Re: [PATCH v4 4/5] pagemap: hide physical addresses from non-privileged users

Reviewed-by: Mark Williamson <redacted>

On Tue, Jul 21, 2015 at 9:39 AM, Konstantin Khlebnikov [off-list ref] wrote:

On Tue, Jul 21, 2015 at 11:11 AM, Naoya Horiguchi
[off-list ref] wrote:

quoted

On Tue, Jul 14, 2015 at 06:37:47PM +0300, Konstantin Khlebnikov wrote:

quoted

This patch makes pagemap readable for normal users and hides physical
addresses from them. For some use-cases PFN isn't required at all.

Signed-off-by: Konstantin Khlebnikov <redacted>
Fixes: ab676b7d6fbf ("pagemap: do not leak physical addresses to non-privileged userspace")
Link: http://lkml.kernel.org/r/1425935472-17949-1-git-send-email-kirill@shutemov.name
---
 fs/proc/task_mmu.c |   25 ++++++++++++++-----------
 1 file changed, 14 insertions(+), 11 deletions(-)

diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
index 040721fa405a..3a5d338ea219 100644
--- a/fs/proc/task_mmu.c
+++ b/fs/proc/task_mmu.c

@@ -937,6 +937,7 @@ typedef struct {
 struct pagemapread {
      int pos, len;           /* units: PM_ENTRY_BYTES, not bytes */
      pagemap_entry_t *buffer;
+     bool show_pfn;
 };

 #define PAGEMAP_WALK_SIZE    (PMD_SIZE)

@@ -1013,7 +1014,8 @@ static pagemap_entry_t pte_to_pagemap_entry(struct pagemapread *pm,
      struct page *page = NULL;

      if (pte_present(pte)) {
-             frame = pte_pfn(pte);
+             if (pm->show_pfn)
+                     frame = pte_pfn(pte);
              flags |= PM_PRESENT;
              page = vm_normal_page(vma, addr, pte);
              if (pte_soft_dirty(pte))

Don't you need the same if (pm->show_pfn) check in is_swap_pte path, too?
(although I don't think that it can be exploited by row hammer attack ...)

Yeah, but I see no reason for that.
Probably except swap on ramdrive, but this too weird =)

quoted

Thanks,
Naoya Horiguchi
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