[PATCH 05/17] bcache: fix use-after-free in register_bcache()

colyli
2020-01-23T17:02:15Z

From: Coly Li <colyli@suse.de>

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>
---
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 ee7c87f38d0d..fad9c6cbee5e 100644
--- a/drivers/md/bcache/super.c
+++ b/drivers/md/bcache/super.c
@@ -2477,10 +2477,11 @@ static ssize_t register_bcache(struct kobject *k, struct kobj_attribute *attr,
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;
}

--
2.16.4