Re: WARNING: bad unlock balance in ucma_event_handler

[Eric Biggers]

On Wed, Jun 13, 2018 at 11:05:43AM -0600, Jason Gunthorpe wrote:
> On Wed, Jun 13, 2018 at 06:47:02AM -0700, syzbot wrote:
> > Hello,
> > 
> > syzbot found the following crash on:
> > 
> > HEAD commit:    73fcb1a370c7 Merge branch 'akpm' (patches from Andrew)
> > git tree:       upstream
> > console output: https://syzkaller.appspot.com/x/log.txt?x=16d70827800000
> > kernel config:  https://syzkaller.appspot.com/x/.config?x=f3b4e30da84ec1ed
> > dashboard link: https://syzkaller.appspot.com/bug?extid=e5579222b6a3edd96522
> > compiler:       gcc (GCC) 8.0.1 20180413 (experimental)
> > syzkaller repro:https://syzkaller.appspot.com/x/repro.syz?x=176daf97800000
> > C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=15e7bd57800000
> > 
> > IMPORTANT: if you fix the bug, please add the following tag to the commit:
> > Reported-by: syzbot+e5579222b6a3edd96522@xxxxxxxxxxxxxxxxxxxxxxxxx
> > 
> > 
> > =====================================
> > WARNING: bad unlock balance detected!
> > 4.17.0-rc5+ #58 Not tainted
> > kworker/u4:0/6 is trying to release lock (&file->mut) at:
> > [<ffffffff8593ecc0>] ucma_event_handler+0x780/0xff0
> > drivers/infiniband/core/ucma.c:390
> > but there are no more locks to release!
> > 
> > other info that might help us debug this:
> > 4 locks held by kworker/u4:0/6:
> >  #0:         (ptrval) ((wq_completion)"ib_addr"){+.+.}, at:
> > __write_once_size include/linux/compiler.h:215 [inline]
> >  #0:         (ptrval) ((wq_completion)"ib_addr"){+.+.}, at:
> > arch_atomic64_set arch/x86/include/asm/atomic64_64.h:34 [inline]
> >  #0:         (ptrval) ((wq_completion)"ib_addr"){+.+.}, at: atomic64_set
> > include/asm-generic/atomic-instrumented.h:40 [inline]
> >  #0:         (ptrval) ((wq_completion)"ib_addr"){+.+.}, at: atomic_long_set
> > include/asm-generic/atomic-long.h:57 [inline]
> >  #0:         (ptrval) ((wq_completion)"ib_addr"){+.+.}, at: set_work_data
> > kernel/workqueue.c:617 [inline]
> >  #0:         (ptrval) ((wq_completion)"ib_addr"){+.+.}, at:
> > set_work_pool_and_clear_pending kernel/workqueue.c:644 [inline]
> >  #0:         (ptrval) ((wq_completion)"ib_addr"){+.+.}, at:
> > process_one_work+0xaef/0x1b50 kernel/workqueue.c:2116
> >  #1:         (ptrval) ((work_completion)(&(&req->work)->work)){+.+.}, at:
> > process_one_work+0xb46/0x1b50 kernel/workqueue.c:2120
> >  #2:         (ptrval) (&id_priv->handler_mutex){+.+.}, at:
> > addr_handler+0xa6/0x3d0 drivers/infiniband/core/cma.c:2796
> >  #3:         (ptrval) (&file->mut){+.+.}, at: ucma_event_handler+0x10e/0xff0
> > drivers/infiniband/core/ucma.c:350
> 
> I think this is probably a use-after-free race, eg when we do
> ctx->file->mut we have raced with ucma_free_ctx() ..
> 
> Which probably means something along the way to free_ctx() did not
> call rdma_addr_cancel?
> 
> Jason

This is still happening.  Just FYI, ignoring these reports doesn't make the bugs
go away.  Here's a crash report from v5.2.0-rc4:

https://syzkaller.appspot.com/text?tag=CrashReport&x=102aa7c1a00000

=====================================
WARNING: bad unlock balance detected!
5.2.0-rc4 #44 Not tainted
-------------------------------------
kworker/u4:2/61 is trying to release lock (&file->mut) at:
[<ffffffff851a3f81>] ucma_event_handler+0x711/0xef0 drivers/infiniband/core/ucma.c:394
but there are no more locks to release!

other info that might help us debug this:
4 locks held by kworker/u4:2/61:
 #0: 000000005ff5546b ((wq_completion)ib_addr){+.+.}, at: __write_once_size include/linux/compiler.h:221 [inline]
 #0: 000000005ff5546b ((wq_completion)ib_addr){+.+.}, at: arch_atomic64_set arch/x86/include/asm/atomic64_64.h:34 [inline]
 #0: 000000005ff5546b ((wq_completion)ib_addr){+.+.}, at: atomic64_set include/asm-generic/atomic-instrumented.h:855 [inline]
 #0: 000000005ff5546b ((wq_completion)ib_addr){+.+.}, at: atomic_long_set include/asm-generic/atomic-long.h:40 [inline]
 #0: 000000005ff5546b ((wq_completion)ib_addr){+.+.}, at: set_work_data kernel/workqueue.c:620 [inline]
 #0: 000000005ff5546b ((wq_completion)ib_addr){+.+.}, at: set_work_pool_and_clear_pending kernel/workqueue.c:647 [inline]
 #0: 000000005ff5546b ((wq_completion)ib_addr){+.+.}, at: process_one_work+0x87e/0x1790 kernel/workqueue.c:2240
 #1: 00000000d75dabcd ((work_completion)(&(&req->work)->work)){+.+.}, at: process_one_work+0x8b4/0x1790 kernel/workqueue.c:2244
 #2: 0000000058b7aa49 (&id_priv->handler_mutex){+.+.}, at: addr_handler+0xaf/0x3d0 drivers/infiniband/core/cma.c:3031
 #3: 00000000e5042b0a (&file->mut){+.+.}, at: ucma_event_handler+0xb3/0xef0 drivers/infiniband/core/ucma.c:354

stack backtrace:
CPU: 1 PID: 61 Comm: kworker/u4:2 Not tainted 5.2.0-rc4 #44
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Workqueue: ib_addr process_one_req
Call Trace:
 __dump_stack lib/dump_stack.c:77 [inline]
 dump_stack+0x172/0x1f0 lib/dump_stack.c:113
 print_unlock_imbalance_bug kernel/locking/lockdep.c:3846 [inline]
 print_unlock_imbalance_bug.cold+0x114/0x123 kernel/locking/lockdep.c:3823
 __lock_release kernel/locking/lockdep.c:4062 [inline]
 lock_release+0x67b/0xa00 kernel/locking/lockdep.c:4322
 __mutex_unlock_slowpath+0x8e/0x6b0 kernel/locking/mutex.c:1198
 mutex_unlock+0xd/0x10 kernel/locking/mutex.c:714
 ucma_event_handler+0x711/0xef0 drivers/infiniband/core/ucma.c:394
 addr_handler+0x2e9/0x3d0 drivers/infiniband/core/cma.c:3064
 process_one_req+0x106/0x680 drivers/infiniband/core/addr.c:644
 process_one_work+0x989/0x1790 kernel/workqueue.c:2269
 worker_thread+0x98/0xe40 kernel/workqueue.c:2415
 kthread+0x354/0x420 kernel/kthread.c:255
 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:352

- Eric