Re: [PATCH] namespaces: fix race at task exit

[Cedric Le Goater]

Serge E. Hallyn wrote:
> In do_exit(), the exit_task_namespaces() was placed after
> exit_notify() because exit_notify ends up using the pid
> namespace both to access the reaper, and for detaching the
> pid.  However, this placement allows an nfs server to reap
> the task before exit_task_namespaces() completes.
> 
> This patch moves the exit_task_namespaces() into release_task,
> below release_thread() which puts the pids(), and just above
> the call_rcu(delayed_put_task_struct).  I believe this should
> solve both problems.
> 
> Signed-off-by: Serge E. Hallyn <serue@xxxxxxxxxx>

I've run some tests on x86 and x86_64: mounted a NFS share after 
having unshare(CLONE_NEWNS) and I didn't reproduce the bug Daniel 
had found. 

it looks safe.

C.
 

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