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From: Jann Horn <jann@thejh.net>
To: Alexander Viro <viro@zeniv.linux.org.uk>,
	Roland McGrath <roland@hack.frob.com>,
	Oleg Nesterov <oleg@redhat.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>
Cc: linux-fsdevel@vger.kernel.org,
	linux-security-module@vger.kernel.org, security@kernel.org
Subject: [PATCH v2 6/8] ptrace: warn on ptrace_may_access without proper locking
Date: Fri, 23 Sep 2016 22:40:36 +0200	[thread overview]
Message-ID: <1474663238-22134-7-git-send-email-jann@thejh.net> (raw)
In-Reply-To: <1474663238-22134-1-git-send-email-jann@thejh.net>

If neither of those locks is taken during a ptrace_may_access() call, that
is a strong indicator for a security bug where post-execve process
properties can be leaked by racing with execve().

Signed-off-by: Jann Horn <jann@thejh.net>
---
 kernel/ptrace.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/kernel/ptrace.c b/kernel/ptrace.c
index 29ace11..17c2245 100644
--- a/kernel/ptrace.c
+++ b/kernel/ptrace.c
@@ -225,6 +225,9 @@ static int __ptrace_may_access(struct task_struct *task, unsigned int mode,
 	kuid_t caller_uid;
 	kgid_t caller_gid;
 
+	WARN_ON(!mutex_is_locked(&task->signal->cred_guard_mutex) &&
+		!mutex_is_locked(&task->signal->cred_guard_light));
+
 	if (!(mode & PTRACE_MODE_FSCREDS) == !(mode & PTRACE_MODE_REALCREDS)) {
 		WARN(1, "denying ptrace access check without PTRACE_MODE_*CREDS\n");
 		return -EPERM;
-- 
2.1.4


  parent reply	other threads:[~2016-09-23 20:40 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
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 ` Jann Horn [this message]
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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