From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail202.messagelabs.com (mail202.messagelabs.com [216.82.254.227]) by kanga.kvack.org (Postfix) with SMTP id 4086D8D0001 for ; Tue, 2 Nov 2010 07:34:19 -0400 (EDT) Message-ID: <4CCFF1BA.1010206@redhat.com> Date: Tue, 02 Nov 2010 07:10:50 -0400 From: Avi Kivity MIME-Version: 1.0 Subject: Re: [RFC][PATCH] Cross Memory Attach References: <20100915104855.41de3ebf@lilo> <4C90A6C7.9050607@redhat.com> <20100916104819.36d10acb@lilo> <4C91E2CC.9040709@redhat.com> <20101102140710.5f2a6557@lilo> In-Reply-To: <20101102140710.5f2a6557@lilo> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org To: Christopher Yeoh Cc: Bryan Donlan , linux-kernel@vger.kernel.org, Linux Memory Management List , Ingo Molnar List-ID: On 11/01/2010 11:37 PM, Christopher Yeoh wrote: > > > > You could have each process open /proc/self/mem and pass the fd using > > SCM_RIGHTS. > > > > That eliminates a race; with copy_to_process(), by the time the pid > > is looked up it might designate a different process. > > Just to revive an old thread (I've been on holidays), but this doesn't > work either. the ptrace check is done by mem_read (eg on each read) so > even if you do pass the fd using SCM_RIGHTS, reads on the fd still > fail. > > So unless there's good reason to believe that the ptrace permission > check is no longer needed, the /proc/pid/mem interface doesn't seem to > be an option for what we want to do. > Perhaps move the check to open(). I can understand the desire to avoid letting random processes peek each other's memory, but once a process has opened its own /proc/self/mem and explicitly passed it to another, we should allow it. -- I have a truly marvellous patch that fixes the bug which this signature is too narrow to contain. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom policy in Canada: sign http://dissolvethecrtc.ca/ Don't email: email@kvack.org