[PATCH] hfs: do not free node before using

From: Pan Bian <bianpan2016@163.com>
To: "Joe Perches" <joe@perches.com>,
	"Ernesto A. Fernández" <ernesto.mnd.fernandez@gmail.com>,
	"Andrew Morton" <akpm@linux-foundation.org>
Cc: linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org,
	Pan Bian <bianpan2016@163.com>
Subject: [PATCH] hfs: do not free node before using
Date: Fri, 23 Nov 2018 17:04:49 +0800	[thread overview]
Message-ID: <1542963889-128825-1-git-send-email-bianpan2016@163.com> (raw)

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.

Fixes: d614267329f("hfs/hfsplus: convert printks to pr_<level>")

Signed-off-by: Pan Bian <bianpan2016@163.com>
---
 fs/hfs/btree.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/fs/hfs/btree.c b/fs/hfs/btree.c
index 98b96ff..19017d2 100644
--- a/fs/hfs/btree.c
+++ b/fs/hfs/btree.c
@@ -338,13 +338,14 @@ 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


