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

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Message-ID: <54063AF1.4020907@redhat.com>
Date:	Tue, 02 Sep 2014 23:47:29 +0200
From:	Daniel Borkmann <dborkman@...hat.com>
To:	Alexei Starovoitov <ast@...mgrid.com>
CC:	Hannes Frederic Sowa <hannes@...essinduktion.org>,
	Network Development <netdev@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Brad Spengler <spender@...ecurity.net>,
	Kees Cook <keescook@...omium.org>
Subject: Re: [PATCH net-next v2] net: bpf: make eBPF interpreter images read-only

On 09/02/2014 11:31 PM, Alexei Starovoitov wrote:
...
>> +#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?

In case of JITs, for example, we request pages that are
PAGE_KERNEL_EXEC via module_alloc(), but here we only need
PAGE_KERNEL. At least on x86_64, PAGE_NX is then set already.
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