linux-kernel - Question related to ( commit 9f691549f76d "bpf: fix struct htab

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Message-ID: <CAK+bU8e_mue_-a4cm85THkg=MyNOf6O2so4D+22wzG_LPu=4LA@mail.gmail.com>
Date:   Mon, 30 Aug 2021 10:16:37 -0400
From:   Etienne Martineau <etmartin101@...il.com>
To:     ast@...com, jonperry@...com, daniel@...earbox.net,
        fengc@...gle.com, sashal@...nel.org
Cc:     linux-kernel@...r.kernel.org,
        Etienne Martineau <etmartin101@...il.com>
Subject: Question related to ( commit 9f691549f76d "bpf: fix struct htab_elem
 layout" )

Hi,

I've been staring at this commit for some time and I wonder what were the
symptoms when the issue was reproduced?
  "The bug was discovered by manual code analysis and reproducible
    only with explicit udelay() in lookup_elem_raw()."

I tried various stress test + timing combinations in lookup_elem_raw() but no
luck.

I believe that one of our production boxes ran into that issue lately with a GPF
in the area of htab_map_lookup_elem(). The crash was seen on an outdated
4.9 stable.

Please CC me as I'm not on the list.

thanks in advance,
Etienne