linux-kernel - Re: [PATCH] MIPS: Prevent READ_IMPLIES

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Date:   Tue, 7 Jul 2020 20:45:38 +0100 (BST)
From:   "Maciej W. Rozycki" <macro@....com>
To:     Tiezhu Yang <yangtiezhu@...ngson.cn>
cc:     Thomas Bogendoerfer <tsbogend@...ha.franken.de>,
        linux-mips@...r.kernel.org, linux-kernel@...r.kernel.org,
        Kees Cook <keescook@...omium.org>,
        Xuefeng Li <lixuefeng@...ngson.cn>,
        Juxin Gao <gaojuxin@...ngson.cn>,
        "Maciej W. Rozycki" <macro@...ux-mips.org>
Subject: Re: [PATCH] MIPS: Prevent READ_IMPLIES_EXEC propagation

On Tue, 7 Jul 2020, Tiezhu Yang wrote:

> In the MIPS architecture, we should clear the security-relevant
> flag READ_IMPLIES_EXEC in the function SET_PERSONALITY2() of the
> file arch/mips/include/asm/elf.h.
> 
> Otherwise, with this flag set, PROT_READ implies PROT_EXEC for
> mmap to make memory executable that is not safe, because this
> condition allows an attacker to simply jump to and execute bytes
> that are considered to be just data [1].

 Why isn't the arrangement made with `mips_elf_read_implies_exec' 
sufficient?

  Maciej