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

Author: torvalds

Documentation/filesystems/proc.txt

@@ -395,32 +395,6 @@ is not associated with a file:
 
  or if empty, the mapping is anonymous.
 
-The /proc/PID/task/TID/maps is a view of the virtual memory from the viewpoint
-of the individual tasks of a process. In this file you will see a mapping marked
-as [stack] if that task sees it as a stack. Hence, for the example above, the
-task-level map, i.e. /proc/PID/task/TID/maps for thread 1001 will look like this:
-
-08048000-08049000 r-xp 00000000 03:00 8312       /opt/test
-08049000-0804a000 rw-p 00001000 03:00 8312       /opt/test
-0804a000-0806b000 rw-p 00000000 00:00 0          [heap]
-a7cb1000-a7cb2000 ---p 00000000 00:00 0
-a7cb2000-a7eb2000 rw-p 00000000 00:00 0
-a7eb2000-a7eb3000 ---p 00000000 00:00 0
-a7eb3000-a7ed5000 rw-p 00000000 00:00 0          [stack]
-a7ed5000-a8008000 r-xp 00000000 03:00 4222       /lib/libc.so.6
-a8008000-a800a000 r--p 00133000 03:00 4222       /lib/libc.so.6
-a800a000-a800b000 rw-p 00135000 03:00 4222       /lib/libc.so.6
-a800b000-a800e000 rw-p 00000000 00:00 0
-a800e000-a8022000 r-xp 00000000 03:00 14462      /lib/libpthread.so.0
-a8022000-a8023000 r--p 00013000 03:00 14462      /lib/libpthread.so.0
-a8023000-a8024000 rw-p 00014000 03:00 14462      /lib/libpthread.so.0
-a8024000-a8027000 rw-p 00000000 00:00 0
-a8027000-a8043000 r-xp 00000000 03:00 8317       /lib/ld-linux.so.2
-a8043000-a8044000 r--p 0001b000 03:00 8317       /lib/ld-linux.so.2
-a8044000-a8045000 rw-p 0001c000 03:00 8317       /lib/ld-linux.so.2
-aff35000-aff4a000 rw-p 00000000 00:00 0
-ffffe000-fffff000 r-xp 00000000 00:00 0          [vdso]
-
 The /proc/PID/smaps is an extension based on maps, showing the memory
 consumption for each of the process's mappings. For each of mappings there
 is a series of lines such as the following:

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);

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");
 	}
 

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]");
 	}

include/linux/mm.h

@@ -1391,7 +1391,7 @@ static inline int stack_guard_page_end(struct vm_area_struct *vma,
 		!vma_growsup(vma->vm_next, addr);
 }
 
-int vma_is_stack_for_task(struct vm_area_struct *vma, struct task_struct *t);
+int vma_is_stack_for_current(struct vm_area_struct *vma);
 
 extern unsigned long move_page_tables(struct vm_area_struct *vma,
 		unsigned long old_addr, struct vm_area_struct *new_vma,

mm/mprotect.c

@@ -25,7 +25,6 @@
 #include <linux/perf_event.h>
 #include <linux/pkeys.h>
 #include <linux/ksm.h>
-#include <linux/pkeys.h>
 #include <asm/uaccess.h>
 #include <asm/pgtable.h>
 #include <asm/cacheflush.h>

mm/util.c

@@ -230,8 +230,10 @@ void __vma_link_list(struct mm_struct *mm, struct vm_area_struct *vma,
 }
 
 /* Check if the vma is being used as a stack by this task */
-int vma_is_stack_for_task(struct vm_area_struct *vma, struct task_struct *t)
+int vma_is_stack_for_current(struct vm_area_struct *vma)
 {
+	struct task_struct * __maybe_unused t = current;
+
 	return (vma->vm_start <= KSTK_ESP(t) && vma->vm_end >= KSTK_ESP(t));
 }
 

security/selinux/hooks.c

@@ -3557,7 +3557,7 @@ static int selinux_file_mprotect(struct vm_area_struct *vma,
 		} else if (!vma->vm_file &&
 			   ((vma->vm_start <= vma->vm_mm->start_stack &&
 			     vma->vm_end >= vma->vm_mm->start_stack) ||
-			    vma_is_stack_for_task(vma, current))) {
+			    vma_is_stack_for_current(vma))) {
 			rc = current_has_perm(current, PROCESS__EXECSTACK);
 		} else if (vma->vm_file && vma->anon_vma) {
 			/*