Re: possible deadlock in perf_event_detach_bpf_prog

2018-04-08 Thread Y Song 
On Thu, Mar 29, 2018 at 2:18 PM, Daniel Borkmann  wrote:
> On 03/29/2018 11:04 PM, syzbot wrote:
>> Hello,
>>
>> syzbot hit the following crash on upstream commit
>> 3eb2ce825ea1ad89d20f7a3b5780df850e4be274 (Sun Mar 25 22:44:30 2018 +)
>> Linux 4.16-rc7
>> syzbot dashboard link: 
>> https://syzkaller.appspot.com/bug?extid=dc5ca0e4c9bfafaf2bae
>>
>> Unfortunately, I don't have any reproducer for this crash yet.
>> Raw console output: 
>> https://syzkaller.appspot.com/x/log.txt?id=4742532743299072
>> Kernel config: 
>> https://syzkaller.appspot.com/x/.config?id=-8440362230543204781
>> compiler: gcc (GCC) 7.1.1 20170620
>>
>> IMPORTANT: if you fix the bug, please add the following tag to the commit:
>> Reported-by: syzbot+dc5ca0e4c9bfafaf2...@syzkaller.appspotmail.com
>> It will help syzbot understand when the bug is fixed. See footer for details.
>> If you forward the report, please keep this part and the footer.
>>
>>
>> ==
>> WARNING: possible circular locking dependency detected
>> 4.16.0-rc7+ #3 Not tainted
>> --
>> syz-executor7/24531 is trying to acquire lock:
>>  (bpf_event_mutex){+.+.}, at: [<8a849b07>] 
>> perf_event_detach_bpf_prog+0x92/0x3d0 kernel/trace/bpf_trace.c:854
>>
>> but task is already holding lock:
>>  (>mmap_sem){}, at: [<38768f87>] vm_mmap_pgoff+0x198/0x280 
>> mm/util.c:353
>>
>> which lock already depends on the new lock.
>>
>>
>> the existing dependency chain (in reverse order) is:
>>
>> -> #1 (>mmap_sem){}:
>>__might_fault+0x13a/0x1d0 mm/memory.c:4571
>>_copy_to_user+0x2c/0xc0 lib/usercopy.c:25
>>copy_to_user include/linux/uaccess.h:155 [inline]
>>bpf_prog_array_copy_info+0xf2/0x1c0 kernel/bpf/core.c:1694
>>perf_event_query_prog_array+0x1c7/0x2c0 kernel/trace/bpf_trace.c:891
>
> Looks like we should move the two copy_to_user() outside of
> bpf_event_mutex section to avoid the deadlock.

This is introduced by one of my previous patches. The above suggested fix
makes sense. I will craft a patch and send to the mailing list for bpf branch
soon.

>
>>_perf_ioctl kernel/events/core.c:4750 [inline]
>>perf_ioctl+0x3e1/0x1480 kernel/events/core.c:4770
>>vfs_ioctl fs/ioctl.c:46 [inline]
>>do_vfs_ioctl+0x1b1/0x1520 fs/ioctl.c:686
>>SYSC_ioctl fs/ioctl.c:701 [inline]
>>SyS_ioctl+0x8f/0xc0 fs/ioctl.c:692
>>do_syscall_64+0x281/0x940 arch/x86/entry/common.c:287
>>entry_SYSCALL_64_after_hwframe+0x42/0xb7
>>
>> -> #0 (bpf_event_mutex){+.+.}:
>>lock_acquire+0x1d5/0x580 kernel/locking/lockdep.c:3920
>>__mutex_lock_common kernel/locking/mutex.c:756 [inline]
>>__mutex_lock+0x16f/0x1a80 kernel/locking/mutex.c:893
>>mutex_lock_nested+0x16/0x20 kernel/locking/mutex.c:908
>>perf_event_detach_bpf_prog+0x92/0x3d0 kernel/trace/bpf_trace.c:854
>>perf_event_free_bpf_prog kernel/events/core.c:8147 [inline]
>>_free_event+0xbdb/0x10f0 kernel/events/core.c:4116
>>put_event+0x24/0x30 kernel/events/core.c:4204
>>perf_mmap_close+0x60d/0x1010 kernel/events/core.c:5172
>>remove_vma+0xb4/0x1b0 mm/mmap.c:172
>>remove_vma_list mm/mmap.c:2490 [inline]
>>do_munmap+0x82a/0xdf0 mm/mmap.c:2731
>>mmap_region+0x59e/0x15a0 mm/mmap.c:1646
>>do_mmap+0x6c0/0xe00 mm/mmap.c:1483
>>do_mmap_pgoff include/linux/mm.h:2223 [inline]
>>vm_mmap_pgoff+0x1de/0x280 mm/util.c:355
>>SYSC_mmap_pgoff mm/mmap.c:1533 [inline]
>>SyS_mmap_pgoff+0x462/0x5f0 mm/mmap.c:1491
>>SYSC_mmap arch/x86/kernel/sys_x86_64.c:100 [inline]
>>SyS_mmap+0x16/0x20 arch/x86/kernel/sys_x86_64.c:91
>>do_syscall_64+0x281/0x940 arch/x86/entry/common.c:287
>>entry_SYSCALL_64_after_hwframe+0x42/0xb7
>>
>> other info that might help us debug this:
>>
>>  Possible unsafe locking scenario:
>>
>>CPU0CPU1
>>
>>   lock(>mmap_sem);
>>lock(bpf_event_mutex);
>>lock(>mmap_sem);
>>   lock(bpf_event_mutex);
>>
>>  *** DEADLOCK ***
>>
>> 1 lock held by syz-executor7/24531:
>>  #0:  (>mmap_sem){}, at: [<38768f87>] 
>> vm_mmap_pgoff+0x198/0x280 mm/util.c:353
>>
>> stack backtrace:
>> CPU: 0 PID: 24531 Comm: syz-executor7 Not tainted 4.16.0-rc7+ #3
>> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS 
>> Google 01/01/2011
>> Call Trace:
>>  __dump_stack lib/dump_stack.c:17 [inline]
>>  dump_stack+0x194/0x24d lib/dump_stack.c:53
>>  print_circular_bug.isra.38+0x2cd/0x2dc kernel/locking/lockdep.c:1223
>>  check_prev_add kernel/locking/lockdep.c:1863 [inline]
>>  check_prevs_add kernel/locking/lockdep.c:1976 [inline]
>>  validate_chain kernel/locking/lockdep.c:2417 [inline]
>>  __lock_acquire+0x30a8/0x3e00

Re: possible deadlock in perf_event_detach_bpf_prog

2018-03-29 Thread Daniel Borkmann 
On 03/29/2018 11:04 PM, syzbot wrote:
> Hello,
> 
> syzbot hit the following crash on upstream commit
> 3eb2ce825ea1ad89d20f7a3b5780df850e4be274 (Sun Mar 25 22:44:30 2018 +)
> Linux 4.16-rc7
> syzbot dashboard link: 
> https://syzkaller.appspot.com/bug?extid=dc5ca0e4c9bfafaf2bae
> 
> Unfortunately, I don't have any reproducer for this crash yet.
> Raw console output: 
> https://syzkaller.appspot.com/x/log.txt?id=4742532743299072
> Kernel config: https://syzkaller.appspot.com/x/.config?id=-8440362230543204781
> compiler: gcc (GCC) 7.1.1 20170620
> 
> IMPORTANT: if you fix the bug, please add the following tag to the commit:
> Reported-by: syzbot+dc5ca0e4c9bfafaf2...@syzkaller.appspotmail.com
> It will help syzbot understand when the bug is fixed. See footer for details.
> If you forward the report, please keep this part and the footer.
> 
> 
> ==
> WARNING: possible circular locking dependency detected
> 4.16.0-rc7+ #3 Not tainted
> --
> syz-executor7/24531 is trying to acquire lock:
>  (bpf_event_mutex){+.+.}, at: [<8a849b07>] 
> perf_event_detach_bpf_prog+0x92/0x3d0 kernel/trace/bpf_trace.c:854
> 
> but task is already holding lock:
>  (>mmap_sem){}, at: [<38768f87>] vm_mmap_pgoff+0x198/0x280 
> mm/util.c:353
> 
> which lock already depends on the new lock.
> 
> 
> the existing dependency chain (in reverse order) is:
> 
> -> #1 (>mmap_sem){}:
>    __might_fault+0x13a/0x1d0 mm/memory.c:4571
>    _copy_to_user+0x2c/0xc0 lib/usercopy.c:25
>    copy_to_user include/linux/uaccess.h:155 [inline]
>    bpf_prog_array_copy_info+0xf2/0x1c0 kernel/bpf/core.c:1694
>    perf_event_query_prog_array+0x1c7/0x2c0 kernel/trace/bpf_trace.c:891

Looks like we should move the two copy_to_user() outside of
bpf_event_mutex section to avoid the deadlock.

>    _perf_ioctl kernel/events/core.c:4750 [inline]
>    perf_ioctl+0x3e1/0x1480 kernel/events/core.c:4770
>    vfs_ioctl fs/ioctl.c:46 [inline]
>    do_vfs_ioctl+0x1b1/0x1520 fs/ioctl.c:686
>    SYSC_ioctl fs/ioctl.c:701 [inline]
>    SyS_ioctl+0x8f/0xc0 fs/ioctl.c:692
>    do_syscall_64+0x281/0x940 arch/x86/entry/common.c:287
>    entry_SYSCALL_64_after_hwframe+0x42/0xb7
> 
> -> #0 (bpf_event_mutex){+.+.}:
>    lock_acquire+0x1d5/0x580 kernel/locking/lockdep.c:3920
>    __mutex_lock_common kernel/locking/mutex.c:756 [inline]
>    __mutex_lock+0x16f/0x1a80 kernel/locking/mutex.c:893
>    mutex_lock_nested+0x16/0x20 kernel/locking/mutex.c:908
>    perf_event_detach_bpf_prog+0x92/0x3d0 kernel/trace/bpf_trace.c:854
>    perf_event_free_bpf_prog kernel/events/core.c:8147 [inline]
>    _free_event+0xbdb/0x10f0 kernel/events/core.c:4116
>    put_event+0x24/0x30 kernel/events/core.c:4204
>    perf_mmap_close+0x60d/0x1010 kernel/events/core.c:5172
>    remove_vma+0xb4/0x1b0 mm/mmap.c:172
>    remove_vma_list mm/mmap.c:2490 [inline]
>    do_munmap+0x82a/0xdf0 mm/mmap.c:2731
>    mmap_region+0x59e/0x15a0 mm/mmap.c:1646
>    do_mmap+0x6c0/0xe00 mm/mmap.c:1483
>    do_mmap_pgoff include/linux/mm.h:2223 [inline]
>    vm_mmap_pgoff+0x1de/0x280 mm/util.c:355
>    SYSC_mmap_pgoff mm/mmap.c:1533 [inline]
>    SyS_mmap_pgoff+0x462/0x5f0 mm/mmap.c:1491
>    SYSC_mmap arch/x86/kernel/sys_x86_64.c:100 [inline]
>    SyS_mmap+0x16/0x20 arch/x86/kernel/sys_x86_64.c:91
>    do_syscall_64+0x281/0x940 arch/x86/entry/common.c:287
>    entry_SYSCALL_64_after_hwframe+0x42/0xb7
> 
> other info that might help us debug this:
> 
>  Possible unsafe locking scenario:
> 
>    CPU0    CPU1
>        
>   lock(>mmap_sem);
>    lock(bpf_event_mutex);
>    lock(>mmap_sem);
>   lock(bpf_event_mutex);
> 
>  *** DEADLOCK ***
> 
> 1 lock held by syz-executor7/24531:
>  #0:  (>mmap_sem){}, at: [<38768f87>] 
> vm_mmap_pgoff+0x198/0x280 mm/util.c:353
> 
> stack backtrace:
> CPU: 0 PID: 24531 Comm: syz-executor7 Not tainted 4.16.0-rc7+ #3
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS 
> Google 01/01/2011
> Call Trace:
>  __dump_stack lib/dump_stack.c:17 [inline]
>  dump_stack+0x194/0x24d lib/dump_stack.c:53
>  print_circular_bug.isra.38+0x2cd/0x2dc kernel/locking/lockdep.c:1223
>  check_prev_add kernel/locking/lockdep.c:1863 [inline]
>  check_prevs_add kernel/locking/lockdep.c:1976 [inline]
>  validate_chain kernel/locking/lockdep.c:2417 [inline]
>  __lock_acquire+0x30a8/0x3e00 kernel/locking/lockdep.c:3431
>  lock_acquire+0x1d5/0x580 kernel/locking/lockdep.c:3920
>  __mutex_lock_common kernel/locking/mutex.c:756 [inline]
>  __mutex_lock+0x16f/0x1a80 kernel/locking/mutex.c:893
>  mutex_lock_nested+0x16/0x20 kernel/locking/mutex.c:908
>  perf_event_detach_bpf_prog+0x92/0x3d0 kernel/trace/bpf_trace.c:854
>  

possible deadlock in perf_event_detach_bpf_prog

2018-03-29 Thread syzbot 

Hello,

syzbot hit the following crash on upstream commit
3eb2ce825ea1ad89d20f7a3b5780df850e4be274 (Sun Mar 25 22:44:30 2018 +)
Linux 4.16-rc7
syzbot dashboard link:  
https://syzkaller.appspot.com/bug?extid=dc5ca0e4c9bfafaf2bae


Unfortunately, I don't have any reproducer for this crash yet.
Raw console output:  
https://syzkaller.appspot.com/x/log.txt?id=4742532743299072
Kernel config:  
https://syzkaller.appspot.com/x/.config?id=-8440362230543204781

compiler: gcc (GCC) 7.1.1 20170620

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+dc5ca0e4c9bfafaf2...@syzkaller.appspotmail.com
It will help syzbot understand when the bug is fixed. See footer for  
details.

If you forward the report, please keep this part and the footer.


==
WARNING: possible circular locking dependency detected
4.16.0-rc7+ #3 Not tainted
--
syz-executor7/24531 is trying to acquire lock:
 (bpf_event_mutex){+.+.}, at: [<8a849b07>]  
perf_event_detach_bpf_prog+0x92/0x3d0 kernel/trace/bpf_trace.c:854


but task is already holding lock:
 (>mmap_sem){}, at: [<38768f87>] vm_mmap_pgoff+0x198/0x280  
mm/util.c:353


which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #1 (>mmap_sem){}:
   __might_fault+0x13a/0x1d0 mm/memory.c:4571
   _copy_to_user+0x2c/0xc0 lib/usercopy.c:25
   copy_to_user include/linux/uaccess.h:155 [inline]
   bpf_prog_array_copy_info+0xf2/0x1c0 kernel/bpf/core.c:1694
   perf_event_query_prog_array+0x1c7/0x2c0 kernel/trace/bpf_trace.c:891
   _perf_ioctl kernel/events/core.c:4750 [inline]
   perf_ioctl+0x3e1/0x1480 kernel/events/core.c:4770
   vfs_ioctl fs/ioctl.c:46 [inline]
   do_vfs_ioctl+0x1b1/0x1520 fs/ioctl.c:686
   SYSC_ioctl fs/ioctl.c:701 [inline]
   SyS_ioctl+0x8f/0xc0 fs/ioctl.c:692
   do_syscall_64+0x281/0x940 arch/x86/entry/common.c:287
   entry_SYSCALL_64_after_hwframe+0x42/0xb7

-> #0 (bpf_event_mutex){+.+.}:
   lock_acquire+0x1d5/0x580 kernel/locking/lockdep.c:3920
   __mutex_lock_common kernel/locking/mutex.c:756 [inline]
   __mutex_lock+0x16f/0x1a80 kernel/locking/mutex.c:893
   mutex_lock_nested+0x16/0x20 kernel/locking/mutex.c:908
   perf_event_detach_bpf_prog+0x92/0x3d0 kernel/trace/bpf_trace.c:854
   perf_event_free_bpf_prog kernel/events/core.c:8147 [inline]
   _free_event+0xbdb/0x10f0 kernel/events/core.c:4116
   put_event+0x24/0x30 kernel/events/core.c:4204
   perf_mmap_close+0x60d/0x1010 kernel/events/core.c:5172
   remove_vma+0xb4/0x1b0 mm/mmap.c:172
   remove_vma_list mm/mmap.c:2490 [inline]
   do_munmap+0x82a/0xdf0 mm/mmap.c:2731
   mmap_region+0x59e/0x15a0 mm/mmap.c:1646
   do_mmap+0x6c0/0xe00 mm/mmap.c:1483
   do_mmap_pgoff include/linux/mm.h:2223 [inline]
   vm_mmap_pgoff+0x1de/0x280 mm/util.c:355
   SYSC_mmap_pgoff mm/mmap.c:1533 [inline]
   SyS_mmap_pgoff+0x462/0x5f0 mm/mmap.c:1491
   SYSC_mmap arch/x86/kernel/sys_x86_64.c:100 [inline]
   SyS_mmap+0x16/0x20 arch/x86/kernel/sys_x86_64.c:91
   do_syscall_64+0x281/0x940 arch/x86/entry/common.c:287
   entry_SYSCALL_64_after_hwframe+0x42/0xb7

other info that might help us debug this:

 Possible unsafe locking scenario:

   CPU0CPU1
   
  lock(>mmap_sem);
   lock(bpf_event_mutex);
   lock(>mmap_sem);
  lock(bpf_event_mutex);

 *** DEADLOCK ***

1 lock held by syz-executor7/24531:
 #0:  (>mmap_sem){}, at: [<38768f87>]  
vm_mmap_pgoff+0x198/0x280 mm/util.c:353


stack backtrace:
CPU: 0 PID: 24531 Comm: syz-executor7 Not tainted 4.16.0-rc7+ #3
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS  
Google 01/01/2011

Call Trace:
 __dump_stack lib/dump_stack.c:17 [inline]
 dump_stack+0x194/0x24d lib/dump_stack.c:53
 print_circular_bug.isra.38+0x2cd/0x2dc kernel/locking/lockdep.c:1223
 check_prev_add kernel/locking/lockdep.c:1863 [inline]
 check_prevs_add kernel/locking/lockdep.c:1976 [inline]
 validate_chain kernel/locking/lockdep.c:2417 [inline]
 __lock_acquire+0x30a8/0x3e00 kernel/locking/lockdep.c:3431
 lock_acquire+0x1d5/0x580 kernel/locking/lockdep.c:3920
 __mutex_lock_common kernel/locking/mutex.c:756 [inline]
 __mutex_lock+0x16f/0x1a80 kernel/locking/mutex.c:893
 mutex_lock_nested+0x16/0x20 kernel/locking/mutex.c:908
 perf_event_detach_bpf_prog+0x92/0x3d0 kernel/trace/bpf_trace.c:854
 perf_event_free_bpf_prog kernel/events/core.c:8147 [inline]
 _free_event+0xbdb/0x10f0 kernel/events/core.c:4116
 put_event+0x24/0x30 kernel/events/core.c:4204
 perf_mmap_close+0x60d/0x1010 kernel/events/core.c:5172
 remove_vma+0xb4/0x1b0 mm/mmap.c:172
 remove_vma_list mm/mmap.c:2490 [inline]
 do_munmap+0x82a/0xdf0 mm/mmap.c:2731
 mmap_region+0x59e/0x15a0