crypto: api - Demote BUG_ON() in crypto_unregister_alg() to a WARN_ON()

The crypto_unregister_alg() function expects callers to ensure that any
algorithm that is unregistered has a refcnt of exactly 1, and issues a
BUG_ON() if this is not the case. However, there are in fact drivers that
will call crypto_unregister_alg() without ensuring that the refcnt has been
lowered first, most notably on system shutdown. This causes the BUG_ON() to
trigger, which prevents a clean shutdown and hangs the system.

To avoid such hangs on shutdown, demote the BUG_ON() in
crypto_unregister_alg() to a WARN_ON() with early return. Cc stable because
this problem was observed on a 6.2 kernel, cf the link below.

Link: https://lore.kernel.org/r/87r0tyq8ph.fsf@toke.dk
Cc: stable@vger.kernel.org
Signed-off-by: Toke Høiland-Jørgensen <toke@redhat.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

diff --git a/crypto/algapi.c b/crypto/algapi.c
index 9b7e263..d7eb8f9 100644 (file)
--- a/crypto/algapi.c
+++ b/crypto/algapi.c
@@ -491,7 +491,9 @@ void crypto_unregister_alg(struct crypto_alg *alg)
        if (WARN(ret, "Algorithm %s is not registered", alg->cra_driver_name))
                return;
 
-       BUG_ON(refcount_read(&alg->cra_refcnt) != 1);
+       if (WARN_ON(refcount_read(&alg->cra_refcnt) != 1))
+               return;
+
        if (alg->cra_destroy)
                alg->cra_destroy(alg);