Date: Sat, 26 May 2018 10:53:04 -0700 From: Casey Schaufler <casey@...aufler-ca.com> To: Salvatore Mesoraca <s.mesoraca16@...il.com>, Alexey Dobriyan <adobriyan@...il.com> Cc: Kernel Hardening <kernel-hardening@...ts.openwall.com>, linux-security-module@...r.kernel.org, linux-kernel@...r.kernel.org, linux-mm@...ck.org, Andrew Morton <akpm@...ux-foundation.org>, Akinobu Mita <akinobu.mita@...il.com>, Dmitry Vyukov <dvyukov@...gle.com>, Arnd Bergmann <arnd@...db.de>, Davidlohr Bueso <dave@...olabs.net>, Kees Cook <keescook@...omium.org> Subject: Re: [PATCH] proc: prevent a task from writing on its own /proc/*/mem On 5/26/2018 10:30 AM, Salvatore Mesoraca wrote: > 2018-05-26 17:48 GMT+02:00 Alexey Dobriyan <adobriyan@...il.com>: >> 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@...r.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html >
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