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

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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>
Cc: stable@vger.kernel.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Kirill A. Shutemov 2015-03-09 23:11:12 +02:00 committed by Linus Torvalds
parent 06e5801b8c
commit ab676b7d6f
1 changed files with 3 additions and 0 deletions
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3
fs/proc/task_mmu.c
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@ -1325,6 +1325,9 @@ static ssize_t pagemap_read(struct file *file, char __user *buf,
static int pagemap_open(struct inode *inode, struct file *file)
{
/* do not disclose physical addresses: attack vector */
if (!capable(CAP_SYS_ADMIN))
return -EPERM;
pr_warn_once("Bits 55-60 of /proc/PID/pagemap entries are about "
"to stop being page-shift some time soon. See the "
"linux/Documentation/vm/pagemap.txt for details.\n");