| From: Konstantin Khlebnikov <khlebnikov@yandex-team.ru> |
| Date: Tue, 8 Sep 2015 15:00:07 -0700 |
| Subject: pagemap: hide physical addresses from non-privileged users |
| |
| commit 1c90308e7a77af6742a97d1021cca923b23b7f0d upstream. |
| |
| 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: ab676b7d6fbf ("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> |
| [bwh: Backported to 3.16: |
| - Add the same check in the places where we look up a PFN |
| - Adjust context] |
| Signed-off-by: Ben Hutchings <ben@decadent.org.uk> |
| --- |
| fs/proc/task_mmu.c | 25 ++++++++++++++----------- |
| 1 file changed, 14 insertions(+), 11 deletions(-) |
| |
| --- a/fs/proc/task_mmu.c |
| +++ b/fs/proc/task_mmu.c |
| @@ -862,6 +862,7 @@ 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) |
| @@ -921,12 +922,13 @@ static int pagemap_pte_hole(unsigned lon |
| 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)) |
| @@ -966,7 +968,7 @@ static void thp_pmd_to_pagemap_entry(pag |
| * This if-check is just to prepare for future implementation. |
| */ |
| if (pmd_present(pmd)) |
| - *pme = make_pme(PM_PFRAME(pmd_pfn(pmd) + offset) |
| + *pme = make_pme((pm->show_pfn ? PM_PFRAME(pmd_pfn(pmd) + offset) : 0) |
| | PM_STATUS2(pm->v2, pmd_flags2) | PM_PRESENT); |
| else |
| *pme = make_pme(PM_NOT_PRESENT(pm->v2) | PM_STATUS2(pm->v2, pmd_flags2)); |
| @@ -1075,7 +1077,7 @@ static void huge_pte_to_pagemap_entry(pa |
| pte_t pte, int offset, int flags2) |
| { |
| if (pte_present(pte)) |
| - *pme = make_pme(PM_PFRAME(pte_pfn(pte) + offset) | |
| + *pme = make_pme((pm->show_pfn ? PM_PFRAME(pte_pfn(pte) + offset) : 0) | |
| PM_STATUS2(pm->v2, flags2) | |
| PM_PRESENT); |
| else |
| @@ -1167,6 +1169,10 @@ static ssize_t pagemap_read(struct file |
| goto out_task; |
| |
| pm.v2 = soft_dirty_cleared; |
| + |
| + /* 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.buffer = kmalloc(pm.len * PM_ENTRY_BYTES, GFP_TEMPORARY); |
| ret = -ENOMEM; |
| @@ -1241,9 +1247,6 @@ 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"); |