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
see http://lkml.org/lkml/2006/1/22/150)
- 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.
[akpm@linux-foundation.org: build fixes]
[akpm@linux-foundation.org: New sysctl numbers are old hat]
Signed-off-by: Kees Cook <kees@outflux.net>
Cc: Arjan van de Ven <arjan@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/CREDITS b/CREDITS
index c5f819b..e71fdce 100644
--- a/CREDITS
+++ b/CREDITS
@@ -661,7 +661,7 @@
E: kees@outflux.net
W: http://outflux.net/
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)
S: USA
diff --git a/Documentation/filesystems/proc.txt b/Documentation/filesystems/proc.txt
index 3f4b226..4f3e84c 100644
--- a/Documentation/filesystems/proc.txt
+++ b/Documentation/filesystems/proc.txt
@@ -1138,6 +1138,13 @@
Because the NMI watchdog shares registers with oprofile, by disabling the NMI
watchdog, oprofile may have more registers to utilize.
+maps_protect
+------------
+
+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
-----------------------------------------------
diff --git a/fs/proc/base.c b/fs/proc/base.c
index a721acf..17f7a7e 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -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 @@
NULL, &proc_info_file_operations, \
{ .proc_read = &proc_##OTYPE } )
+int maps_protect;
+EXPORT_SYMBOL(maps_protect);
+
static struct fs_struct *get_fs_struct(struct task_struct *task)
{
struct fs_struct *fs;
diff --git a/fs/proc/internal.h b/fs/proc/internal.h
index f771889..b215c35 100644
--- a/fs/proc/internal.h
+++ b/fs/proc/internal.h
@@ -37,6 +37,8 @@
extern int nommu_vma_show(struct seq_file *, struct vm_area_struct *);
#endif
+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 *);
diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
index 4008c06..c24d81a 100644
--- a/fs/proc/task_mmu.c
+++ b/fs/proc/task_mmu.c
@@ -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 @@
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 @@
#ifdef CONFIG_NUMA
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)
diff --git a/fs/proc/task_nommu.c b/fs/proc/task_nommu.c
index 7cddf6b..d8b8c71 100644
--- a/fs/proc/task_nommu.c
+++ b/fs/proc/task_nommu.c
@@ -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 @@
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);
}
diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index c904748..f0664bd 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -76,6 +76,7 @@
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 @@
.proc_handler = &proc_dointvec,
},
#endif
+#ifdef CONFIG_PROC_FS
+ {
+ .ctl_name = CTL_UNNUMBERED,
+ .procname = "maps_protect",
+ .data = &maps_protect,
+ .maxlen = sizeof(int),
+ .mode = 0644,
+ .proc_handler = &proc_dointvec,
+ },
+#endif
{ .ctl_name = 0 }
};
