mm-smaps-dont-access-young-dirty-bit-if-pte-unpresent.patch removed from -mm tree

The quilt patch titled
Subject: mm/smaps: don't access young/dirty bit if pte unpresent
has been removed from the -mm tree. Its filename was
mm-smaps-dont-access-young-dirty-bit-if-pte-unpresent.patch

This patch was dropped because it was merged into the mm-hotfixes-stable branch of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

------------------------------------------------------
From: Peter Xu <[email protected]>
Subject: mm/smaps: don't access young/dirty bit if pte unpresent
Date: Fri, 5 Aug 2022 12:00:03 -0400

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.

---

 fs/proc/task_mmu.c |    7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

@@ -527,10 +527,12 @@ static void smaps_pte_entry(pte_t *pte,
 	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,
 	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

_

Patches currently in -mm which might be from [email protected] are

mm-x86-use-swp_type_bits-in-3-level-swap-macros.patch mm-swap-comment-all-the-ifdef-in-swapopsh.patch mm-swap-add-swp_offset_pfn-to-fetch-pfn-from-swap-entry.patch mm-thp-carry-over-dirty-bit-when-thp-splits-on-pmd.patch mm-remember-young-dirty-bit-for-page-migrations.patch mm-swap-cache-maximum-swapfile-size-when-init-swap.patch mm-swap-cache-swap-migration-a-d-bits-support.patch