linux-kernel - Re: [PATCH 3/3] bpf: Make sure that ->comm does not change under us.

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Message-ID: <3636052.F7cf4ubS1t@blindfold>
Date:   Mon, 16 Oct 2017 22:55:43 +0200
From:   Richard Weinberger <richard@....at>
To:     Daniel Borkmann <daniel@...earbox.net>
Cc:     netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        ast@...nel.org
Subject: Re: [PATCH 3/3] bpf: Make sure that ->comm does not change under us.

Am Montag, 16. Oktober 2017, 22:50:43 CEST schrieb Daniel Borkmann:
> >   	struct task_struct *task = current;
> > 
> > +	task_lock(task);
> > 
> >   	strncpy(buf, task->comm, size);
> > 
> > +	task_unlock(task);
> 
> Wouldn't this potentially lead to a deadlock? E.g. you attach yourself
> to task_lock() / spin_lock() / etc, and then the BPF prog triggers the
> bpf_get_current_comm() taking the lock again ...

Yes, but doesn't the same apply to the use case when I attach to strncpy()
and run bpf_get_current_comm()?

Thanks,
//richard