dm crypt: fix free of bad values after tfm allocation failure

If crypt_alloc_tfms() had to allocate multiple tfms and it failed before
the last allocation, then it would call crypt_free_tfms() and could free
pointers from uninitialized memory -- due to the crypt_free_tfms() check
for non-zero cc->tfms[i].  Fix by allocating zeroed memory.

Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Cc: stable@vger.kernel.org
diff --git a/drivers/md/dm-crypt.c b/drivers/md/dm-crypt.c
index d609566..8742957 100644
--- a/drivers/md/dm-crypt.c
+++ b/drivers/md/dm-crypt.c
@@ -1453,7 +1453,7 @@
 	unsigned i;
 	int err;
 
-	cc->tfms = kmalloc(cc->tfms_count * sizeof(struct crypto_skcipher *),
+	cc->tfms = kzalloc(cc->tfms_count * sizeof(struct crypto_skcipher *),
 			   GFP_KERNEL);
 	if (!cc->tfms)
 		return -ENOMEM;