From: Huang Ying <ying.huang@intel.com>
Subject: mm: /proc/pid/pagemap: hide swap entries from unprivileged users
Git-commit: ab6ecf247a9321e3180e021a6a60164dee53ab2e
Patch-mainline: v4.18-rc1
References: Git-fixes bsc#1109907

In commit ab676b7d6fbf ("pagemap: do not leak physical addresses to
non-privileged userspace"), the /proc/PID/pagemap is restricted to be
readable only by CAP_SYS_ADMIN to address some security issue.

In commit 1c90308e7a77 ("pagemap: hide physical addresses from
non-privileged users"), the restriction is relieved to make
/proc/PID/pagemap readable, but hide the physical addresses for
non-privileged users.

But the swap entries are readable for non-privileged users too.  This
has some security issues.  For example, for page under migrating, the
swap entry has physical address information.  So, in this patch, the
swap entries are hided for non-privileged users too.

[jeffm: dropped last two chunks; second chunk depends on 356515e7b64c2, third
 chunk depends on 88c28f2469151]

Link: http://lkml.kernel.org/r/20180508012745.7238-1-ying.huang@intel.com
Fixes: 1c90308e7a77 ("pagemap: hide physical addresses from non-privileged users")
Signed-off-by: "Huang, Ying" <ying.huang@intel.com>
Suggested-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Reviewed-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Reviewed-by: Konstantin Khlebnikov <khlebnikov@yandex-team.ru>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Konstantin Khlebnikov <khlebnikov@yandex-team.ru>
Cc: Andrei Vagin <avagin@openvz.org>
Cc: Jerome Glisse <jglisse@redhat.com>
Cc: Daniel Colascione <dancol@google.com>
Cc: Zi Yan <zi.yan@cs.rutgers.edu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Acked-by: Jeff Mahoney <jeffm@suse.com>
---
 fs/proc/task_mmu.c | 26 ++++++++++++++++----------
 1 file changed, 16 insertions(+), 10 deletions(-)

diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
index 7e074138d2f2..597969db9e90 100644
--- a/fs/proc/task_mmu.c
+++ b/fs/proc/task_mmu.c
@@ -1259,8 +1259,9 @@ static pagemap_entry_t pte_to_pagemap_entry(struct pagemapread *pm,
 		if (pte_swp_soft_dirty(pte))
 			flags |= PM_SOFT_DIRTY;
 		entry = pte_to_swp_entry(pte);
-		frame = swp_type(entry) |
-			(swp_offset(entry) << MAX_SWAPFILES_SHIFT);
+		if (pm->show_pfn)
+			frame = swp_type(entry) |
+				(swp_offset(entry) << MAX_SWAPFILES_SHIFT);
 		flags |= PM_SWAP;
 		if (is_migration_entry(entry))
 			page = migration_entry_to_page(entry);