linux-kernel - Re: [PATCH v3] bpf: Set register type according to is_valid

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Message-ID: <57E9356D.70308@iogearbox.net>
Date:   Mon, 26 Sep 2016 16:49:17 +0200
From:   Daniel Borkmann <daniel@...earbox.net>
To:     Mickaël Salaün <mic@...ikod.net>,
        linux-kernel@...r.kernel.org
CC:     Alexei Starovoitov <ast@...nel.org>,
        Andy Lutomirski <luto@...capital.net>,
        Kees Cook <keescook@...omium.org>,
        Sargun Dhillon <sargun@...gun.me>, Tejun Heo <tj@...nel.org>,
        netdev@...r.kernel.org
Subject: Re: [PATCH v3] bpf: Set register type according to is_valid_access()

On 09/24/2016 08:01 PM, Mickaël Salaün wrote:
> This prevent future potential pointer leaks when an unprivileged eBPF
> program will read a pointer value from its context. Even if
> is_valid_access() returns a pointer type, the eBPF verifier replace it
> with UNKNOWN_VALUE. The register value that contains a kernel address is
> then allowed to leak. Moreover, this fix allows unprivileged eBPF
> programs to use functions with (legitimate) pointer arguments.
>
> Not an issue currently since reg_type is only set for PTR_TO_PACKET or
> PTR_TO_PACKET_END in XDP and TC programs that can only be loaded as
> privileged. For now, the only unprivileged eBPF program allowed is for
> socket filtering and all the types from its context are UNKNOWN_VALUE.
> However, this fix is important for future unprivileged eBPF programs
> which could use pointers in their context.
>
> Signed-off-by: Mickaël Salaün <mic@...ikod.net>
> Cc: Alexei Starovoitov <ast@...nel.org>
> Cc: Daniel Borkmann <daniel@...earbox.net>

Seems okay to me:

Acked-by: Daniel Borkmann <daniel@...earbox.net>