Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jmorris/security-testing-2.6

* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jmorris/security-testing-2.6: (105 commits)
  SELinux: don't check permissions for kernel mounts
  security: pass mount flags to security_sb_kern_mount()
  SELinux: correctly detect proc filesystems of the form "proc/foo"
  Audit: Log TIOCSTI
  user namespaces: document CFS behavior
  user namespaces: require cap_set{ug}id for CLONE_NEWUSER
  user namespaces: let user_ns be cloned with fairsched
  CRED: fix sparse warnings
  User namespaces: use the current_user_ns() macro
  User namespaces: set of cleanups (v2)
  nfsctl: add headers for credentials
  coda: fix creds reference
  capabilities: define get_vfs_caps_from_disk when file caps are not enabled
  CRED: Allow kernel services to override LSM settings for task actions
  CRED: Add a kernel_service object class to SELinux
  CRED: Differentiate objective and effective subjective credentials on a task
  CRED: Documentation
  CRED: Use creds in file structs
  CRED: Prettify commoncap.c
  CRED: Make execve() take advantage of copy-on-write credentials
  ...

2 files changed, 46 insertions, 1 deletions

diff --git a/lib/Makefile b/lib/Makefile
index 7cb65d85aeb..80fe8a3ec12 100644
--- a/lib/Makefile
+++ b/lib/Makefile
@@ -11,7 +11,7 @@ lib-y := ctype.o string.o vsprintf.o cmdline.o \
 	 rbtree.o radix-tree.o dump_stack.o \
 	 idr.o int_sqrt.o extable.o prio_tree.o \
 	 sha1.o irq_regs.o reciprocal_div.o argv_split.o \
-	 proportions.o prio_heap.o ratelimit.o show_mem.o
+	 proportions.o prio_heap.o ratelimit.o show_mem.o is_single_threaded.o
 
 lib-$(CONFIG_MMU) += ioremap.o
 lib-$(CONFIG_SMP) += cpumask.o
diff --git a/lib/is_single_threaded.c b/lib/is_single_threaded.c
new file mode 100644
index 00000000000..f1ed2fe76c6
--- /dev/null
+++ b/lib/is_single_threaded.c
@@ -0,0 +1,45 @@
+/* Function to determine if a thread group is single threaded or not
+ *
+ * Copyright (C) 2008 Red Hat, Inc. All Rights Reserved.
+ * Written by David Howells (dhowells@redhat.com)
+ * - Derived from security/selinux/hooks.c
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public Licence
+ * as published by the Free Software Foundation; either version
+ * 2 of the Licence, or (at your option) any later version.
+ */
+
+#include <linux/sched.h>
+
+/**
+ * is_single_threaded - Determine if a thread group is single-threaded or not
+ * @p: A task in the thread group in question
+ *
+ * This returns true if the thread group to which a task belongs is single
+ * threaded, false if it is not.
+ */
+bool is_single_threaded(struct task_struct *p)
+{
+	struct task_struct *g, *t;
+	struct mm_struct *mm = p->mm;
+
+	if (atomic_read(&p->signal->count) != 1)
+		goto no;
+
+	if (atomic_read(&p->mm->mm_users) != 1) {
+		read_lock(&tasklist_lock);
+		do_each_thread(g, t) {
+			if (t->mm == mm && t != p)
+				goto no_unlock;
+		} while_each_thread(g, t);
+		read_unlock(&tasklist_lock);
+	}
+
+	return true;
+
+no_unlock:
+	read_unlock(&tasklist_lock);
+no:
+	return false;
+}