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"); -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx"> email@xxxxxxxxx </a>