This patch makes pagemap readable for normal users back but hides physical
addresses from them. For some use cases PFN isn't required at all: flags
give information about presence, page type (anon/file/swap), soft-dirty mark,
and hint about page mapcount state: exclusive(mapcount = 1) or (mapcount > 1).
Signed-off-by: Konstantin Khlebnikov <khlebnikov@xxxxxxxxxxxxxx>
Fixes: ab676b7d6fbf ("pagemap: do not leak physical addresses to non-privileged userspace")
Link: lkml.kernel.org/r/1425935472-17949-1-git-send-email-kirill@xxxxxxxxxxxxx
---
fs/proc/task_mmu.c | 36 ++++++++++++++++++++++--------------
1 file changed, 22 insertions(+), 14 deletions(-)
diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
index 29febec65de4..0b7a8ffec95f 100644
--- a/fs/proc/task_mmu.c
+++ b/fs/proc/task_mmu.c
@@ -962,6 +962,7 @@ struct pagemapread {
int pos, len; /* units: PM_ENTRY_BYTES, not bytes */
pagemap_entry_t *buffer;
bool v2;
+ bool show_pfn;
};
#define PAGEMAP_WALK_SIZE (PMD_SIZE)
@@ -1046,12 +1047,13 @@ out:
static void pte_to_pagemap_entry(pagemap_entry_t *pme, struct pagemapread *pm,
struct vm_area_struct *vma, unsigned long addr, pte_t pte)
{
- u64 frame, flags;
+ u64 frame = 0, flags;
struct page *page = NULL;
int flags2 = 0;
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))
@@ -1087,15 +1089,19 @@ static void pte_to_pagemap_entry(pagemap_entry_t *pme, struct pagemapread *pm,
static void thp_pmd_to_pagemap_entry(pagemap_entry_t *pme, struct pagemapread *pm,
pmd_t pmd, int offset, int pmd_flags2)
{
+ u64 frame = 0;
+
/*
* Currently pmd for thp is always present because thp can not be
* swapped-out, migrated, or HWPOISONed (split in such cases instead.)
* This if-check is just to prepare for future implementation.
*/
- if (pmd_present(pmd))
- *pme = make_pme(PM_PFRAME(pmd_pfn(pmd) + offset)
- | PM_STATUS2(pm->v2, pmd_flags2) | PM_PRESENT);
- else
+ if (pmd_present(pmd)) {
+ if (pm->show_pfn)
+ frame = pmd_pfn(pmd) + offset;
+ *pme = make_pme(PM_PFRAME(frame) | PM_PRESENT |
+ PM_STATUS2(pm->v2, pmd_flags2));
+ } else
*pme = make_pme(PM_NOT_PRESENT(pm->v2) | PM_STATUS2(pm->v2, pmd_flags2));
}
#else
@@ -1171,11 +1177,14 @@ static int pagemap_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end,
static void huge_pte_to_pagemap_entry(pagemap_entry_t *pme, struct pagemapread *pm,
pte_t pte, int offset, int flags2)
{
- if (pte_present(pte))
- *pme = make_pme(PM_PFRAME(pte_pfn(pte) + offset) |
- PM_STATUS2(pm->v2, flags2) |
- PM_PRESENT);
- else
+ u64 frame = 0;
+
+ if (pte_present(pte)) {
+ if (pm->show_pfn)
+ frame = pte_pfn(pte) + offset;
+ *pme = make_pme(PM_PFRAME(frame) | PM_PRESENT |
+ PM_STATUS2(pm->v2, flags2));
+ } else
*pme = make_pme(PM_NOT_PRESENT(pm->v2) |
PM_STATUS2(pm->v2, flags2));
}
@@ -1260,6 +1269,8 @@ static ssize_t pagemap_read(struct file *file, char __user *buf,
if (!count)
goto out_task;
+ /* do not disclose physical addresses: attack vector */
+ pm.show_pfn = capable(CAP_SYS_ADMIN);
pm.v2 = soft_dirty_cleared;
pm.len = (PAGEMAP_WALK_SIZE >> PAGE_SHIFT);
pm.buffer = kmalloc(pm.len * PM_ENTRY_BYTES, GFP_TEMPORARY);
@@ -1335,9 +1346,6 @@ out:
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");
--
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