Re: SMP races in proc with thread_struct

[Andreas Schwab <schwab@suse.de>]

Keith Owens <kaos@ocs.com.au> writes:

|> On Fri, 04 May 2001 07:34:20 -0500, 
|> Todd Inglett <tinglett@vnet.ibm.com> wrote:
|> >But this is where hell breaks loose.  Every process has a valid parent
|> >-- unless it is dead and nobody cares.  Process N has already exited and
|> >released from the tasklist while its parent was still alive.  There was
|> >no reason to reparent it.  It just got released.  So N's task_struct has
|> >a dangling ptr to its parent.  Nobody is holding the parent task_struct,
|> >either.  When the parent died memory for its task_struct was released. 
|> >This is ungood.
|> 
|> Wrap the reference to the parent task structure with exception table
|> recovery code, like copy_from_user().

Exception tables only protect accesses to user virtual memory.  Kernel
memory references must always be valid in the first place.

Andreas.

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