Re: ptrace BUG [was: mmotm 2010-10-13-17-13 uploaded]

[Frederic Weisbecker]

On Wed, Oct 20, 2010 at 05:50:15PM +0200, Jiri Slaby wrote:
> On 10/14/2010 02:13 AM, akpm@xxxxxxxxxxxxxxxxxxxx wrote:
> > The mm-of-the-moment snapshot 2010-10-13-17-13 has been uploaded to
> 
> Hi, I tried to run a process in gdb and got this BUG:
> 
> BUG: unable to handle kernel NULL pointer dereference at 0000000000000080
> IP: [<ffffffff810c5c08>] fetch_bp_busy_slots.clone.1+0x28/0x1c0
> PGD 1bacfa067 PUD 13b7f1067 PMD 0
> Oops: 0000 [#1] SMP
> last sysfs file: /sys/devices/virtual/net/tun0/statistics/collisions
> CPU 1
> Modules linked in: dvb_usb_af9015 dvb_usb



Do you have this fix?

d580ff8699e8811a9af37e9de4dea375401bdeec
("perf, hw_breakpoint: Fix crash in hw_breakpoint creation")

It's in tip:/perf/core, which perhaps hasn't yet reached -next.


This should fix the problem.


> 
> Pid: 18934, comm: gdb Not tainted 2.6.36-rc7-mm1_64+ #1286 To be filled
> by O.E.M./To Be Filled By O.E.M.
> RIP: 0010:[<ffffffff810c5c08>]  [<ffffffff810c5c08>]
> fetch_bp_busy_slots.clone.1+0x28/0x1c0
> RSP: 0018:ffff8801b71a3ca8  EFLAGS: 00010286
> RAX: 0000000000000000 RBX: ffff8801b71a3d18 RCX: 0000000000000000
> RDX: ffff8801b71a3fd8 RSI: ffff88013bafc800 RDI: ffff8801b71a3d18
> RBP: ffff8801b71a3cf8 R08: ffffffff81039620 R09: ffff88013bafc800
> R10: fffe060673f40000 R11: 0000000000000001 R12: ffff88013bafc800
> R13: 0000000000000000 R14: 00000000ffffffff R15: ffff88013bafc800
> FS:  00007f0acb802700(0000) GS:ffff8800af280000(0000) knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 0000000000000080 CR3: 0000000188f40000 CR4: 00000000000006e0
> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
> Process gdb (pid: 18934, threadinfo ffff8801b71a2000, task ffff88019ddfee80)
> Stack:
>  0000000000000000 0000000000000000 0000000000000000 0000000000000000
> <0> 0000000000000000 ffff88013bafc800 ffff88013bafc800 0000000000000000
> <0> 0000000000000000 ffff88013bafc800 ffff8801b71a3d38 ffffffff810c5dfa
> Call Trace:
>  [<ffffffff810c5dfa>] __reserve_bp_slot+0x5a/0x90
>  [<ffffffff815c26d9>] ? mutex_lock+0x19/0x50
>  [<ffffffff810c5e60>] reserve_bp_slot+0x20/0x40
>  [<ffffffff810c5f41>] register_perf_hw_breakpoint+0x11/0x50
>  [<ffffffff810c8da2>] ? filemap_fault+0x122/0x4b0
>  [<ffffffff810c5fad>] hw_breakpoint_event_init+0x2d/0x50
>  [<ffffffff810c4346>] perf_init_event+0x36/0x80
>  [<ffffffff810c45d8>] perf_event_alloc+0x248/0x350
>  [<ffffffff81039620>] ? ptrace_triggered+0x0/0x40
>  [<ffffffff810c49bc>] perf_event_create_kernel_counter+0x2c/0x150
>  [<ffffffff810c5601>] register_user_hw_breakpoint+0x11/0x20
>  [<ffffffff8103975e>] ptrace_set_breakpoint_addr+0xde/0x100
>  [<ffffffff8103a485>] ptrace_set_debugreg+0x55/0x80
>  [<ffffffff8103a902>] arch_ptrace+0xe2/0x370
>  [<ffffffff81074c18>] sys_ptrace+0x68/0xc0
>  [<ffffffff815c3e1f>] ? page_fault+0x1f/0x30
>  [<ffffffff8102ee2b>] system_call_fastpath+0x16/0x1b
> Code: 00 00 00 55 48 89 e5 41 57 41 56 41 55 41 54 49 89 f4 53 48 89 fb
> 48 83 ec 28 44 8b b6 dc 01 00 00 48 8b 86 80 01 00 00 45 85 f6 <4c> 8b
> a8 80 00 00 00 78 5f 48 c7 c0 d8 e2 00 00 4d 63 f6 4a 8b
> RIP  [<ffffffff810c5c08>] fetch_bp_busy_slots.clone.1+0x28/0x1c0
>  RSP <ffff8801b71a3ca8>
> CR2: 0000000000000080
> ---[ end trace 8199f8c45e224e74 ]---
> psi[18938] trap int3 ip:7ffff3bdaa01 sp:7fffffffccc8 error:0
> 
> Is there a pacth for this already? Or should I investigate further?
> 
> regards,
> -- 
> js
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