Date: Wed, 2 Oct 2013 15:37:59 +0100 From: Djalal Harouni <tixxdz@...ndz.org> To: Andy Lutomirski <luto@...capital.net> Cc: "Eric W. Biederman" <ebiederm@...ssion.com>, Kees Cook <keescook@...omium.org>, Al Viro <viro@...iv.linux.org.uk>, Andrew Morton <akpm@...ux-foundation.org>, Linus Torvalds <torvalds@...ux-foundation.org>, Ingo Molnar <mingo@...nel.org>, "Serge E. Hallyn" <serge.hallyn@...ntu.com>, Cyrill Gorcunov <gorcunov@...nvz.org>, David Rientjes <rientjes@...gle.com>, LKML <linux-kernel@...r.kernel.org>, linux-fsdevel@...r.kernel.org, kernel-hardening@...ts.openwall.com, tixxdz@...il.com Subject: Re: [PATCH v2 0/9] procfs: protect /proc/<pid>/* files with file->f_cred On Tue, Oct 01, 2013 at 06:40:41PM -0700, Andy Lutomirski wrote: > On 10/01/2013 01:26 PM, Djalal Harouni wrote: > > /proc/<pid>/* entries varies at runtime, appropriate permission checks > > need to happen during each system call. > > > > Currently some of these sensitive entries are protected by performing > > the ptrace_may_access() check. However even with that the /proc file > > descriptors can be passed to a more privileged process > > (e.g. a suid-exec) which will pass the classic ptrace_may_access() > > check. In general the ->open() call will be issued by an unprivileged > > process while the ->read(),->write() calls by a more privileged one. > > > > Example of these files are: > > /proc/*/syscall, /proc/*/stack etc. > > > > And any open(/proc/self/*) then suid-exec to read()/write() /proc/self/* > > > > > > These files are protected during read() by the ptrace_may_access(), > > however the file descriptor can be passed to a suid-exec which can be > > used to read data and bypass ASLR. Of course this was discussed several > > times on LKML. > > Can you elaborate on what it is that you're fixing? That is, can you > give a concrete example of what process opens what file and passes the > fd to what process? Yes, the references were already given in this email: https://lkml.org/lkml/2013/8/31/209 This has been discussed several times on lkml: https://lkml.org/lkml/2013/8/28/544 https://lkml.org/lkml/2013/8/28/564 (check Kees's references) > I'm having trouble following your description. Process open a /proc file and pass the fd to a more privilaged process that will pass the ptrace_may_access() check, while the original process that opened that file should fail at the ptrace_may_access() > --Andy > -- Djalal Harouni http://opendz.org
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