libceph: don't call crypto_free_sync_skcipher() on a NULL tfm

In set_secret(), key->tfm is assigned to NULL on line 55, and then
ceph_crypto_key_destroy(key) is executed.

ceph_crypto_key_destroy(key)
  crypto_free_sync_skcipher(key->tfm)
    crypto_free_skcipher(&tfm->base);

This happens to work because crypto_sync_skcipher is a trivial wrapper
around crypto_skcipher: &tfm->base is still 0 and crypto_free_skcipher()
handles that.  Let's not rely on the layout of crypto_sync_skcipher.

This bug is found by a static analysis tool STCheck written by us.

Fixes: 69d6302b65a8 ("libceph: Remove VLA usage of skcipher").
Signed-off-by: Jia-Ju Bai <baijiaju1990@gmail.com>
Reviewed-by: Ilya Dryomov <idryomov@gmail.com>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>

diff --git a/net/ceph/crypto.c b/net/ceph/crypto.c
index 5d6724cee38f90d1cbafcd6e66eb731394dad43c..4f75df40fb121f3c955f916fac5a3bb7f64d7f40 100644 (file)
--- a/net/ceph/crypto.c
+++ b/net/ceph/crypto.c
@@ -136,8 +136,10 @@ void ceph_crypto_key_destroy(struct ceph_crypto_key *key)
        if (key) {
                kfree(key->key);
                key->key = NULL;
-               crypto_free_sync_skcipher(key->tfm);
-               key->tfm = NULL;
+               if (key->tfm) {
+                       crypto_free_sync_skcipher(key->tfm);
+                       key->tfm = NULL;
+               }
        }
 }