linux-kernel - [ 43/48] pagemap: do not leak physical addresses to non-privileged userspace

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Date:	Fri, 15 May 2015 10:06:13 +0200
From:	Willy Tarreau <w@....eu>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:	"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>,
	mancha security <mancha1@...o.com>,
	Ben Hutchings <ben@...adent.org.uk>, Willy Tarreau <w@....eu>
Subject: [ 43/48] pagemap: do not leak physical addresses to
 non-privileged userspace

2.6.32-longterm 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>
[mancha security: Backported to 3.10]
Signed-off-by: mancha security <mancha1@...o.com>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
(cherry picked from commit 1ffc3cd9a36b504c20ce98fe5eeb5463f389e1ac)

Signed-off-by: Willy Tarreau <w@....eu>
---
 fs/proc/task_mmu.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
index 3b7b82a..73db5a6 100644
--- a/fs/proc/task_mmu.c
+++ b/fs/proc/task_mmu.c
@@ -773,9 +773,19 @@ out:
 	return ret;
 }

+static int pagemap_open(struct inode *inode, struct file *file)
+{
+	/* do not disclose physical addresses to unprivileged
+	   userspace (closes a rowhammer attack vector) */
+	if (!capable(CAP_SYS_ADMIN))
+		return -EPERM;
+	return 0;
+}
+
 const struct file_operations proc_pagemap_operations = {
 	.llseek		= mem_lseek, /* borrow this */
 	.read		= pagemap_read,
+	.open		= pagemap_open,
 };
 #endif /* CONFIG_PROC_PAGE_MONITOR */

-- 
1.7.12.2.21.g234cd45.dirty

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