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Sat, 26 May 2018 13:53:13 -0400 Received: from sonic313-26.consmr.mail.gq1.yahoo.com ([98.137.65.89]:42456 "EHLO sonic313-26.consmr.mail.gq1.yahoo.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1032115AbeEZRxM (ORCPT ); Sat, 26 May 2018 13:53:12 -0400 X-YMail-OSG: m4YGGE0VM1kyTL9g.lgw83ZLkNDly6unPNA5wpQnigdWflt3E2INhsmzPozvpfU if4pZ2Z_Hw.509sEPUOAd6sJFWblTz9L4LOuBlJPbYsrYmrpb2Mus37EXIvK8KhqmPwonrnmP0Dn dEooyyVH1F64d2_R0W8dIiz.tSaXLnmiNf.p.GDECkEb2TTdGpsoKmgwBNLbkNCbaTT2HahdzA56 faC.ywP8EQzmHEwsRdmayyQP5v.3vxznb9YfKGpTHrp6Q4XKNMy55e9lEedQYetO9_XmRhpaXQlo 7M_zvKqz7pMlrGrEmf.5bgQtYUUlLPGdVYlRicDqvfu0quLc_3SqJZZKaSIFsJPzGF12K6xj0KLz Sde2EQKzO4bA48HSUMddkduoqmUVVsD76nFam1PXPx7fzvJHpxlEd7uVN1pwQvLI4rVmKl6d7adT YesOos8E6eT4yZKQoEuyU7J2piseNmKwYXK2j12Jd2DQWZToC24OFkTdgtDZbHTB8cNpD5RExQUL Sh_Ra1Py.49lIflFARtkKx553wSsvn6PmpgvzZGX.PUN0YKtI9UP7sBZgzdT7BY1cF9x_9xUbVL6 kERr45UNAo5G65uvzsLdiOw7E.lQ9sT.JNvbuq17pWKN78ang1XLYBQb6aSPdwufKIFnP46cyFFs hbTBB.lkyDRvZ95s.6cpKu74KufaCxe2MfVo390t2UcF_lQM2SUckuFrxoX2e5U_MhZNLSByjcCO VfAxvw0O4LRpBNwpypwLnJAMrTSGPzg-- Subject: Re: [PATCH] proc: prevent a task from writing on its own /proc/*/mem To: Salvatore Mesoraca , Alexey Dobriyan Cc: Kernel Hardening , linux-security-module@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, Andrew Morton , Akinobu Mita , Dmitry Vyukov , Arnd Bergmann , Davidlohr Bueso , Kees Cook References: <1527346246-1334-1-git-send-email-s.mesoraca16@gmail.com> <20180526154819.GA14016@avx2> From: Casey Schaufler Message-ID: Date: Sat, 26 May 2018 10:53:04 -0700 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:52.0) Gecko/20100101 Thunderbird/52.8.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Content-Language: en-US Sender: owner-linux-security-module@vger.kernel.org X-getmail-retrieved-from-mailbox: INBOX X-Mailing-List: linux-kernel@vger.kernel.org List-ID: On 5/26/2018 10:30 AM, Salvatore Mesoraca wrote: > 2018-05-26 17:48 GMT+02:00 Alexey Dobriyan : >> On Sat, May 26, 2018 at 04:50:46PM +0200, Salvatore Mesoraca wrote: >>> Prevent a task from opening, in "write" mode, any /proc/*/mem >>> file that operates on the task's mm. >>> /proc/*/mem is mainly a debugging means and, as such, it shouldn't >>> be used by the inspected process itself. >>> Current implementation always allow a task to access its own >>> /proc/*/mem file. >>> A process can use it to overwrite read-only memory, making >>> pointless the use of security_file_mprotect() or other ways to >>> enforce RO memory. >> You can do it in security_ptrace_access_check() > No, because that hook is skipped when mm == current->mm: > https://elixir.bootlin.com/linux/v4.17-rc6/source/kernel/fork.c#L1111 > >> or security_file_open() > This is true, but it looks a bit overkill to me, especially since many of > the macros/functions used to handle proc's files won't be in scope > for an external LSM. > Is there any particular reason why you prefer it done via LSM? If you did a Yama style LSM it would be easy to configure. Even though it might make no sense to allow this behavior, someone, somewhere is counting on it. > > Thank you, > > Salvatore > -- > To unsubscribe from this list: send the line "unsubscribe linux-security-module" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html >