report errors in /proc/*/*map* sanely

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

1 files changed, 5 insertions, 3 deletions

diff --git a/fs/proc/base.c b/fs/proc/base.c
index df73573e12c9..c28281102082 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -225,15 +225,17 @@ static int check_mem_permission(struct task_struct *task)
 struct mm_struct *mm_for_maps(struct task_struct *task)
 {
         struct mm_struct *mm;
+        int err;
 
-        if (mutex_lock_killable(&task->signal->cred_guard_mutex))
-                return NULL;
+        err =  mutex_lock_killable(&task->signal->cred_guard_mutex);
+        if (err)
+                return ERR_PTR(err);
 
         mm = get_task_mm(task);
         if (mm && mm != current->mm &&
                         !ptrace_may_access(task, PTRACE_MODE_READ)) {
                 mmput(mm);
-                mm = NULL;
+                mm = ERR_PTR(-EACCES);
         }
         mutex_unlock(&task->signal->cred_guard_mutex);