linux-kernel - [PATCH] mm/mmap: Fix potential leak on do_mas_align

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Date:   Fri, 13 May 2022 14:15:53 +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 potential leak on do_mas_align_munmap()

There is a leak when the system is low on resources and fails to
allocate enough memory to complete the munmap task.  Fix this by adding
the necessary free operations in the unwinding.

Fixes: a760774e7b7b (mm: start tracking VMAs with maple tree)
Signed-off-by: Liam R. Howlett <Liam.Howlett@...cle.com>
---
 mm/mmap.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/mm/mmap.c b/mm/mmap.c
index ebfd71a79814..9d41df730b22 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -2365,7 +2365,7 @@ do_mas_align_munmap(struct ma_state *mas, struct vm_area_struct *vma,
 		return -ENOMEM;
 
 	if (mas_preallocate(&mas_detach, vma, GFP_KERNEL))
-		return -ENOMEM;
+		goto detach_alloc_fail;
 
 	mas->last = end - 1;
 	/*
@@ -2504,6 +2504,8 @@ do_mas_align_munmap(struct ma_state *mas, struct vm_area_struct *vma,
 map_count_exceeded:
 split_failed:
 userfaultfd_error:
+	mas_destroy(&mas_detach);
+detach_alloc_fail:
 	mas_destroy(mas);
 	return error;
 }
-- 
2.35.1