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:
  mm_for_maps: take ->cred_guard_mutex to fix the race with exec
  mm_for_maps: shift down_read(mmap_sem) to the caller
  mm_for_maps: simplify, use ptrace_may_access()

3 files changed, 14 insertions, 15 deletions

diff --git a/fs/proc/base.c b/fs/proc/base.c
index 3ce5ae9e3d2d..175db258942f 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -234,23 +234,20 @@ static int check_mem_permission(struct task_struct *task)
 
 struct mm_struct *mm_for_maps(struct task_struct *task)
 {
-        struct mm_struct *mm = get_task_mm(task);
-        if (!mm)
+        struct mm_struct *mm;
+
+        if (mutex_lock_killable(&task->cred_guard_mutex))
                 return NULL;
-        down_read(&mm->mmap_sem);
-        task_lock(task);
-        if (task->mm != mm)
-                goto out;
-        if (task->mm != current->mm &&
-            __ptrace_may_access(task, PTRACE_MODE_READ) < 0)
-                goto out;
-        task_unlock(task);
+
+        mm = get_task_mm(task);
+        if (mm && mm != current->mm &&
+                        !ptrace_may_access(task, PTRACE_MODE_READ)) {
+                mmput(mm);
+                mm = NULL;
+        }
+        mutex_unlock(&task->cred_guard_mutex);
+
         return mm;
-out:
-        task_unlock(task);
-        up_read(&mm->mmap_sem);
-        mmput(mm);
-        return NULL;
 }
 
 static int proc_pid_cmdline(struct task_struct *task, char * buffer)
diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
index 6f61b7cc32e0..9bd8be1d235c 100644
--- a/fs/proc/task_mmu.c
+++ b/fs/proc/task_mmu.c
@@ -119,6 +119,7 @@ static void *m_start(struct seq_file *m, loff_t *pos)
         mm = mm_for_maps(priv->task);
         if (!mm)
                 return NULL;
+        down_read(&mm->mmap_sem);
 
         tail_vma = get_gate_vma(priv->task);
         priv->tail_vma = tail_vma;
diff --git a/fs/proc/task_nommu.c b/fs/proc/task_nommu.c
index 64a72e2e7650..8f5c05d3dbd3 100644
--- a/fs/proc/task_nommu.c
+++ b/fs/proc/task_nommu.c
@@ -189,6 +189,7 @@ static void *m_start(struct seq_file *m, loff_t *pos)
                 priv->task = NULL;
                 return NULL;
         }
+        down_read(&mm->mmap_sem);
 
         /* start from the Nth VMA */
         for (p = rb_first(&mm->mm_rb); p; p = rb_next(p))