3.16.61-rc1 review patch. If anyone has any objections, please let me know. ------------------ From: Konstantin Khlebnikov <khlebnikov@xxxxxxxxxxxxxx> 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@xxxxxxxxxxxxx Fixes: ab676b7d6fbf ("pagemap: do not leak physical addresses to non-privileged userspace") Signed-off-by: Konstantin Khlebnikov <khlebnikov@xxxxxxxxxxxxxx> Cc: Naoya Horiguchi <n-horiguchi@xxxxxxxxxxxxx> Reviewed-by: Mark Williamson <mwilliamson@xxxxxxxxxxxxxxxxx> Tested-by: Mark Williamson <mwilliamson@xxxxxxxxxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> [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@xxxxxxxxxxxxxxx> --- 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");
