[PATCH v3] crypto/algapi: fix refcount leak in crypto_register_alg()

[Wentao Liang]

When crypto_register_alg() calls crypto_check_alg() successfully,
the algorithm's refcount is set to one.  If the subsequent handling
for CRYPTO_ALG_DUP_FIRST fails with ENOMEM due to a kmemdup()
error, the function returns without decrementing the refcount.
This leaves the algorithm forever pinned with a leaked reference.

Fix it by calling crypto_alg_put() on the kmemdup() failure path,
matching the error handling used elsewhere in the function.

Cc: stable@xxxxxxxxxxxxxxx
Fixes: f1440a90465b ("crypto: api - Add support for duplicating algorithms before registration")
Signed-off-by: Wentao Liang <vulab@xxxxxxxxxxx>

---
Changes in v2:
- Clarify the refcount lifecycle.
- Fix code error.
---
 crypto/algapi.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/crypto/algapi.c b/crypto/algapi.c
index 37de377719ae..260d03b328ec 100644
--- a/crypto/algapi.c
+++ b/crypto/algapi.c
@@ -446,8 +446,10 @@ int crypto_register_alg(struct crypto_alg *alg)
 		u8 *p = (u8 *)alg - algsize;
 
 		p = kmemdup(p, algsize + sizeof(*alg), GFP_KERNEL);
-		if (!p)
+		if (!p) {
+			crypto_alg_put(alg);
 			return -ENOMEM;
+		}
 
 		alg = (void *)(p + algsize);
 		alg->cra_destroy = crypto_free_alg;
-- 
2.34.1