netdev - Re: [PATCH net-next v2] net: bpf: make eBPF interpreter images read-only

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Date:	Tue, 2 Sep 2014 14:31:47 -0700
From:	Alexei Starovoitov <ast@...mgrid.com>
To:	Hannes Frederic Sowa <hannes@...essinduktion.org>
Cc:	Network Development <netdev@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Brad Spengler <spender@...ecurity.net>,
	Daniel Borkmann <dborkman@...hat.com>,
	Kees Cook <keescook@...omium.org>
Subject: Re: [PATCH net-next v2] net: bpf: make eBPF interpreter images read-only

On Tue, Sep 2, 2014 at 1:53 PM, Hannes Frederic Sowa
<hannes@...essinduktion.org> wrote:
> From: Daniel Borkmann <dborkman@...hat.com>
>
> With eBPF getting more extended and exposure to user space is on it's way,
> hardening the memory range the interpreter uses to steer its command flow
> seems appropriate.  This patch moves the to be interpreted bytecode to
> read-only pages.
...
>  11 files changed, 144 insertions(+), 32 deletions(-)

nice. quite short.

> +#ifdef CONFIG_DEBUG_SET_MODULE_RONX
> +static inline void bpf_prog_lock_ro(struct bpf_prog *fp)
> +{
> +       set_memory_ro((unsigned long)fp, fp->pages);

since ronx are ifdef checked together,
would probably make sense to set nx too?

> +static inline void bpf_prog_unlock_ro(struct bpf_prog *fp)
> +{
> +       set_memory_rw((unsigned long)fp, fp->pages);

why rw is needed?
since fp is allocated with vmalloc, vfree doesn't need
to touch the pages to free them, no?
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