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: cb07099feb52 ("proc/smaps: carefully handle migration entries")
Fixes: 25cd809f0f06 ("/proc/PID/smaps: Add PMD migration entry parsing")
Signed-off-by: Peter Xu <peterx@redhat.com>
Reviewed-by: Vlastimil Babka <vbabka@suse.cz>
Reviewed-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Yang Shi <shy828301@gmail.com>
Cc: Konstantin Khlebnikov <khlebnikov@openvz.org>
Cc: Huang Ying <ying.huang@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
index a3398d0f1927f5461b0888fafefa9b02479e7546..4e0023643f8be9f90ba9612e4b57a54af39ecd25 100644 (file)
--- 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