linux-kernel - [PATCH 1/1] hfsplus: do not free node before using

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Date:   Sat, 24 Nov 2018 17:57:21 +0800
From:   Pan Bian <bianpan2016@....com>
To:     Andrew Morton <akpm@...ux-foundation.org>,
        ernesto.mnd.fernandez@...il.com
Cc:     linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
        Pan Bian <bianpan2016@....com>
Subject: [PATCH 1/1] hfsplus: do not free node before using

The function hfs_bmap_free frees node via hfs_bnode_put(node).
However, it then reads node->this when dumping error message on an error
path, which may result in a use-after-free bug. This patch frees node
only when it is never used.

Signed-off-by: Pan Bian <bianpan2016@....com>
---
 fs/hfsplus/btree.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/fs/hfsplus/btree.c b/fs/hfsplus/btree.c
index 236efe5..66774f4 100644
--- a/fs/hfsplus/btree.c
+++ b/fs/hfsplus/btree.c
@@ -466,14 +466,15 @@ void hfs_bmap_free(struct hfs_bnode *node)
 
 		nidx -= len * 8;
 		i = node->next;
-		hfs_bnode_put(node);
 		if (!i) {
 			/* panic */;
 			pr_crit("unable to free bnode %u. "
 					"bmap not found!\n",
 				node->this);
+			hfs_bnode_put(node);
 			return;
 		}
+		hfs_bnode_put(node);
 		node = hfs_bnode_find(tree, i);
 		if (IS_ERR(node))
 			return;
-- 
2.7.4