linux-kernel - [PATCH] mm/mmap: Fix do_brk_munmap() when munmapping multiple mappings

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Date:   Thu, 19 May 2022 15:05:22 +0000
From:   Liam Howlett <liam.howlett@...cle.com>
To:     "maple-tree@...ts.infradead.org" <maple-tree@...ts.infradead.org>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Andrew Morton <akpm@...ux-foundation.org>
Subject: [PATCH] mm/mmap: Fix do_brk_munmap() when munmapping multiple
 mappings

If the newbrk is less than the last brk vma start, then munmap entire
VMA(s).

Signed-off-by: Liam R. Howlett <Liam.Howlett@...cle.com>
---
 mm/mmap.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/mm/mmap.c b/mm/mmap.c
index f1fc9c5c068b..c065a3d9b5da 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -2942,8 +2942,7 @@ static int do_brk_munmap(struct ma_state *mas, struct vm_area_struct *vma,
 
 	arch_unmap(mm, newbrk, oldbrk);
 
-	if (likely((vma->vm_end < oldbrk) ||
-		   ((vma->vm_start == newbrk) && (vma->vm_end == oldbrk)))) {
+	if (likely((vma->vm_end < oldbrk) || (vma->vm_start >= newbrk))) {
 		/* remove entire mapping(s) */
 		ret = do_mas_align_munmap(mas, vma, mm, newbrk, oldbrk, uf,
 					  true);
-- 
2.35.1