From efd4149342db2df41b1bbe68972ead853b30e444 Mon Sep 17 00:00:00 2001 From: Peter Xu Date: Fri, 5 Aug 2022 12:00:03 -0400 Subject: mm/smaps: don't access young/dirty bit if pte unpresent These bits should only be valid when the ptes are present. Introducing two booleans for it and set it to false when !pte_present() for both pte and pmd accountings. The bug is found during code reading and no real world issue reported, but logically such an error can cause incorrect readings for either smaps or smaps_rollup output on quite a few fields. For example, it could cause over-estimate on values like Shared_Dirty, Private_Dirty, Referenced. Or it could also cause under-estimate on values like LazyFree, Shared_Clean, Private_Clean. Link: https://lkml.kernel.org/r/20220805160003.58929-1-peterx@redhat.com Fixes: b1d4d9e0cbd0 ("proc/smaps: carefully handle migration entries") Fixes: c94b6923fa0a ("/proc/PID/smaps: Add PMD migration entry parsing") Signed-off-by: Peter Xu Reviewed-by: Vlastimil Babka Reviewed-by: David Hildenbrand Reviewed-by: Yang Shi Cc: Konstantin Khlebnikov Cc: Huang Ying Signed-off-by: Andrew Morton --- fs/proc/task_mmu.c | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-) (limited to 'fs/proc/task_mmu.c') diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c index a3398d0f1927..4e0023643f8b 100644 --- a/fs/proc/task_mmu.c +++ b/fs/proc/task_mmu.c @@ -527,10 +527,12 @@ static void smaps_pte_entry(pte_t *pte, unsigned long addr, struct vm_area_struct *vma = walk->vma; bool locked = !!(vma->vm_flags & VM_LOCKED); struct page *page = NULL; - bool migration = false; + bool migration = false, young = false, dirty = false; if (pte_present(*pte)) { page = vm_normal_page(vma, addr, *pte); + young = pte_young(*pte); + dirty = pte_dirty(*pte); } else if (is_swap_pte(*pte)) { swp_entry_t swpent = pte_to_swp_entry(*pte); @@ -560,8 +562,7 @@ static void smaps_pte_entry(pte_t *pte, unsigned long addr, if (!page) return; - smaps_account(mss, page, false, pte_young(*pte), pte_dirty(*pte), - locked, migration); + smaps_account(mss, page, false, young, dirty, locked, migration); } #ifdef CONFIG_TRANSPARENT_HUGEPAGE -- cgit v1.2.3