netdev - sysctl: setting key "net.core.bpf_jit

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Message-ID: <412d88b2-fa9a-149e-6f6e-3cfbce9edef0@molgen.mpg.de>
Date:   Sun, 11 Apr 2021 13:09:07 +0200
From:   Paul Menzel <pmenzel@...gen.mpg.de>
To:     "Naveen N. Rao" <naveen.n.rao@...ux.ibm.com>,
        Sandipan Das <sandipan@...ux.ibm.com>
Cc:     netdev@...r.kernel.org, bpf@...r.kernel.org,
        linuxppc-dev@...ts.ozlabs.org, it+linux-bpf@...gen.mpg.de
Subject: sysctl: setting key "net.core.bpf_jit_enable": Invalid argument

Dear Linux folks,

Related to * [CVE-2021-29154] Linux kernel incorrect computation of 
branch displacements in BPF JIT compiler can be abused to execute 
arbitrary code in Kernel mode* [1], on the POWER8 system IBM S822LC with 
self-built Linux 5.12.0-rc5+, I am unable to disable `bpf_jit_enable`.

     $ /sbin/sysctl net.core.bpf_jit_enable
     net.core.bpf_jit_enable = 1
     $ sudo /sbin/sysctl -w net.core.bpf_jit_enable=0
     sysctl: setting key "net.core.bpf_jit_enable": Invalid argument

It works on an x86 with Debian sid/unstable and Linux 5.10.26-1.

Kind regards,

Paul

[1]: https://seclists.org/oss-sec/2021/q2/12