linux-kernel - BPF RNG

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Message-ID: <CAGXu5jL6LVU7KyUvwaEHWE6t2TaVBs5TWNayB5cW2=PWzSMyEw@mail.gmail.com>
Date:   Tue, 16 Apr 2019 08:54:27 -0500
From:   Kees Cook <keescook@...gle.com>
To:     Daniel Borkmann <daniel@...earbox.net>
Cc:     Hannes Frederic Sowa <hannes@...essinduktion.org>,
        Alexei Starovoitov <ast@...mgrid.com>,
        LKML <linux-kernel@...r.kernel.org>,
        Ingo Molnar <mingo@...nel.org>,
        "Reshetova, Elena" <elena.reshetova@...el.com>
Subject: BPF RNG

Hi,

In looking at prandom_u32() users, I noticed that BPF uses its own
state variable with bpf_user_rnd_u32(). It appears that this state is
never reseeded like regular prandom_u32(). (See __prandom_timer().) Is
this intentional, or should reseeding be happening?

-Kees

-- 
Kees Cook