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Message-ID: <20120311170125.GA10787@dztty> Date: Sun, 11 Mar 2012 18:01:25 +0100 From: Djalal Harouni <tixxdz@...ndz.org> To: Alexey Dobriyan <adobriyan@...il.com> Cc: linux-kernel@...r.kernel.org, kernel-hardening@...ts.openwall.com, Andrew Morton <akpm@...ux-foundation.org>, Linus Torvalds <torvalds@...ux-foundation.org>, Al Viro <viro@...iv.linux.org.uk>, "Eric W. Biederman" <ebiederm@...ssion.com>, Vasiliy Kulikov <segoon@...nwall.com>, Kees Cook <keescook@...omium.org>, Solar Designer <solar@...nwall.com>, WANG Cong <xiyou.wangcong@...il.com>, James Morris <james.l.morris@...cle.com>, Oleg Nesterov <oleg@...hat.com>, linux-security-module@...r.kernel.org, linux-fsdevel@...r.kernel.org, Alan Cox <alan@...rguk.ukuu.org.uk>, Greg KH <gregkh@...uxfoundation.org>, Ingo Molnar <mingo@...e.hu>, Stephen Wilson <wilsons@...rt.ca>, "Jason A. Donenfeld" <Jason@...c4.com> Subject: Re: [PATCH 8/9] proc: protect /proc/<pid>/{environ,pagemap} across execve On Sun, Mar 11, 2012 at 11:05:23AM +0300, Alexey Dobriyan wrote: > On Sun, Mar 11, 2012 at 12:25:18AM +0100, Djalal Harouni wrote: > > The /proc/<pid>/{environ,pagemap} are sensitive files which must be > > protected across execve to avoid information leaks. > > > > These files are protected by attaching them to their task at open time by > > saving the exec_id of the target task, this way in read we just compare > > the target task's exec_id and the previously saved exec_id of the > > proc_file_private struct, in other words we just bind these files to their > > appropriate process image at open time. We do this since we are able to do > > proper permission checks (ptrace) at each syscall, so we do not care about > > the reader. > > > > Another important rule is to set the exec_id of the target task before the > > permission checks at open, this way we do not race against target task > > execve, and it will be more effective if the exec_id check at read/write > > times are delayed as much as possible to be sure that the target task do > > not change during execve. > > > > This patch adds the open file_operation to the > > /proc/<pid>/{environ,pagemap} so we are able to set the exec_id of the > > target task and to do the appropriate permission checks. The exec_id check > > is done in the related read file_operation. > > ->open is duplicated. Right, I'll unify the code in a generic open function that does: * alloc and setup proc_file_private (which includes the exec_id) * ptrace check using mm_for_maps() unify only those who check PTRACE_MODE_READ * save priv_file_proc. This applies also to the release functions, I'll re-submit it. Thanks Alexey. -- tixxdz http://opendz.org
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