linux-kernel - [PATCH] mm/smaps: Don't access young/dirty bit if pte unpresent

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Date:   Wed,  3 Aug 2022 18:03:29 -0400
From:   Peter Xu <peterx@...hat.com>
To:     linux-kernel@...r.kernel.org, linux-mm@...ck.org
Cc:     peterx@...hat.com, Yang Shi <shy828301@...il.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Nadav Amit <nadav.amit@...il.com>,
        David Hildenbrand <david@...hat.com>,
        Konstantin Khlebnikov <khlebnikov@...nvz.org>
Subject: [PATCH] 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().

Cc: Konstantin Khlebnikov <khlebnikov@...nvz.org>
Fixes: b1d4d9e0cbd0 ("proc/smaps: carefully handle migration entries", 2012-05-31)
Signed-off-by: Peter Xu <peterx@...hat.com>
---
 fs/proc/task_mmu.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
index 9913f3be9fd2..482f91577f8c 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
-- 
2.32.0