Passing num_mb=0 to the multibuffer speed tests leaves test_mb_aead_cycles()
and test_mb_acipher_cycles() dividing by (8 * num_mb). With sec=0 (the
default), the module prints "1 operation in ..." and hits a divide-by-zero
fault.

Force num_mb to at least 1 during module init and warn the caller so the
warm-up loop and the final report stay well-defined.

To reproduce:
sudo modprobe tcrypt mode=600 num_mb=0

Signed-off-by: Saeed Mirzamohammadi <saeed.mirzamohammadi@oracle.com>
---
 crypto/tcrypt.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/crypto/tcrypt.c b/crypto/tcrypt.c
index aded375461374..61c8cf55c4f1e 100644
--- a/crypto/tcrypt.c
+++ b/crypto/tcrypt.c
@@ -2808,6 +2808,11 @@ static int __init tcrypt_mod_init(void)
 			goto err_free_tv;
 	}
 
+	if (!num_mb) {
+		pr_warn("num_mb must be at least 1; forcing to 1\n");
+		num_mb = 1;
+	}
+
 	err = do_test(alg, type, mask, mode, num_mb);
 
 	if (err) {
-- 
2.50.1

On Mon, Mar 02, 2026 at 03:59:14PM -0800, Saeed Mirzamohammadi wrote:
> Passing num_mb=0 to the multibuffer speed tests leaves test_mb_aead_cycles()
> and test_mb_acipher_cycles() dividing by (8 * num_mb). With sec=0 (the
> default), the module prints "1 operation in ..." and hits a divide-by-zero
> fault.
> 
> Force num_mb to at least 1 during module init and warn the caller so the
> warm-up loop and the final report stay well-defined.
> 
> To reproduce:
> sudo modprobe tcrypt mode=600 num_mb=0
> 
> Signed-off-by: Saeed Mirzamohammadi <saeed.mirzamohammadi@oracle.com>
> ---
>  crypto/tcrypt.c | 5 +++++
>  1 file changed, 5 insertions(+)

Patch applied.  Thanks.
-- 
Email: Herbert Xu <herbert@gondor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt