Date: Sat, 26 May 2018 19:30:47 +0200 From: Salvatore Mesoraca <s.mesoraca16@...il.com> To: 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 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? Thank you, Salvatore
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