[OOPS] 2.6.12-rc3 ptrace bug?

["Udo A. Steinberg" <us15@os.inf.tu-dresden.de>]

The attached (radically shortened) program to measure pipe performance oopses
the Linux-2.6.12-rc3 kernel when traced using "strace -f". The problem no longer
occurs in -rc4 or -rc5. It would be good to know whether the bug causing the
problem is known and has been fixed or simply went away due to other changes.
I have been unable to find a Changelog detailing the patches that went
into -rc4.

The bug is reproducible on all -rc3 kernels I've tried.

Unable to handle kernel NULL pointer dereference at virtual address 00000000
 printing eip:
00000000
*pde = 00000000
Oops: 0000 [#1]
PREEMPT 
Modules linked in:
CPU:    0
EIP:    0060:[<00000000>]    Not tainted VLI
EFLAGS: 00010286   (2.6.12-rc3) 
EIP is at 0x0
eax: db052000   ebx: 01200011   ecx: 00000000   edx: 00000000
esi: df605060   edi: 00000000   ebp: db052000   esp: db052fc4
ds: 007b   es: 007b   ss: 0068
Process pipe (pid: 778, threadinfo=db052000 task=df605060)
Stack: 01202011 00000000 00000000 00000000 b7ea0708 bf9da748 00000000 0000007b 
       c010007b 00000078 b7f290a5 00000073 00000282 bf9da6e0 0000007b 
Call Trace:
Code:  Bad EIP value.

Best regards,
-Udo.

Attachment: pipe.c
Description: Binary data

Attachment: pgpuIAgq8IfXk.pgp
Description: PGP signature