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>
Acked-by: Michal Hocko <mhocko@xxxxxxxx>
Cc: Konstantin Khlebnikov <khlebnikov@xxxxxxxxxxxxxx>
Cc: Andrei Vagin <avagin@xxxxxxxxxx>
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
@@ -1259,8 +1259,9 @@ 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);
@@ -1311,11 +1312,14 @@ 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;
@@ -1333,10 +1337,12 @@ 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;
_
--
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