linux-kernel - [PATCH] mm/mmap: Fix copy_vma() new

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Date:   Wed, 6 Jul 2022 00:35:33 +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>
CC:     Yu Zhao <yuzhao@...gle.com>
Subject: [PATCH] mm/mmap: Fix copy_vma() new_vma check

When checking new_vma limits to ensure they are not within where the
copy of the vma will be placed, ensure new_vma is not NULL.

Fixes: ded0cf440d9b (mm: remove the vma linked list)
Reported-by: Yu Zhao <yuzhao@...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 dacc01b0126a..9eb663cde5c7 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -3293,7 +3293,7 @@ struct vm_area_struct *copy_vma(struct vm_area_struct **vmap,
 	}
 
 	new_vma = find_vma_prev(mm, addr, &prev);
-	if (new_vma->vm_start < addr + len)
+	if (new_vma && new_vma->vm_start < addr + len)
 		return NULL;	/* should never get here */
 
 	new_vma = vma_merge(mm, prev, addr, addr + len, vma->vm_flags,
-- 
2.35.1