[3.13.y-ckt stable] Patch "pagemap: do not leak physical addresses to non-privileged userspace" has been added to staging queue

[Kamal Mostafa]

This is a note to let you know that I have just added a patch titled

    pagemap: do not leak physical addresses to non-privileged userspace

to the linux-3.13.y-queue branch of the 3.13.y-ckt extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.13.y-queue

This patch is scheduled to be released in version 3.13.11-ckt19.

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.13.y-ckt tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Kamal

------

>From aa96296937d843e0f1484b27daa30758b70a383e Mon Sep 17 00:00:00 2001
From: "Kirill A. Shutemov" <kirill.shutemov at linux.intel.com>
Date: Mon, 9 Mar 2015 23:11:12 +0200
Subject: pagemap: do not leak physical addresses to non-privileged userspace

commit ab676b7d6fbf4b294bf198fb27ade5b0e865c7ce upstream.

As pointed by recent post[1] on exploiting DRAM physical imperfection,
/proc/PID/pagemap exposes sensitive information which can be used to do
attacks.

This disallows anybody without CAP_SYS_ADMIN to read the pagemap.

[1] http://googleprojectzero.blogspot.com/2015/03/exploiting-dram-rowhammer-bug-to-gain.html

[ Eventually we might want to do anything more finegrained, but for now
  this is the simple model.   - Linus ]

Signed-off-by: Kirill A. Shutemov <kirill.shutemov at linux.intel.com>
Acked-by: Konstantin Khlebnikov <khlebnikov at openvz.org>
Acked-by: Andy Lutomirski <luto at amacapital.net>
Cc: Pavel Emelyanov <xemul at parallels.com>
Cc: Andrew Morton <akpm at linux-foundation.org>
Cc: Mark Seaborn <mseaborn at chromium.org>
Signed-off-by: Linus Torvalds <torvalds at linux-foundation.org>
Signed-off-by: Kamal Mostafa <kamal at canonical.com>
---
 fs/proc/task_mmu.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
index 903c19f..b5f508d 100644
--- a/fs/proc/task_mmu.c
+++ b/fs/proc/task_mmu.c
@@ -1249,6 +1249,9 @@ out:

 static int pagemap_open(struct inode *inode, struct file *file)
 {
+	/* do not disclose physical addresses: attack vector */
+	if (!capable(CAP_SYS_ADMIN))
+		return -EPERM;
 	pr_warn_once("Bits 55-60 of /proc/PID/pagemap entries are about "
 			"to stop being page-shift some time soon. See the "
 			"linux/Documentation/vm/pagemap.txt for details.\n");
--
1.9.1