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Shutemov" , Michel Lespinasse , Michal =?iso-8859-1?Q?Koutn=FD?= , Song Liu , Huang Ying , Vlastimil Babka , Yang Shi , chenqiwu , Mathieu Desnoyers , John Hubbard , Thomas Hellstrom , Mike Christie , Bart Van Assche , Amit Pundir , Thomas Gleixner , Christian Brauner , Daniel Jordan , Adrian Reber , Nicolas Viennot , Al Viro , Thomas Cedeno , linux-fsdevel@vger.kernel.org, Pekka Enberg , Peter Zijlstra , Ingo Molnar , Oleg Nesterov , "Eric W. Biederman" , Jan Glauber , John Stultz , Rob Landley , "Serge E. Hallyn" , David Rientjes , Hugh Dickins , Rik van Riel , Mel Gorman , Tang Chen , Robin Holt , Shaohua Li , Sasha Levin , Johannes Weiner , Minchan Kim Subject: Re: [PATCH v5 2/2] mm: add a field to store names for private anonymous memory Message-ID: <20200820215903.GU2074@grain> References: <20200819141650.7462-1-sumit.semwal@linaro.org> <20200819141650.7462-3-sumit.semwal@linaro.org> <20200820214003.GR2074@grain> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.14.6 (2020-07-11) X-Rspamd-Queue-Id: E092A18086CDA X-Spamd-Result: default: False [0.00 / 100.00] X-Rspamd-Server: rspam03 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Thu, Aug 20, 2020 at 02:45:38PM -0700, Dave Hansen wrote: > > > > Guys, could you please enlighen me, I don't understand -- we pass some > > random user-space pointer and save it in vm_area_struct then in procfs > > we treat it as "string" and print out? What prevents me to put some crap > > here then unmap this pointer the kernel will cause page fault in procfs > > output (in best scenario)? > > Remember, this is virtually identical to what we do for > /proc/$pid/cmdline in get_mm_cmdline(). The kernel goes following a > user-provided pointer into the user address space looking for a string. > > If userspace points it to garbage, access_remote_vm() will fail safely. Yeah, managed to miss it, thanks!