Donate to e Foundation | Murena handsets with /e/OS | Own a part of Murena! Learn more

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

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: default avatarKees Cook <kees@outflux.net>
Cc: Arjan van de Ven <arjan@infradead.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 4a1ccb5b

CREDITS

+1 −1
Original line number Diff line number Diff line
@@ -661,7 +661,7 @@ N: Kees Cook 
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

Documentation/filesystems/proc.txt

+7 −0
Original line number Diff line number Diff line
@@ -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.



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

-----------------------------------------------

fs/proc/base.c

+4 −0
Original line number Diff line number Diff line
@@ -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;

EXPORT_SYMBOL(maps_protect);



static struct fs_struct *get_fs_struct(struct task_struct *task)

{

	struct fs_struct *fs;

fs/proc/internal.h

+2 −0
Original line number Diff line number Diff line
@@ -37,6 +37,8 @@ do { \ 
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 *);

fs/proc/task_mmu.c

+16 −1
Original line number Diff line number Diff line
@@ -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 = { 
#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)