[PATCH 5.5 334/399] bcache: fix use-after-free in register_bcache()

Greg Kroah-Hartman
2020-02-21T07:58:07Z

From: Coly Li <colyli@suse.de>

[ Upstream commit ae3cd299919af6eb670d5af0bc9d7ba14086bd8e ]

The patch "bcache: rework error unwinding in register_bcache" introduces
a use-after-free regression in register_bcache(). Here are current code,
2510 out_free_path:
2511 kfree(path);
2512 out_module_put:
2513 module_put(THIS_MODULE);
2514 out:
2515 pr_info("error %s: %s", path, err);
2516 return ret;
If some error happens and the above code path is executed, at line 2511
path is released, but referenced at line 2515. Then KASAN reports a use-
after-free error message.

This patch changes line 2515 in the following way to fix the problem,
2515 pr_info("error %s: %s", path?path:"", err);

Signed-off-by: Coly Li <colyli@suse.de>
Cc: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/md/bcache/super.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/md/bcache/super.c b/drivers/md/bcache/super.c
index bd2ae1d78fe15..05cb94664efee 100644
--- a/drivers/md/bcache/super.c
+++ b/drivers/md/bcache/super.c
@@ -2475,10 +2475,11 @@ out_free_sb:
kfree(sb);
out_free_path:
kfree(path);
+ path = NULL;
out_module_put:
module_put(THIS_MODULE);
out:
- pr_info("error %s: %s", path, err);
+ pr_info("error %s: %s", path?path:"", err);
return ret;
}

--
2.20.1