pagemap: do not leak physical addresses to non-privileged userspace
Kirill A. Shutemov [Mon, 7 Dec 2015 23:24:08 +0000 (15:24 -0800)]
[ Upstream commit ab676b7d6fbf4b294bf198fb27ade5b0e865c7ce ]

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 ]

bug 200160374

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>
Cc: stable@vger.kernel.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Sasha Levin <sasha.levin@oracle.com>
Change-Id: I85acefa5c77fcd26d4fde436c37870d41bb8062e
Signed-off-by: Krishna Reddy <vdumpa@nvidia.com>
Reviewed-on: http://git-master/r/842648
Reviewed-by: Robert Shih <rshih@nvidia.com>
Tested-by: Robert Shih <rshih@nvidia.com>

fs/proc/task_mmu.c

index 154ebf8..f80c936 100644 (file)
@@ -1187,9 +1187,18 @@ out:
        return ret;
 }
 
+static int pagemap_open(struct inode *inode, struct file *file)
+{
+       /* do not disclose physical addresses: 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 */