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

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Message-ID: <59102FFE.8000701@iogearbox.net>
Date:   Mon, 08 May 2017 10:44:46 +0200
From:   Daniel Borkmann <daniel@...earbox.net>
To:     davem@...emloft.net
CC:     alexei.starovoitov@...il.com, jannh@...gle.com, kafai@...com,
        netdev@...r.kernel.org
Subject: Re: [PATCH net] bpf: don't let ldimm64 leak map addresses on unprivileged

On 05/08/2017 12:04 AM, 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().

This one is also needed for the log (should come first):

Fixes: 1be7f75d1668 ("bpf: enable non-root eBPF programs")

> 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,
Daniel