Merge branch 'mm-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull vmap stack fixes from Ingo Molnar:
 "This is fallout from CONFIG_HAVE_ARCH_VMAP_STACK=y on x86: stack
  accesses that used to be just somewhat questionable are now totally
  buggy.

  These changes try to do it without breaking the ABI: the fields are
  left there, they are just reporting zero, or reporting narrower
  information (the maps file change)"

* 'mm-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  mm: Change vm_is_stack_for_task() to vm_is_stack_for_current()
  fs/proc: Stop trying to report thread stacks
  fs/proc: Stop reporting eip and esp in /proc/PID/stat
  mm/numa: Remove duplicated include from mprotect.c

3 files changed, 25 insertions, 41 deletions

diff --git a/fs/proc/array.c b/fs/proc/array.c
index 89600fd5963d..81818adb8e9e 100644
--- a/fs/proc/array.c
+++ b/fs/proc/array.c
@@ -412,10 +412,11 @@ static int do_task_stat(struct seq_file *m, struct pid_namespace *ns,
         mm = get_task_mm(task);
         if (mm) {
                 vsize = task_vsize(mm);
-                if (permitted) {
-                        eip = KSTK_EIP(task);
-                        esp = KSTK_ESP(task);
-                }
+                /*
+                 * esp and eip are intentionally zeroed out.  There is no
+                 * non-racy way to read them without freezing the task.
+                 * Programs that need reliable values can use ptrace(2).
+                 */
         }
 
         get_task_comm(tcomm, task);
diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
index 6909582ce5e5..35b92d81692f 100644
--- a/fs/proc/task_mmu.c
+++ b/fs/proc/task_mmu.c
@@ -266,24 +266,15 @@ static int do_maps_open(struct inode *inode, struct file *file,
  * /proc/PID/maps that is the stack of the main task.
  */
 static int is_stack(struct proc_maps_private *priv,
-                    struct vm_area_struct *vma, int is_pid)
+                    struct vm_area_struct *vma)
 {
-        int stack = 0;
-
-        if (is_pid) {
-                stack = vma->vm_start <= vma->vm_mm->start_stack &&
-                        vma->vm_end >= vma->vm_mm->start_stack;
-        } else {
-                struct inode *inode = priv->inode;
-                struct task_struct *task;
-
-                rcu_read_lock();
-                task = pid_task(proc_pid(inode), PIDTYPE_PID);
-                if (task)
-                        stack = vma_is_stack_for_task(vma, task);
-                rcu_read_unlock();
-        }
-        return stack;
+        /*
+         * We make no effort to guess what a given thread considers to be
+         * its "stack".  It's not even well-defined for programs written
+         * languages like Go.
+         */
+        return vma->vm_start <= vma->vm_mm->start_stack &&
+                vma->vm_end >= vma->vm_mm->start_stack;
 }
 
 static void
@@ -354,7 +345,7 @@ show_map_vma(struct seq_file *m, struct vm_area_struct *vma, int is_pid)
                         goto done;
                 }
 
-                if (is_stack(priv, vma, is_pid))
+                if (is_stack(priv, vma))
                         name = "[stack]";
         }
 
@@ -1669,7 +1660,7 @@ static int show_numa_map(struct seq_file *m, void *v, int is_pid)
                 seq_file_path(m, file, "\n\t= ");
         } else if (vma->vm_start <= mm->brk && vma->vm_end >= mm->start_brk) {
                 seq_puts(m, " heap");
-        } else if (is_stack(proc_priv, vma, is_pid)) {
+        } else if (is_stack(proc_priv, vma)) {
                 seq_puts(m, " stack");
         }
 
diff --git a/fs/proc/task_nommu.c b/fs/proc/task_nommu.c
index faacb0c0d857..37175621e890 100644
--- a/fs/proc/task_nommu.c
+++ b/fs/proc/task_nommu.c
@@ -124,25 +124,17 @@ unsigned long task_statm(struct mm_struct *mm,
 }
 
 static int is_stack(struct proc_maps_private *priv,
-                    struct vm_area_struct *vma, int is_pid)
+                    struct vm_area_struct *vma)
 {
         struct mm_struct *mm = vma->vm_mm;
-        int stack = 0;
-
-        if (is_pid) {
-                stack = vma->vm_start <= mm->start_stack &&
-                        vma->vm_end >= mm->start_stack;
-        } else {
-                struct inode *inode = priv->inode;
-                struct task_struct *task;
-
-                rcu_read_lock();
-                task = pid_task(proc_pid(inode), PIDTYPE_PID);
-                if (task)
-                        stack = vma_is_stack_for_task(vma, task);
-                rcu_read_unlock();
-        }
-        return stack;
+
+        /*
+         * We make no effort to guess what a given thread considers to be
+         * its "stack".  It's not even well-defined for programs written
+         * languages like Go.
+         */
+        return vma->vm_start <= mm->start_stack &&
+                vma->vm_end >= mm->start_stack;
 }
 
 /*
@@ -184,7 +176,7 @@ static int nommu_vma_show(struct seq_file *m, struct vm_area_struct *vma,
         if (file) {
                 seq_pad(m, ' ');
                 seq_file_path(m, file, "");
-        } else if (mm && is_stack(priv, vma, is_pid)) {
+        } else if (mm && is_stack(priv, vma)) {
                 seq_pad(m, ' ');
                 seq_printf(m, "[stack]");
         }