Commit 5096add8 authored by Kees Cook's avatar Kees Cook Committed by Linus Torvalds

proc: maps protection

The /proc/pid/ "maps", "smaps", and "numa_maps" files contain sensitive
information about the memory location and usage of processes.  Issues:

- maps should not be world-readable, especially if programs expect any
  kind of ASLR protection from local attackers.
- maps cannot just be 0400 because "-D_FORTIFY_SOURCE=2 -O2" makes glibc
  check the maps when %n is in a *printf call, and a setuid(getuid())
  process wouldn't be able to read its own maps file.  (For reference
- a system-wide toggle is needed to allow prior behavior in the case of
  non-root applications that depend on access to the maps contents.

This change implements a check using "ptrace_may_attach" before allowing
access to read the maps contents.  To control this protection, the new knob
/proc/sys/kernel/maps_protect has been added, with corresponding updates to
the procfs documentation.

[ build fixes]
[ New sysctl numbers are old hat]
Signed-off-by: default avatarKees Cook <>
Cc: Arjan van de Ven <>
Signed-off-by: default avatarAndrew Morton <>
Signed-off-by: default avatarLinus Torvalds <>
parent 4a1ccb5b
......@@ -661,7 +661,7 @@ N: Kees Cook
P: 1024D/17063E6D 9FA3 C49C 23C9 D1BC 2E30 1975 1FFF 4BA9 1706 3E6D
D: Minor updates to SCSI code for the Communications type
D: Minor updates to SCSI types, added /proc/pid/maps protection
S: (ask for current address)
......@@ -1138,6 +1138,13 @@ determine whether or not they are still functioning properly.
Because the NMI watchdog shares registers with oprofile, by disabling the NMI
watchdog, oprofile may have more registers to utilize.
Enables/Disables the protection of the per-process proc entries "maps" and
"smaps". When enabled, the contents of these files are visible only to
readers that are allowed to ptrace() the given process.
2.4 /proc/sys/vm - The virtual memory subsystem
......@@ -64,6 +64,7 @@
#include <linux/smp_lock.h>
#include <linux/rcupdate.h>
#include <linux/kallsyms.h>
#include <linux/module.h>
#include <linux/mount.h>
#include <linux/security.h>
#include <linux/ptrace.h>
......@@ -123,6 +124,9 @@ struct pid_entry {
NULL, &proc_info_file_operations, \
{ .proc_read = &proc_##OTYPE } )
int maps_protect;
static struct fs_struct *get_fs_struct(struct task_struct *task)
struct fs_struct *fs;
......@@ -37,6 +37,8 @@ do { \
extern int nommu_vma_show(struct seq_file *, struct vm_area_struct *);
extern int maps_protect;
extern void create_seq_entry(char *name, mode_t mode, const struct file_operations *f);
extern int proc_exe_link(struct inode *, struct dentry **, struct vfsmount **);
extern int proc_tid_stat(struct task_struct *, char *);
......@@ -3,6 +3,7 @@
#include <linux/mount.h>
#include <linux/seq_file.h>
#include <linux/highmem.h>
#include <linux/ptrace.h>
#include <linux/pagemap.h>
#include <linux/mempolicy.h>
......@@ -142,6 +143,9 @@ static int show_map_internal(struct seq_file *m, void *v, struct mem_size_stats
dev_t dev = 0;
int len;
if (maps_protect && !ptrace_may_attach(task))
return -EACCES;
if (file) {
struct inode *inode = vma->vm_file->f_path.dentry->d_inode;
dev = inode->i_sb->s_dev;
......@@ -512,11 +516,22 @@ const struct file_operations proc_maps_operations = {
extern int show_numa_map(struct seq_file *m, void *v);
static int show_numa_map_checked(struct seq_file *m, void *v)
struct proc_maps_private *priv = m->private;
struct task_struct *task = priv->task;
if (maps_protect && !ptrace_may_attach(task))
return -EACCES;
return show_numa_map(m, v);
static struct seq_operations proc_pid_numa_maps_op = {
.start = m_start,
.next = m_next,
.stop = m_stop,
.show = show_numa_map
.show = show_numa_map_checked
static int numa_maps_open(struct inode *inode, struct file *file)
......@@ -2,6 +2,7 @@
#include <linux/mm.h>
#include <linux/file.h>
#include <linux/mount.h>
#include <linux/ptrace.h>
#include <linux/seq_file.h>
#include "internal.h"
......@@ -143,6 +144,12 @@ out:
static int show_map(struct seq_file *m, void *_vml)
struct vm_list_struct *vml = _vml;
struct proc_maps_private *priv = m->private;
struct task_struct *task = priv->task;
if (maps_protect && !ptrace_may_attach(task))
return -EACCES;
return nommu_vma_show(m, vml->vma);
......@@ -76,6 +76,7 @@ extern int pid_max_min, pid_max_max;
extern int sysctl_drop_caches;
extern int percpu_pagelist_fraction;
extern int compat_log;
extern int maps_protect;
/* this is needed for the proc_dointvec_minmax for [fs_]overflow UID and GID */
static int maxolduid = 65535;
......@@ -603,6 +604,16 @@ static ctl_table kern_table[] = {
.proc_handler = &proc_dointvec,
.ctl_name = CTL_UNNUMBERED,
.procname = "maps_protect",
.data = &maps_protect,
.maxlen = sizeof(int),
.mode = 0644,
.proc_handler = &proc_dointvec,
{ .ctl_name = 0 }
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