linux-kernel - [PATCH] mm: arm64: Fix the out-of-bounds issue in contpte_clear_young_dirty

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Date: Fri, 24 May 2024 12:54:44 +1200
From: Barry Song <21cnbao@...il.com>
To: akpm@...ux-foundation.org,
	linux-mm@...ck.org
Cc: linux-arm-kernel@...ts.infradead.org,
	linux-kernel@...r.kernel.org,
	Barry Song <v-songbaohua@...o.com>,
	Lance Yang <ioworker0@...il.com>,
	Barry Song <21cnbao@...il.com>,
	Ryan Roberts <ryan.roberts@....com>,
	David Hildenbrand <david@...hat.com>,
	Jeff Xie <xiehuan09@...il.com>,
	Kefeng Wang <wangkefeng.wang@...wei.com>,
	Michal Hocko <mhocko@...e.com>,
	Minchan Kim <minchan@...nel.org>,
	Muchun Song <songmuchun@...edance.com>,
	Peter Xu <peterx@...hat.com>,
	Yang Shi <shy828301@...il.com>,
	Yin Fengwei <fengwei.yin@...el.com>,
	Zach O'Keefe <zokeefe@...gle.com>,
	Catalin Marinas <catalin.marinas@....com>,
	Will Deacon <will@...nel.org>
Subject: [PATCH] mm: arm64: Fix the out-of-bounds issue in contpte_clear_young_dirty_ptes

From: Barry Song <v-songbaohua@...o.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@...il.com>
Cc: Barry Song <21cnbao@...il.com>
Cc: Ryan Roberts <ryan.roberts@....com>
Cc: David Hildenbrand <david@...hat.com>
Cc: Jeff Xie <xiehuan09@...il.com>
Cc: Kefeng Wang <wangkefeng.wang@...wei.com>
Cc: Michal Hocko <mhocko@...e.com>
Cc: Minchan Kim <minchan@...nel.org>
Cc: Muchun Song <songmuchun@...edance.com>
Cc: Peter Xu <peterx@...hat.com>
Cc: Yang Shi <shy828301@...il.com>
Cc: Yin Fengwei <fengwei.yin@...el.com>
Cc: Zach O'Keefe <zokeefe@...gle.com>
Cc: Catalin Marinas <catalin.marinas@....com>
Cc: Will Deacon <will@...nel.org>
Signed-off-by: Barry Song <v-songbaohua@...o.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