linux-kernel - [PATCH] mm/mmap: Fix return on maple tree expand fail in brk()

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Message-ID: <20220712145059.4191132-1-Liam.Howlett@oracle.com>
Date:   Tue, 12 Jul 2022 14:51:08 +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>,
        Hugh Dickins <hughd@...gle.com>
Subject: [PATCH] mm/mmap: Fix return on maple tree expand fail in brk()

When do_brk_flags() fails, ensure the necessary locking is undone.

Fixes: e9bad648fe05 (mm/mmap: change do_brk_flags() to expand existing VMA and add do_brk_munmap())
Suggested-by: Hugh Dickins <hughd@...gle.com>
Signed-off-by: Liam R. Howlett <Liam.Howlett@...cle.com>
---
 mm/mmap.c | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/mm/mmap.c b/mm/mmap.c
index 9a07bc18e6aa..f25f53d7600d 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -3071,7 +3071,7 @@ static int do_brk_flags(struct ma_state *mas, struct vm_area_struct *vma,
 		vma->vm_end = addr + len;
 		vma->vm_flags |= VM_SOFTDIRTY;
 		if (mas_store_gfp(mas, vma, GFP_KERNEL))
-			return -ENOMEM;
+			goto mas_expand_failed;
 
 		if (vma->anon_vma) {
 			anon_vma_interval_tree_post_update_vma(vma);
@@ -3113,6 +3113,13 @@ static int do_brk_flags(struct ma_state *mas, struct vm_area_struct *vma,
 vma_alloc_fail:
 	vm_unacct_memory(len >> PAGE_SHIFT);
 	return -ENOMEM;
+
+mas_expand_failed:
+	if (vma->anon_vma) {
+		anon_vma_interval_tree_post_update_vma(vma);
+		anon_vma_unlock_write(vma->anon_vma);
+	}
+	return -ENOMEM;
 }
 
 int vm_brk_flags(unsigned long addr, unsigned long request, unsigned long flags)
-- 
2.35.1