netdev - Re: [PATCH net] bpf: don't let ldimm64 leak map addresses on unprivileged

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Message-ID: <20170508171838.t5v32fazpiiadji2@ast-mbp.dhcp.thefacebook.com>
Date:   Mon, 8 May 2017 10:18:40 -0700
From:   Alexei Starovoitov <alexei.starovoitov@...il.com>
To:     Daniel Borkmann <daniel@...earbox.net>
Cc:     davem@...emloft.net, jannh@...gle.com, kafai@...com,
        netdev@...r.kernel.org
Subject: Re: [PATCH net] bpf: don't let ldimm64 leak map addresses on
 unprivileged

On Mon, May 08, 2017 at 12:04:09AM +0200, Daniel Borkmann wrote:
> The patch fixes two things at once:
> 
> 1) It checks the env->allow_ptr_leaks and only prints the map address to
>    the log if we have the privileges to do so, otherwise it just dumps 0
>    as we would when kptr_restrict is enabled on %pK. Given the latter is
>    off by default and not every distro sets it, I don't want to rely on
>    this, hence the 0 by default for unprivileged.
> 
> 2) Printing of ldimm64 in the verifier log is currently broken in that
>    we don't print the full immediate, but only the 32 bit part of the
>    first insn part for ldimm64. Thus, fix this up as well; it's okay to
>    access, since we verified all ldimm64 earlier already (including just
>    constants) through replace_map_fd_with_map_ptr().
> 
> Fixes: cbd357008604 ("bpf: verifier (add ability to receive verification log)")
> Reported-by: Jann Horn <jannh@...gle.com>
> Signed-off-by: Daniel Borkmann <daniel@...earbox.net>

thanks for the fix!

Acked-by: Alexei Starovoitov <ast@...nel.org>