netdev - Re: [PATCH bpf-next] bpf: Fix trampoline usage in preempt

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Message-ID: <1ab7d6f3-fc97-cb29-cf77-7d0d9b70e9ca@iogearbox.net>
Date:   Wed, 22 Jan 2020 16:55:34 +0100
From:   Daniel Borkmann <daniel@...earbox.net>
To:     Alexei Starovoitov <ast@...nel.org>, davem@...emloft.net
Cc:     jannh@...gle.com, paulmck@...nel.org, netdev@...r.kernel.org,
        bpf@...r.kernel.org, kernel-team@...com
Subject: Re: [PATCH bpf-next] bpf: Fix trampoline usage in preempt

On 1/21/20 4:22 AM, Alexei Starovoitov wrote:
> Though the second half of trampoline page is unused a task could be
> preempted in the middle of the first half of trampoline and two
> updates to trampoline would change the code from underneath the
> preempted task. Hence wait for tasks to voluntarily schedule or go
> to userspace.
> Add similar wait before freeing the trampoline.
> 
> Fixes: fec56f5890d9 ("bpf: Introduce BPF trampoline")
> Reported-by: Jann Horn <jannh@...gle.com>
> Signed-off-by: Alexei Starovoitov <ast@...nel.org>

Applied, thanks!