[PATCH] mm: arm64: Fix the out-of-bounds issue in contpte_clear_young_dirty_ptes

[Barry Song]

From: Barry Song <v-songbaohua at oppo.com>

We are passing a huge nr to __clear_young_dirty_ptes() right
now. While we should pass the number of pages, we are actually
passing CONT_PTE_SIZE. This is causing lots of crashes of
MADV_FREE, panic oops could vary everytime.

Fixes: 89e86854fb0a ("mm/arm64: override clear_young_dirty_ptes() batch helper")
Cc: Lance Yang <ioworker0 at gmail.com>
Cc: Barry Song <21cnbao at gmail.com>
Cc: Ryan Roberts <ryan.roberts at arm.com>
Cc: David Hildenbrand <david at redhat.com>
Cc: Jeff Xie <xiehuan09 at gmail.com>
Cc: Kefeng Wang <wangkefeng.wang at huawei.com>
Cc: Michal Hocko <mhocko at suse.com>
Cc: Minchan Kim <minchan at kernel.org>
Cc: Muchun Song <songmuchun at bytedance.com>
Cc: Peter Xu <peterx at redhat.com>
Cc: Yang Shi <shy828301 at gmail.com>
Cc: Yin Fengwei <fengwei.yin at intel.com>
Cc: Zach O'Keefe <zokeefe at google.com>
Cc: Catalin Marinas <catalin.marinas at arm.com>
Cc: Will Deacon <will at kernel.org>
Signed-off-by: Barry Song <v-songbaohua at oppo.com>
---
 arch/arm64/mm/contpte.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/arm64/mm/contpte.c b/arch/arm64/mm/contpte.c
index 9f9486de0004..a3edced29ac1 100644
--- a/arch/arm64/mm/contpte.c
+++ b/arch/arm64/mm/contpte.c
@@ -376,7 +376,7 @@ void contpte_clear_young_dirty_ptes(struct vm_area_struct *vma,
 	 * clearing access/dirty for the whole block.
 	 */
 	unsigned long start = addr;
-	unsigned long end = start + nr;
+	unsigned long end = start + nr * PAGE_SIZE;
 
 	if (pte_cont(__ptep_get(ptep + nr - 1)))
 		end = ALIGN(end, CONT_PTE_SIZE);
@@ -386,7 +386,7 @@ void contpte_clear_young_dirty_ptes(struct vm_area_struct *vma,
 		ptep = contpte_align_down(ptep);
 	}
 
-	__clear_young_dirty_ptes(vma, start, ptep, end - start, flags);
+	__clear_young_dirty_ptes(vma, start, ptep, (end - start) / PAGE_SIZE, flags);
 }
 EXPORT_SYMBOL_GPL(contpte_clear_young_dirty_ptes);
 
-- 
2.34.1