Messages in this thread | ![/](/images/icornerl.gif) | | Date | Thu, 19 Jan 2023 21:48:23 -0800 | From | Alexei Starovoitov <> | Subject | Re: [PATCH bpf-next 4/8] bpf: Enable cpumasks to be queried and used as kptrs |
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On Thu, Jan 19, 2023 at 05:58:29PM -0600, David Vernet wrote: > silently check for and ignore these cases at runtime. When we have e.g. > per-argument kfunc flags, it might be helpful to add another KF_CPU-type > flag that specifies that the verifier should validate that it's a valid > CPU.
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> +void bpf_cpumask_set_cpu(u32 cpu, struct bpf_cpumask *cpumask) > +{ > + if (!cpu_valid(cpu)) > + return; > + > + cpumask_set_cpu(cpu, (struct cpumask *)cpumask); > +}
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> +void bpf_cpumask_clear_cpu(u32 cpu, struct bpf_cpumask *cpumask) > +{ > + if (!cpu_valid(cpu)) > + return;
I don't think we'll be able to get rid of this with KF_CPU or special suffix. The argument might be a variable and not a constant at the verification time. We would have to allow passing unknown vars otherwise the UX will be too restrictive, so this run-time check would have to stay.
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