[PATCH 3.2 135/221] pagemap: do not leak physical addresses to non-privileged userspace

Ben Hutchings
2015-05-05T02:07:32Z

From: "Kirill A. Shutemov" <kirill.shutemov@linux.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@linux.intel.com>
Acked-by: Konstantin Khlebnikov <khlebnikov@openvz.org>
Acked-by: Andy Lutomirski <luto@amacapital.net>
Cc: Pavel Emelyanov <xemul@parallels.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Mark Seaborn <mseaborn@chromium.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
[mancha security: Backported to 3.10]
Signed-off-by: mancha security <mancha1@zoho.com>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
fs/proc/task_mmu.c | 10 ++++++++++
1 file changed, 10 insertions(+)

--- a/fs/proc/task_mmu.c
+++ b/fs/proc/task_mmu.c
@@ -864,9 +864,19 @@ 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 */