Re: [RFC 1/2] proc: Return if nothing to unmount

From: Rik van Riel
Date: Sun Sep 10 2017 - 16:08:07 EST

On September 9, 2017 2:31:35 PM EDT, Al Viro <viro@xxxxxxxxxxxxxxxxxx> wrote:
>On Sat, Sep 09, 2017 at 06:03:16PM +0530, Gargi Sharma wrote:
>> If a task exits before procfs is mounted, proc_flush_task_mnt will
>> be called with a NULL mnt parameter. In that case, not only is there
>> nothing to unhash, but trying to do so will oops the kernel with a
>> null pointer dereference.
>You are misreading that sucker. It's about userland mounts, it's about
>the internal ones in pidns, for each pidns the process belongs to.
>IOW, what you are adding is dead code. The very first alloc_pid() in
>that pidns should've called pid_ns_prepare_proc(), which creates that

Huh, my bad. I wonder why Gargi's code ran into a null pointer dereference on a null mnt pointer, then...
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