From: Oleg Nesterov <oleg@redhat.com>
To: Jann Horn <jann@thejh.net>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>,
Roland McGrath <roland@hack.frob.com>,
John Johansen <john.johansen@canonical.com>,
James Morris <james.l.morris@oracle.com>,
"Serge E. Hallyn" <serge@hallyn.com>,
Paul Moore <aul@paul-moore.com>,
Stephen Smalley <sds@tycho.nsa.gov>,
Eric Paris <eparis@parisplace.org>,
Casey Schaufler <casey@schaufler-ca.com>,
Kees Cook <keescook@chromium.org>,
Andrew Morton <akpm@linux-foundation.org>,
Janis Danisevskis <jdanis@google.com>,
Seth Forshee <seth.forshee@canonical.com>,
"Eric . Biederman" <ebiederm@xmission.com>,
Thomas Gleixner <tglx@linutronix.de>,
Benjamin LaHaise <bcrl@kvack.org>,
Ben Hutchings <ben@decadent.org.uk>,
Andy Lutomirski <luto@amacapital.net>,
Linus Torvalds <torvalds@linux-foundation.org>,
linux-fsdevel@vger.kernel.org,
linux-security-module@vger.kernel.org, security@kernel.org
Subject: Re: [PATCH v2 1/8] exec: introduce cred_guard_light
Date: Fri, 30 Sep 2016 17:35:05 +0200 [thread overview]
Message-ID: <20160930153505.GA17573@redhat.com> (raw)
In-Reply-To: <1474663238-22134-2-git-send-email-jann@thejh.net>
On 09/23, Jann Horn wrote:
>
> This is a new per-threadgroup lock that can often be taken instead of
> cred_guard_mutex and has less deadlock potential.
Oh, please don't.
> I'm doing this because
> Oleg Nesterov mentioned the potential for deadlocks, in particular if a
> debugged task is stuck in execve, trying to get rid of a ptrace-stopped
> thread, and the debugger attempts to inspect procfs files of the debugged
> task.
Yes, but we need to fix this anyway. And I am not sure the new mutex can
actually help.
And I think that cred_guard_mutex is already over-used in fs/proc. Say,
I think lock_trace() must die, I simply can't understand why it is useful.
Suppose we modify, say, proc_pid_stack() to do
save_stack_trace_tsk(task, &trace);
if (!ptrace_may_access(task, ...))
goto return -EPERM;
for (i = 0; i < trace.nr_entries; i++)
seq_printf(...);
return 0;
is there any problem if it shows some trace before setuid exec does
install_exec_creds() ?
Oleg.
next prev parent reply other threads:[~2016-09-30 15:36 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-09-23 20:40 [PATCH v2 0/8] Various fixes related to ptrace_may_access() Jann Horn
2016-09-23 20:40 ` [PATCH v2 1/8] exec: introduce cred_guard_light Jann Horn
2016-09-30 15:35 ` Oleg Nesterov [this message]
2016-09-30 18:27 ` Eric W. Biederman
2016-10-03 16:02 ` Oleg Nesterov
2016-10-30 21:12 ` Jann Horn
2016-09-23 20:40 ` [PATCH v2 2/8] exec: turn self_exec_id into self_privunit Jann Horn
2016-09-23 21:04 ` Andy Lutomirski
2016-09-23 21:33 ` Jann Horn
2016-09-30 13:20 ` Oleg Nesterov
2016-09-30 13:44 ` Oleg Nesterov
2016-09-30 18:30 ` Kees Cook
2016-09-30 18:59 ` Jann Horn
2016-09-30 19:05 ` Kees Cook
2016-10-03 16:37 ` Oleg Nesterov
2016-09-23 20:40 ` [PATCH v2 3/8] proc: use open()-time creds for ptrace checks Jann Horn
2016-09-23 20:40 ` [PATCH v2 4/8] futex: don't leak robust_list pointer Jann Horn
2016-09-30 14:52 ` Oleg Nesterov
2016-10-30 17:16 ` Jann Horn
2016-11-02 21:39 ` Jann Horn
2016-11-02 22:47 ` Jann Horn
2016-09-23 20:40 ` [PATCH v2 5/8] proc: lock properly in ptrace_may_access callers Jann Horn
2016-09-23 20:40 ` [PATCH v2 6/8] ptrace: warn on ptrace_may_access without proper locking Jann Horn
2016-09-23 20:40 ` [PATCH v2 7/8] fs/proc: fix attr access check Jann Horn
2016-09-23 20:40 ` [PATCH v2 8/8] Documentation: add security/ptrace_checks.txt Jann Horn
2016-10-02 3:16 ` Krister Johansen
2016-10-30 19:09 ` Jann Horn
2016-10-31 4:14 ` Eric W. Biederman
2016-10-31 13:39 ` Jann Horn
2016-11-03 20:43 ` Krister Johansen
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