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Message-Id: <20230929183041.2835469-4-Liam.Howlett@oracle.com>
Date: Fri, 29 Sep 2023 14:30:41 -0400
From: "Liam R. Howlett" <Liam.Howlett@...cle.com>
To: Andrew Morton <akpm@...ux-foundation.org>
Cc: linux-mm@...ck.org, linux-kernel@...r.kernel.org,
Jann Horn <jannh@...gle.com>,
Lorenzo Stoakes <lstoakes@...il.com>,
Vlastimil Babka <vbabka@...e.cz>,
Suren Baghdasaryan <surenb@...gle.com>,
Matthew Wilcox <willy@...radead.org>,
"Liam R. Howlett" <Liam.Howlett@...cle.com>
Subject: [PATCH v3 3/3] mmap: Add clarifying comment to vma_merge() code
When tracing through the code in vma_merge(), it was not completely
clear why the error return to a dup_anon_vma() call would not overwrite
a previous attempt to the same function. This commit adds a comment
specifying why it is safe.
Suggested-by: Jann Horn <jannh@...gle.com>
Link: https://lore.kernel.org/linux-mm/CAG48ez3iDwFPR=Ed1BfrNuyUJPMK_=StjxhUsCkL6po1s7bONg@mail.gmail.com/
Signed-off-by: Liam R. Howlett <Liam.Howlett@...cle.com>
---
mm/mmap.c | 5 +++++
1 file changed, 5 insertions(+)
diff --git a/mm/mmap.c b/mm/mmap.c
index f9f0a5fe4db4..9967acbd070f 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -943,6 +943,11 @@ struct vm_area_struct *vma_merge(struct vma_iterator *vmi, struct mm_struct *mm,
vma_start_write(curr);
remove = curr;
remove2 = next;
+ /*
+ * Note that the dup_anon_vma below cannot overwrite err
+ * since the first caller would do nothing unless next
+ * has an anon_vma.
+ */
if (!next->anon_vma)
err = dup_anon_vma(prev, curr, &anon_dup);
}
--
2.40.1
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