linux-kernel - [PATCH] mm/mmap: Fix leak on expand_downwards() and expand

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Message-ID: <20220512175915.1814885-1-Liam.Howlett@oracle.com>
Date:   Thu, 12 May 2022 17:59:25 +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:     Qian Cai <quic_qiancai@...cinc.com>
Subject: [PATCH] mm/mmap: Fix leak on expand_downwards() and expand_upwards()

A memory leak is possible in the race and error path in both
expand_downwards() and expand_upwards() due to the maple tree
preallocations.  Fix these by always destroying the maple state.

Fixes: a760774e7b7b (mm: start tracking VMAs with maple tree)
Signed-off-by: Liam R. Howlett <Liam.Howlett@...cle.com>
---
 mm/mmap.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/mm/mmap.c b/mm/mmap.c
index c147d2b5550b..ebfd71a79814 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -2047,6 +2047,7 @@ int expand_upwards(struct vm_area_struct *vma, unsigned long address)
 	}
 	anon_vma_unlock_write(vma->anon_vma);
 	khugepaged_enter_vma_merge(vma, vma->vm_flags);
+	mas_destroy(&mas);
 	return error;
 }
 #endif /* CONFIG_STACK_GROWSUP || CONFIG_IA64 */
@@ -2128,6 +2129,7 @@ int expand_downwards(struct vm_area_struct *vma, unsigned long address)
 	}
 	anon_vma_unlock_write(vma->anon_vma);
 	khugepaged_enter_vma_merge(vma, vma->vm_flags);
+	mas_destroy(&mas);
 	return error;
 }
 
-- 
2.35.1