linux-kernel - [PATCH 3.14 57/79] pagemap: do not leak physical addresses to non-privileged userspace

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Date:	Tue, 24 Mar 2015 16:46:08 +0100
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	linux-kernel@...r.kernel.org
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	stable@...r.kernel.org,
	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
	Konstantin Khlebnikov <khlebnikov@...nvz.org>,
	Andy Lutomirski <luto@...capital.net>,
	Pavel Emelyanov <xemul@...allels.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Mark Seaborn <mseaborn@...omium.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>
Subject: [PATCH 3.14 57/79] pagemap: do not leak physical addresses to non-privileged userspace

3.14-stable review patch.  If anyone has any objections, please let me know.

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

From: "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>

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@...ux.intel.com>
Acked-by: Konstantin Khlebnikov <khlebnikov@...nvz.org>
Acked-by: Andy Lutomirski <luto@...capital.net>
Cc: Pavel Emelyanov <xemul@...allels.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>
Cc: Mark Seaborn <mseaborn@...omium.org>
Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 fs/proc/task_mmu.c |    3 +++
 1 file changed, 3 insertions(+)

--- a/fs/proc/task_mmu.c
+++ b/fs/proc/task_mmu.c
@@ -1227,6 +1227,9 @@ 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");

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