*** This bug is a duplicate of bug 1909286 ***
https://bugs.launchpad.net/bugs/1909286
Krzysztof mentioned that this has been found on 5.14 as well. Using a
system he lent me (huggins), I also tested with the commit that changed
the call to use CTR and it failed as well. But it always failed when
__bpf_prog_run_save_cb was calling the jited bpf_func, and CTR always
matched NIP (though in that case, it is the CTR from
__bpf_prog_run_save_cb, not the JITed code). Sometimes it was NULL (all
zeroes), sometimes it looked like a legit kernel address, and I got one
0xfe800000fe80000000 (or something like it), which looks like some
corruption on bpf_prog.
Also, I noticed it doesn't happen always on CPU 0, which would be odd on
its own. But it seems more likely. And it's either very hard to
reproduce without doing the CPU hotplug or it is really necessary, and I
left the program running on a loop for a long time and did not have any
luck.
I also changed it to an eBPF program instead of cBPF, but still a socket
filter type. And used get_smp_processor_id instead of the
raw_processor_id (though I recall this being the same on ppc64el), and
it still reproduced. And when I returned a constant instead of doing the
call, it also reproduced. No wonder, as when it fails, the program never
runs. But the way those programs are compiled makes no difference.
Cascardo.
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https://bugs.launchpad.net/bugs/1927076
Title:
IPv6 TCP in reuseport_bpf_cpu from ubuntu_kernel_selftests/net crash
P8 node entei on 5.8 kernel (Oops: Exception in kernel mode, sig: 4
[#1])
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