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]");
 	}