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@xxxxxxx Cc: stable@xxxxxxxxxxxxxxx Signed-off-by: Toke Høiland-Jørgensen <toke@xxxxxxxxxx> --- v2: - Return early if the WARN_ON() triggers crypto/algapi.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/crypto/algapi.c b/crypto/algapi.c index d08f864f08be..9de0677b3643 100644 --- a/crypto/algapi.c +++ b/crypto/algapi.c @@ -493,7 +493,9 @@ 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); -- 2.39.2
