From mboxrd@z Thu Jan 1 00:00:00 1970 From: Davidlohr Bueso Subject: Re: [PATCH -next v2 0/4] mm: replace mmap_sem for mm->exe_file serialization Date: Sun, 15 Mar 2015 10:34:23 -0700 Message-ID: <1426440863.28068.103.camel@stgolabs.net> References: <1426372766-3029-1-git-send-email-dave@stgolabs.net> <20150315142137.GA21741@redhat.com> <1426431270.28068.92.camel@stgolabs.net> <20150315152652.GA24590@redhat.com> <1426434125.28068.100.camel@stgolabs.net> <20150315170521.GA2278@moon> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20150315170521.GA2278@moon> Sender: linux-api-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Cyrill Gorcunov Cc: Oleg Nesterov , akpm-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org, viro-RmSDqhL/yNMiFSDQTTA3OLVCufUGDwFn@public.gmane.org, koct9i-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org, linux-mm-Bw31MaZKKs3YtjvyW6yDsg@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Kees Cook , "Michael Kerrisk (man-pages)" , Linux API List-Id: linux-api@vger.kernel.org On Sun, 2015-03-15 at 20:05 +0300, Cyrill Gorcunov wrote: > On Sun, Mar 15, 2015 at 08:42:05AM -0700, Davidlohr Bueso wrote: > > > > > Yes, this code needs cleanups, I agree. Does this series makes it better? > > > > > To me it doesn't, and the diffstat below shows that it blows the code. > > > > > > > > Looking at some of the caller paths now, I have to disagree. > > > > > > And I believe you are wrong. But let me repeat, I leave this to Cyrill > > > and Konstantin. Cleanups are always subjective. > > > > > > > > In fact, to me it complicates this code. For example. Personally I think > > > > > that MMF_EXE_FILE_CHANGED should die. And currently we can just remove it. > > > > > > > > How could you remove this? > > > > > > Just remove this flag and the test_and_set_bit(MMF_EXE_FILE_CHANGED) check. > > > Again, this is subjective, but to me it looks ugly. Why do we allow to > > > change ->exe_file but only once? > > This came from very first versions of the functionality implemented > in prctl. It supposed to help sysadmins to notice if there exe > transition happened. As to me it doesn't bring much security, if I > would be a virus I would simply replace executing code with ptrace > or via other ways without telling outside world that i've changed > exe path. That said I would happily rip off this MMF_EXE_FILE_CHANGED > bit but I fear security guys won't be that happy about it. > (CC'ing Kees) Also adding Michael for any prctl manpage and api changes.