ANDROID: pagemap: do not leak physical addresses to non-privileged userspace

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 ]

We add this patch again for pass CTS
FileSystemPermissionTest: Assert /proc/self/pagemap not readable

Change-Id: Id4bf9ea27af000734356b921cd723868802b4335
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: Huang, Tao <huangtao@rock-chips.com>

diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
index 200e3b29aa22d535a37b17e1d51f194a68e21c1e..25d70a001c519c1ec48bebee9b6c501f92b64497 100644 (file)
--- a/fs/proc/task_mmu.c
+++ b/fs/proc/task_mmu.c
@@ -1396,6 +1396,16 @@ static int pagemap_open(struct inode *inode, struct file *file)
 {
        struct mm_struct *mm;
 
+#if defined(CONFIG_ARCH_ROCKCHIP) && defined(CONFIG_ANDROID)
+       /*
+        * For pass CTS
+        * FileSystemPermissionTest: Assert /proc/self/pagemap not readable
+        */
+       /* do not disclose physical addresses: attack vector */
+       if (!capable(CAP_SYS_ADMIN))
+               return -EPERM;
+#endif
+
        mm = proc_mem_open(inode, PTRACE_MODE_READ);
        if (IS_ERR(mm))
                return PTR_ERR(mm);