On Fri, Apr 26, 2013 at 8:22 PM, Tejun Heo [off-list ref] wrote:

On Fri, Apr 26, 2013 at 07:40:20PM +0200, Sedat Dilek wrote:

quoted

Oops, NULL-pointer-deref [ __queue_work() ]

[   25.974932] BUG: unable to handle kernel NULL pointer dereference
at 0000000000000100
[   25.974944] IP: [<ffffffff81077502>] __queue_work+0x32/0x3d0

So, 0x100 deref near the top of the function.

...

quoted

[   25.975037] RIP: 0010:[<ffffffff81077502>]  [<ffffffff81077502>]
__queue_work+0x32/0x3d0
[   25.975047] RSP: 0018:ffff88008fed5c48  EFLAGS: 00010046
[   25.975052] RAX: 0000000000000096 RBX: 0000000000000292 RCX: 0000000000000000
[   25.975058] RDX: ffff880095281850 RSI: 0000000000000000 RDI: 0000000000000100
[   25.975063] RBP: ffff88008fed5c88 R08: 0000000000000000 R09: 0000000000000300
[   25.975069] R10: ffff880094981a00 R11: 0000000000000000 R12: ffff880095281850
[   25.975074] R13: 0000000000000000 R14: 0000000000000100 R15: 00000000000009c4
[   25.975081] FS:  00007f2f61707740(0000) GS:ffff88011fac0000(0000)
knlGS:0000000000000000
[   25.975088] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[   25.975093] CR2: 0000000000000100 CR3: 000000009101f000 CR4: 00000000000407e0
[   25.975099] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[   25.975104] DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400

...

quoted

[   25.975143] Call Trace:
[   25.975151]  [<ffffffff81077be5>] queue_work_on+0x45/0x50
[   25.975165]  [<ffffffffa016e8ff>] hci_req_run+0xbf/0xf0 [bluetooth]
[   25.975188]  [<ffffffffa016ea06>] __hci_req_sync+0xd6/0x1c0 [bluetooth]
[   25.975217]  [<ffffffffa016fad5>] hci_dev_open+0x275/0x2e0 [bluetooth]
[   25.975230]  [<ffffffffa0182752>] hci_sock_ioctl+0x1f2/0x3f0 [bluetooth]
[   25.975238]  [<ffffffff815c6050>] sock_do_ioctl+0x30/0x70
[   25.975245]  [<ffffffff815c75f9>] sock_ioctl+0x79/0x2f0
[   25.975254]  [<ffffffff811a8046>] do_vfs_ioctl+0x96/0x560
[   25.975262]  [<ffffffff811a85a1>] SyS_ioctl+0x91/0xb0
[   25.975271]  [<ffffffff816d989d>] system_call_fastpath+0x1a/0x1f
[   25.975276] Code: 89 e5 41 57 41 56 41 89 fe 41 55 49 89 f5 41 54
49 89 d4 53 48 83 ec 18 89 7d c8 9c 58 66 66 90 66 90 f6 c4 02 0f 85
56 02 00 00 <41> 8b 85 00 01 00 00 a9 00 00 01 00 0f 85 b0 02 00 00 48
c7 c2

All code
========
   0:   89 e5                   mov    %esp,%ebp
   2:   41 57                   push   %r15
   4:   41 56                   push   %r14
   6:   41 89 fe                mov    %edi,%r14d
   9:   41 55                   push   %r13
   b:   49 89 f5                mov    %rsi,%r13
   e:   41 54                   push   %r12
  10:   49 89 d4                mov    %rdx,%r12
  13:   53                      push   %rbx
  14:   48 83 ec 18             sub    $0x18,%rsp
  18:   89 7d c8                mov    %edi,-0x38(%rbp)
  1b:   9c                      pushfq
  1c:   58                      pop    %rax
  1d:   66 66 90                data32 xchg %ax,%ax
  20:   66 90                   xchg   %ax,%ax
  22:   f6 c4 02                test   $0x2,%ah
  25:   0f 85 56 02 00 00       jne    0x281
  2b:*  41 8b 85 00 01 00 00    mov    0x100(%r13),%eax     <-- trapping instruction
  32:   a9 00 00 01 00          test   $0x10000,%eax
  37:   0f 85 b0 02 00 00       jne    0x2ed
  3d:   48                      rex.W
  3e:   c7                      .byte 0xc7
  3f:   c2                      .byte 0xc2

The second argument %rsi is zero, which got transferred to %r13 and
then offset deref on it trapped.

The second argument is @wq and the oopsing code is the wq->flags deref
in the following if condition.

        /* if dying, only works from the same workqueue are allowed */
        if (unlikely(wq->flags & __WQ_DRAINING) &&
                WARN_ON_ONCE(!is_chained_work(wq)))
                return;

So, umm, don't pass in NULL as @wq. :)

Do you have a patch for this?

- Sedat -

--
tejun