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Subject: Re: [PATCH bpf-next] bpf: Fix trampoline usage in preempt
To:     Alexei Starovoitov <ast@kernel.org>, davem@davemloft.net
Cc:     jannh@google.com, paulmck@kernel.org, netdev@vger.kernel.org,
        bpf@vger.kernel.org, kernel-team@fb.com
References: <20200121032231.3292185-1-ast@kernel.org>
From:   Daniel Borkmann <daniel@iogearbox.net>
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Date:   Wed, 22 Jan 2020 16:55:34 +0100
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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@google.com>
> Signed-off-by: Alexei Starovoitov <ast@kernel.org>

Applied, thanks!