From ca3fde5214e1d24f78269b337d3f22afd6bf445e Mon Sep 17 00:00:00 2001
From: Jann Horn <jannh@google.com>
Date: Sat Sep 29 03:49:26 2018 +0200
Subject: [PATCH] apparmor: don't try to replace stale label in ptraceme check
Git-commit: ca3fde5214e1d24f78269b337d3f22afd6bf445e
References: git-fixes
Patch-mainline: v4.20-rc1

begin_current_label_crit_section() must run in sleepable context because
when label_is_stale() is true, aa_replace_current_label() runs, which uses
prepare_creds(), which can sleep.

Until now, the ptraceme access check (which runs with tasklist_lock held)
violated this rule.

Fixes: b2d09ae449ced ("apparmor: move ptrace checks to using labels")
Reported-by: Cyrill Gorcunov <gorcunov@gmail.com>
Reported-by: kernel test robot <rong.a.chen@intel.com>
Signed-off-by: Jann Horn <jannh@google.com>
Signed-off-by: John Johansen <john.johansen@canonical.com>
Acked-by: Goldwyn Rodrigues <rgoldwyn@suse.com>

diff --git a/security/apparmor/lsm.c b/security/apparmor/lsm.c
index 2c842f2..d08aac0 100644

--- a/security/apparmor/lsm.c
+++ b/security/apparmor/lsm.c
@@ -132,11 +132,11 @@ static int apparmor_ptrace_traceme(struct task_struct *parent)
 	struct aa_label *tracer, *tracee;
 	int error;
 
-	tracee = begin_current_label_crit_section();
+	tracee = __begin_current_label_crit_section();
 	tracer = aa_get_task_label(parent);
 	error = aa_may_ptrace(tracer, tracee, AA_PTRACE_TRACE);
 	aa_put_label(tracer);
-	end_current_label_crit_section(tracee);
+	__end_current_label_crit_section(tracee);
 
 	return error;
 }