linux-kernel - [PATCH] mm/mmap: Fix vma_merge() offset when expanding the next vma

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Date:   Mon, 30 Jan 2023 14:57:13 -0500
From:   "Liam R. Howlett" <Liam.Howlett@...cle.com>
To:     maple-tree@...ts.infradead.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org,
        Andrew Morton <akpm@...ux-foundation.org>,
        linux-next@...r.kernel.org
Cc:     "Liam R. Howlett" <Liam.Howlett@...cle.com>,
        Sanan Hasanov <sanan.hasanov@...ghts.ucf.edu>,
        Matthew Wilcox <willy@...radead.org>,
        David Hildenbrand <david@...hat.com>,
        Hugh Dickins <hughd@...gle.com>
Subject: [PATCH] mm/mmap: Fix vma_merge() offset when expanding the next vma

The vm_pgoff was being set incorrectly when expanding the next VMA to a
lower address.  Fix the issue by using the mid->vm_pgoff value for this
merge case (aka case 8).  Note that this does not change case 3's
vm_pgoff as next and mid are the same VMA.

Reported-by: Sanan Hasanov <sanan.hasanov@...ghts.ucf.edu>
Link: https://lore.kernel.org/linux-mm/IA1PR07MB983017D2FBA174D2FF78CEB6ABCE9@IA1PR07MB9830.namprd07.prod.outlook.com/
Cc: Matthew Wilcox <willy@...radead.org>
Cc: David Hildenbrand <david@...hat.com>
Cc: Hugh Dickins <hughd@...gle.com>
Signed-off-by: Liam R. Howlett <Liam.Howlett@...cle.com>
---
 mm/mmap.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/mmap.c b/mm/mmap.c
index 00d90bbc250e..614ea2d93b0a 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -978,7 +978,7 @@ struct vm_area_struct *vma_merge(struct vma_iterator *vmi, struct mm_struct *mm,
 			vma = next;			/* case 3 */
 			vma_start = addr;
 			vma_end = next->vm_end;
-			vma_pgoff = next->vm_pgoff;
+			vma_pgoff = mid->vm_pgoff;
 			err = 0;
 			if (mid != next) {		/* case 8 */
 				remove = mid;
-- 
2.39.0