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pagemap: hide physical addresses from non-privileged users

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

See http://lkml.kernel.org/r/1425935472-17949-1-git-send-email-kirill@shutemov.name

Fixes: ab676b7d6f ("pagemap: do not leak physical addresses to non-privileged userspace")
Signed-off-by: Konstantin Khlebnikov <khlebnikov@yandex-team.ru>
Cc: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Reviewed-by: Mark Williamson <mwilliamson@undo-software.com>
Tested-by:  Mark Williamson <mwilliamson@undo-software.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Konstantin Khlebnikov 2015-09-08 15:00:07 -07:00 • committed by Linus Torvalds
parent 356515e7b6
commit 1c90308e7a
1 changed files with 14 additions and 11 deletions
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25
fs/proc/task_mmu.c
View file

@ -939,6 +939,7 @@ typedef struct {
struct pagemapread { struct pagemapread {
int pos, len; /* units: PM_ENTRY_BYTES, not bytes */ int pos, len; /* units: PM_ENTRY_BYTES, not bytes */
pagemap_entry_t *buffer; pagemap_entry_t *buffer;
bool show_pfn;
}; };
#define PAGEMAP_WALK_SIZE (PMD_SIZE) #define PAGEMAP_WALK_SIZE (PMD_SIZE)
@ -1015,7 +1016,8 @@ static pagemap_entry_t pte_to_pagemap_entry(struct pagemapread *pm,
struct page *page = NULL; struct page *page = NULL;
if (pte_present(pte)) { if (pte_present(pte)) {
frame = pte_pfn(pte); if (pm->show_pfn)
frame = pte_pfn(pte);
flags |= PM_PRESENT; flags |= PM_PRESENT;
page = vm_normal_page(vma, addr, pte); page = vm_normal_page(vma, addr, pte);
if (pte_soft_dirty(pte)) if (pte_soft_dirty(pte))
@ -1065,8 +1067,9 @@ static int pagemap_pmd_range(pmd_t *pmdp, unsigned long addr, unsigned long end,
*/ */
if (pmd_present(pmd)) { if (pmd_present(pmd)) {
flags |= PM_PRESENT; flags |= PM_PRESENT;
frame = pmd_pfn(pmd) + if (pm->show_pfn)
((addr & ~PMD_MASK) >> PAGE_SHIFT); frame = pmd_pfn(pmd) +
((addr & ~PMD_MASK) >> PAGE_SHIFT);
} }
for (; addr != end; addr += PAGE_SIZE) { for (; addr != end; addr += PAGE_SIZE) {
@ -1075,7 +1078,7 @@ static int pagemap_pmd_range(pmd_t *pmdp, unsigned long addr, unsigned long end,
err = add_to_pagemap(addr, &pme, pm); err = add_to_pagemap(addr, &pme, pm);
if (err) if (err)
break; break;
if (flags & PM_PRESENT) if (pm->show_pfn && (flags & PM_PRESENT))
frame++; frame++;
} }
spin_unlock(ptl); spin_unlock(ptl);
@ -1129,8 +1132,9 @@ static int pagemap_hugetlb_range(pte_t *ptep, unsigned long hmask,
flags |= PM_FILE; flags |= PM_FILE;
flags |= PM_PRESENT; flags |= PM_PRESENT;
frame = pte_pfn(pte) + if (pm->show_pfn)
((addr & ~hmask) >> PAGE_SHIFT); frame = pte_pfn(pte) +
((addr & ~hmask) >> PAGE_SHIFT);
} }
for (; addr != end; addr += PAGE_SIZE) { for (; addr != end; addr += PAGE_SIZE) {
@ -1139,7 +1143,7 @@ static int pagemap_hugetlb_range(pte_t *ptep, unsigned long hmask,
err = add_to_pagemap(addr, &pme, pm); err = add_to_pagemap(addr, &pme, pm);
if (err) if (err)
return err; return err;
if (flags & PM_PRESENT) if (pm->show_pfn && (flags & PM_PRESENT))
frame++; frame++;
} }
@ -1198,6 +1202,9 @@ static ssize_t pagemap_read(struct file *file, char __user *buf,
if (!count) if (!count)
goto out_mm; goto out_mm;
/* do not disclose physical addresses: attack vector */
pm.show_pfn = file_ns_capable(file, &init_user_ns, CAP_SYS_ADMIN);
pm.len = (PAGEMAP_WALK_SIZE >> PAGE_SHIFT); pm.len = (PAGEMAP_WALK_SIZE >> PAGE_SHIFT);
pm.buffer = kmalloc(pm.len * PM_ENTRY_BYTES, GFP_TEMPORARY); pm.buffer = kmalloc(pm.len * PM_ENTRY_BYTES, GFP_TEMPORARY);
ret = -ENOMEM; ret = -ENOMEM;
@ -1267,10 +1274,6 @@ static int pagemap_open(struct inode *inode, struct file *file)
{ {
struct mm_struct *mm; struct mm_struct *mm;
/* do not disclose physical addresses: attack vector */
if (!capable(CAP_SYS_ADMIN))
return -EPERM;
mm = proc_mem_open(inode, PTRACE_MODE_READ); mm = proc_mem_open(inode, PTRACE_MODE_READ);
if (IS_ERR(mm)) if (IS_ERR(mm))
return PTR_ERR(mm); return PTR_ERR(mm);