+ mm-pagemap-hide-swap-entry-for-unprivileged-users.patch added to -mm tree

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The patch titled
     Subject: mm: /proc/pid/pagemap: hide swap entries from unprivileged users
has been added to the -mm tree.  Its filename is
     mm-pagemap-hide-swap-entry-for-unprivileged-users.patch

This patch should soon appear at
    http://ozlabs.org/~akpm/mmots/broken-out/mm-pagemap-hide-swap-entry-for-unprivileged-users.patch
and later at
    http://ozlabs.org/~akpm/mmotm/broken-out/mm-pagemap-hide-swap-entry-for-unprivileged-users.patch

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------------------------------------------------------
From: Huang Ying <ying.huang@xxxxxxxxx>
Subject: mm: /proc/pid/pagemap: hide swap entries from unprivileged users

In 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
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.

Link: http://lkml.kernel.org/r/20180508012745.7238-1-ying.huang@xxxxxxxxx
Fixes: 1c90308e7a77 ("pagemap: hide physical addresses from non-privileged users")
Signed-off-by: "Huang, Ying" <ying.huang@xxxxxxxxx>
Suggested-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
Reviewed-by: Naoya Horiguchi <n-horiguchi@xxxxxxxxxxxxx>
Reviewed-by: Konstantin Khlebnikov <khlebnikov@xxxxxxxxxxxxxx>
Cc: Konstantin Khlebnikov <khlebnikov@xxxxxxxxxxxxxx>
Cc: Andrei Vagin <avagin@xxxxxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxx>
Cc: Jerome Glisse <jglisse@xxxxxxxxxx>
Cc: Daniel Colascione <dancol@xxxxxxxxxx>
Cc: Zi Yan <zi.yan@xxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---

 fs/proc/task_mmu.c |   26 ++++++++++++++++----------
 1 file changed, 16 insertions(+), 10 deletions(-)

diff -puN fs/proc/task_mmu.c~mm-pagemap-hide-swap-entry-for-unprivileged-users fs/proc/task_mmu.c
--- a/fs/proc/task_mmu.c~mm-pagemap-hide-swap-entry-for-unprivileged-users
+++ a/fs/proc/task_mmu.c
@@ -1258,8 +1258,9 @@ static pagemap_entry_t pte_to_pagemap_en
 		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);
@@ -1310,11 +1311,14 @@ static int pagemap_pmd_range(pmd_t *pmdp
 #ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION
 		else if (is_swap_pmd(pmd)) {
 			swp_entry_t entry = pmd_to_swp_entry(pmd);
-			unsigned long offset = swp_offset(entry);
+			unsigned long offset;
 
-			offset += (addr & ~PMD_MASK) >> PAGE_SHIFT;
-			frame = swp_type(entry) |
-				(offset << MAX_SWAPFILES_SHIFT);
+			if (pm->show_pfn) {
+				offset = swp_offset(entry) +
+					((addr & ~PMD_MASK) >> PAGE_SHIFT);
+				frame = swp_type(entry) |
+					(offset << MAX_SWAPFILES_SHIFT);
+			}
 			flags |= PM_SWAP;
 			if (pmd_swp_soft_dirty(pmd))
 				flags |= PM_SOFT_DIRTY;
@@ -1332,10 +1336,12 @@ static int pagemap_pmd_range(pmd_t *pmdp
 			err = add_to_pagemap(addr, &pme, pm);
 			if (err)
 				break;
-			if (pm->show_pfn && (flags & PM_PRESENT))
-				frame++;
-			else if (flags & PM_SWAP)
-				frame += (1 << MAX_SWAPFILES_SHIFT);
+			if (pm->show_pfn) {
+				if (flags & PM_PRESENT)
+					frame++;
+				else if (flags & PM_SWAP)
+					frame += (1 << MAX_SWAPFILES_SHIFT);
+			}
 		}
 		spin_unlock(ptl);
 		return err;
_

Patches currently in -mm which might be from ying.huang@xxxxxxxxx are

mm-gup-prevent-pmd-checking-race-in-follow_pmd_mask.patch
mm-pagemap-hide-swap-entry-for-unprivileged-users.patch
mm-swap-fix-race-between-swapoff-and-some-swap-operations.patch
mm-swap-fix-race-between-swapoff-and-some-swap-operations-v6.patch
mm-fix-race-between-swapoff-and-mincore.patch

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