linux-kernel - [PATCH -next] mm/nommu: fix error handling in split

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Date:   Wed, 24 Aug 2022 12:24:24 +0800
From:   Yang Yingliang <yangyingliang@...wei.com>
To:     <linux-kernel@...r.kernel.org>, <linux-mm@...ck.org>
CC:     <willy@...radead.org>, <akpm@...ux-foundation.org>,
        <Liam.Howlett@...cle.com>, <vbabka@...e.cz>
Subject: [PATCH -next] mm/nommu: fix error handling in split_vma()

The memory allocated before calling mas_preallocate() is leaked if it fails.
'mas' won't be modify until calling mas_preallocate(), so move it up and
add error label for free the memory.

Fixes: 8aff7dbeaeb1 ("nommu: remove uses of VMA linked list")
Signed-off-by: Yang Yingliang <yangyingliang@...wei.com>
---
 mm/nommu.c | 21 +++++++++++++--------
 1 file changed, 13 insertions(+), 8 deletions(-)

diff --git a/mm/nommu.c b/mm/nommu.c
index 6c611a689ec0..214c70e1d059 100644
--- a/mm/nommu.c
+++ b/mm/nommu.c
@@ -1355,9 +1355,13 @@ int split_vma(struct mm_struct *mm, struct vm_area_struct *vma,
 		return -ENOMEM;
 
 	new = vm_area_dup(vma);
-	if (!new) {
-		kmem_cache_free(vm_region_jar, region);
-		return -ENOMEM;
+	if (!new)
+		goto err_vma_dup;
+
+	if (mas_preallocate(&mas, vma, GFP_KERNEL)) {
+		pr_warn("Allocation of vma tree for process %d failed\n",
+			current->pid);
+		goto err_mas_preallocate;
 	}
 
 	/* most fields are the same, copy all, and then fixup */
@@ -1388,11 +1392,6 @@ int split_vma(struct mm_struct *mm, struct vm_area_struct *vma,
 	add_nommu_region(vma->vm_region);
 	add_nommu_region(new->vm_region);
 	up_write(&nommu_region_sem);
-	if (mas_preallocate(&mas, vma, GFP_KERNEL)) {
-		pr_warn("Allocation of vma tree for process %d failed\n",
-		       current->pid);
-		return -ENOMEM;
-	}
 
 	setup_vma_to_mm(vma, mm);
 	setup_vma_to_mm(new, mm);
@@ -1400,6 +1399,12 @@ int split_vma(struct mm_struct *mm, struct vm_area_struct *vma,
 	mas_store(&mas, vma);
 	vma_mas_store(new, &mas);
 	return 0;
+
+err_mas_preallocate:
+	vm_area_free(new);
+err_vma_dup:
+	kmem_cache_free(vm_region_jar, region);
+	return -ENOMEM;
 }
 
 /*
-- 
2.25.1