hfsplus: do not free node before using

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>

diff --git a/fs/hfsplus/btree.c b/fs/hfsplus/btree.c
index 236efe51eca6790e8bf05b679f92683f4c1aa35a..66774f4cb4fd5e34ae98de0d9a8ef9528bcfb47c 100644 (file)
--- 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;