hfsplus: do not free node before using

BugLink: https://bugs.launchpad.net/bugs/1837161
[ 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@163.com>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Ernesto A. Fernandez <ernesto.mnd.fernandez@gmail.com>
Cc: Joe Perches <joe@perches.com>
Cc: Viacheslav Dubeyko <slava@dubeyko.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
Signed-off-by: Khalid Elmously <khalid.elmously@canonical.com>

diff --git a/fs/hfsplus/btree.c b/fs/hfsplus/btree.c
index de14b2b6881bb73c421bea985873848641c8e9a9..3de3bc4918b551314004bd4b76c92d2c1e9aa0a9 100644 (file)
--- a/fs/hfsplus/btree.c
+++ b/fs/hfsplus/btree.c
@@ -454,14 +454,15 @@ 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;