netdev - Re: bpf_test

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Message-ID: <a7f18cfe-049c-d580-8c15-5d09b6860c48@fb.com>
Date:   Mon, 1 May 2017 21:46:07 -0700
From:   Alexei Starovoitov <ast@...com>
To:     David Miller <davem@...emloft.net>
CC:     <daniel@...earbox.net>, <netdev@...r.kernel.org>
Subject: Re: bpf_test_finish()

On 5/1/17 8:56 PM, David Miller wrote:
>
> It dereferences a user pointer:
>
> static int bpf_test_finish(union bpf_attr __user *uattr, const void *data,
> 			   u32 size, u32 retval, u32 duration)
> {
> 	void __user *data_out = u64_to_user_ptr(uattr->test.data_out);
>                                                 ^^^^^^^^^^^^^^^^^^^^
> Which of course doesn't work so well :-)
>
> I really wish that didn't silently work on x86/x86_64.

argh. my bad.
I'll send a patch first thing tomorrow unless Daniel beats me to it.
We have kattr there as well which has the whole bpf_attr copied into
kernel memory already. Should have taken data_out from there and
passed into bpf_test_finish().