Zijlstra <peterz@infradead.org>
Date:   Fri Mar 13 08:56:38 2020 +0000

    locking/lockdep: Fix bad recursion pattern

bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=16d64bac100000
start commit:   7d194c21 Linux 5.4-rc4
git tree:       upstream
kernel config:  https://syzkaller.appspot.com/x/.config?x=6c03e4d33fa96d51
dashboard link: https://syzkaller.appspot.com/bug?extid=f9545ab3e9f85cd43a3a
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=10a0a8c0e00000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=13dd2dd8e00000

If the result looks correct, please mark the bug fixed by replying with:

#syz fix: locking/lockdep: Fix bad recursion pattern

For information about bisection process see: https://goo.gl/tpsmEJ#bisection

^ permalink raw reply	[flat|nested] 5+ messages in thread
end of thread, other threads:[~2020-04-30  6:15 UTC | newest]

Thread overview: 5+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2019-06-23 12:37 WARNING: bad unlock balance in rcu_lock_release syzbot
2019-10-13 21:28 ` syzbot
2019-10-15  7:56   ` Jan Kara
2019-10-17  5:27     ` Eric Biggers
2020-04-30  6:15 ` syzbot

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