From mboxrd@z Thu Jan 1 00:00:00 1970 From: Linus Torvalds Subject: Re: [PATCH 0/9] proc: protect /proc//* files across execve Date: Sat, 10 Mar 2012 16:01:09 -0800 Message-ID: References: <1331421919-15499-1-git-send-email-tixxdz@opendz.org> Reply-To: kernel-hardening@lists.openwall.com Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Cc: linux-kernel@vger.kernel.org, kernel-hardening@lists.openwall.com, Andrew Morton , Al Viro , Alexey Dobriyan , "Eric W. Biederman" , Vasiliy Kulikov , Kees Cook , Solar Designer , WANG Cong , James Morris , Oleg Nesterov , linux-security-module@vger.kernel.org, linux-fsdevel@vger.kernel.org, Alan Cox , Greg KH , Ingo Molnar , Stephen Wilson , "Jason A. Donenfeld" To: Djalal Harouni Return-path: List-Post: List-Help: List-Unsubscribe: List-Subscribe: Sender: linus971@gmail.com In-Reply-To: <1331421919-15499-1-git-send-email-tixxdz@opendz.org> List-Id: linux-fsdevel.vger.kernel.org On Sat, Mar 10, 2012 at 3:25 PM, Djalal Harouni wrote: > > 1) Use the target exec_id to bind files to their exec_id task: > > For the REG files /proc//{environ,pagemap,mem} we set the exec_id > of the proc_file_private to the target task, and we continue with > permission checks at open time, later on each read/write call the > permission checks are done + check the target exec_id if it equals the > exec_id of the proc_file_private that was set at open time, in other words > we bind the file to its task's exec_id, this way new exec programs can not > operate on the passed fd. So the exec_id approach was totally broken when it was used for /proc//mem, is there any reason to believe it's a good idea now? It's entirely predictable, and you can make the exec_id match by simply forking elsewhere and then passing the fd around using unix domain sockets, since the exec_id is just updated by incrementing a counter. I would in general suggest strongly against using exec_id for anything that involves files. It isn't designed for that, it's designed for the whole "check the parent exec_id" thing for ptrace, where that whole "pass things around to another process" approach doesn't work. Linus