Date: Sat, 26 May 2018 18:33:23 -0700 From: Linus Torvalds <torvalds@...ux-foundation.org> To: Kees Cook <keescook@...omium.org> Cc: Salvatore Mesoraca <s.mesoraca16@...il.com>, Jann Horn <jannh@...gle.com>, Kernel Hardening <kernel-hardening@...ts.openwall.com>, LSM List <linux-security-module@...r.kernel.org>, Linux Kernel Mailing List <linux-kernel@...r.kernel.org>, linux-mm <linux-mm@...ck.org>, Andrew Morton <akpm@...ux-foundation.org>, Alexey Dobriyan <adobriyan@...il.com>, Akinobu Mita <akinobu.mita@...il.com>, Dmitry Vyukov <dvyukov@...gle.com>, Arnd Bergmann <arnd@...db.de>, Davidlohr Bueso <dave@...olabs.net> Subject: Re: [PATCH] proc: prevent a task from writing on its own /proc/*/mem On Sat, May 26, 2018 at 5:32 PM Kees Cook <keescook@...omium.org> wrote: > I went through some old threads from 2012 when e268337dfe26 was > introduced, and later when things got looked at during DirtyCOW. There > was discussion about removing FOLL_FORCE (in order to block writes on > a read-only memory region). Side note, we did that for /dev/mem, and things broke. Thus commit f511c0b17b08 "Yes, people use FOLL_FORCE ;)" Side note, that very sam ecommit f511c0b17b08 is also the explanation for why the patch under discussion now seems broken. People really do use "write to /proc/self/mem" as a way to keep the mappings read-only, but have a way to change them when required. Linus
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