Messages in this thread | | | From | Linus Torvalds <> | Date | Sat, 16 Apr 2022 13:30:47 -0700 | Subject | Re: [PATCH v4 bpf 0/4] vmalloc: bpf: introduce VM_ALLOW_HUGE_VMAP |
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On Sat, Apr 16, 2022 at 12:55 PM Song Liu <songliubraving@fb.com> wrote: > > Based on this analysis, I think we should either > 1) ship the whole set with 5.18; or > 2) ship 1/4, 3/4, and 4/4 with 5.18, and 2/4 with 5.19.
Honestly, I think the proper thing to do is
- apply #1, because yes, that "use huge pages" should be an opt-in.
- but just disable hugepages for now.
I think those games with set_memory_nx() and friends just show how rough this all is right now.
In fact, I personally think that the whole bpf 'prog_pack' stuff should probably be disabled. It looks incredible broken to me right now.
Unless I mis-read it, it does a "module_alloc()" to allocate the vmap area, and then just marks it executable without having even initialized the pages. Am I missing something? So now we have random kernel memory that is marked executable.
Sure, it's also marked RO, but who cares? It's random data that is now executable.
Maybe I am missing something, but I really don't think this is ready for prime-time. We should effectively disable it all, and have people think through it a lot more.
Linus
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