Re: SMP races in proc with thread_struct

Andreas Schwab
2001-05-04T13:26:09Z

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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