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@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>
Signed-off-by: mancha security <mancha1@zoho.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
index 65fc60a07c47ba7fb13879f130c4c9c93046c18f..9f285fb9bab392e1342a4e0c45333a80ded284ea 100644 (file)
--- a/fs/proc/task_mmu.c
+++ b/fs/proc/task_mmu.c
@@ -1110,9 +1110,19 @@ 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 */