[PATCH AUTOSEL 3.18 24/26] hfsplus: do not free node before using

From: Sasha Levin
Date: Wed Dec 05 2018 - 04:56:54 EST


From: Pan Bian <bianpan2016@xxxxxxx>

[ 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@xxxxxxx
Signed-off-by: Pan Bian <bianpan2016@xxxxxxx>
Reviewed-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Ernesto A. Fernandez <ernesto.mnd.fernandez@xxxxxxxxx>
Cc: Joe Perches <joe@xxxxxxxxxxx>
Cc: Viacheslav Dubeyko <slava@xxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
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 3345c7553edc..7adc8a327e03 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