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From: Rudi Ratloser <reimth@gmail.com>
To: bpf@vger.kernel.org
Subject: Re: BUG: kernel NULL pointer dereference in __cgroup_bpf_run_filter_skb
Date: Tue, 30 Jun 2020 16:28:49 +0200
Message-ID: <CAOLRBTUSkRbku25rbw6Fyb019wFqFvEN=6xGM+RgFJFQ=NH4KQ@mail.gmail.com> (raw)

We have experienced a kernel BPF null pointer dereference issue on all
our machines since mid of June. It might be related to an upgrade of
libvirt/kvm/qemu at that point of time. But we’re not sure.

None of the servers can be used with this bug, as they crash latest
one hour after reboot. The time period until kernel panic can be
easily reduced down to 2 minutes, when starting one or more
applications of the following list:
- LXD daemon (4.2.1)
- libvirtd daemon (6.4.0) with qemu/kvm guests
- NFS server 2.5.1
- Mozilla Firefox
- Mozilla Thunderbird

If none of the applications run, the systems seem to be stable.

Intermediate solution:
Downgrade Linux kernel to 4.9.226 LTS or 4.4.226  LTS on all the machines

Why this solution works is not clear, yet. One of the major
differences we saw is, that both kernel packages have been configured
with user namespaces disabled.

We experienced the kernel freeze on following Arch Linux kernels:
- 5.7.0 (5.7.0-3-MANJARO x64)
- 5.6.16 (5.6.16-1-MANJARO x64)
- 5.4.44 (5.4.44-1-MANJARO x64)
- 4.19.126 (4.19.126-1-MANJARO x64)
- 4.14.183 (4.14.183-1-MANJARO x64)
Kernel configs can be taken from https://gitlab.manjaro.org/packages/core.

Subsequent e-mails will contain the relevant extracts from journal or
netconsole logs.

Help and support on this issue is welcome.

             reply index

Thread overview: 14+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-06-30 14:28 Rudi Ratloser [this message]
2020-06-30 14:56 ` Daniel Borkmann
2020-07-01  7:08   ` Thomas Reim
2020-07-01  6:46 ` Thomas Reim
2020-07-01  6:51 ` Thomas Reim
2020-07-01  6:58 ` Thomas Reim
  -- strict thread matches above, loose matches on Subject: below --
2020-06-30 15:11 Rudi Ratloser
     [not found] <20200530074608.GA60664@fnst.localdomain>
2020-06-02 21:46 ` Brenden Blanco
2020-06-02 22:17   ` Alexei Starovoitov
2020-06-03  6:20     ` Lu Fengqi
2020-06-03  8:22       ` Lu Fengqi
2020-06-09 20:50     ` Daniel Borkmann
2020-06-10  1:37       ` Zefan Li
2020-06-03  6:16   ` Lu Fengqi

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