linux-kernel - [PATCH AUTOSEL 4.19 117/123] hfs: do not free node before using

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Date:   Wed,  5 Dec 2018 04:35:49 -0500
From:   Sasha Levin <sashal@...nel.org>
To:     stable@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:     Pan Bian <bianpan2016@....com>, Joe Perches <joe@...ches.com>,
        "Ernesto A . Fernandez" <ernesto.mnd.fernandez@...il.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 4.19 117/123] hfs: do not free node before using

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

[ Upstream commit ce96a407adef126870b3f4a1b73529dd8aa80f49 ]

hfs_bmap_free() frees the 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 the node only when
it is never again used.

Link: http://lkml.kernel.org/r/1542963889-128825-1-git-send-email-bianpan2016@163.com
Fixes: a1185ffa2fc ("HFS rewrite")
Signed-off-by: Pan Bian <bianpan2016@....com>
Reviewed-by: Andrew Morton <akpm@...ux-foundation.org>
Cc: Joe Perches <joe@...ches.com>
Cc: Ernesto A. Fernandez <ernesto.mnd.fernandez@...il.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/hfs/btree.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/fs/hfs/btree.c b/fs/hfs/btree.c
index 374b5688e29e..9bdff5e40626 100644
--- a/fs/hfs/btree.c
+++ b/fs/hfs/btree.c
@@ -329,13 +329,14 @@ 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;
-- 
2.17.1