linux-kernel - [PATCH AUTOSEL 4.9 43/45] hfsplus: do not free node before using

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Message-Id: <20181205094706.7225-43-sashal@kernel.org>
Date:   Wed,  5 Dec 2018 04:47:04 -0500
From:   Sasha Levin <sashal@...nel.org>
To:     stable@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:     Pan Bian <bianpan2016@....com>,
        "Ernesto A . Fernandez" <ernesto.mnd.fernandez@...il.com>,
        Joe Perches <joe@...ches.com>,
        Viacheslav Dubeyko <slava@...eyko.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Sasha Levin <sashal@...nel.org>, linux-fsdevel@...r.kernel.org
Subject: [PATCH AUTOSEL 4.9 43/45] hfsplus: do not free node before using

From: Pan Bian <bianpan2016@....com>

[ Upstream commit c7d7d620dcbd2a1c595092280ca943f2fced7bbd ]

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.

Link: http://lkml.kernel.org/r/1543053441-66942-1-git-send-email-bianpan2016@163.com
Signed-off-by: Pan Bian <bianpan2016@....com>
Reviewed-by: Andrew Morton <akpm@...ux-foundation.org>
Cc: Ernesto A. Fernandez <ernesto.mnd.fernandez@...il.com>
Cc: Joe Perches <joe@...ches.com>
Cc: Viacheslav Dubeyko <slava@...eyko.com>
Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 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 d9d1a36ba826..8d2256454efe 100644
--- a/fs/hfsplus/btree.c
+++ b/fs/hfsplus/btree.c
@@ -453,14 +453,15 @@ 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;
-- 
2.17.1