Re: [PATCH linux-next] crypto: api - Avoid NULL pointer dereference in crypto_larval_destroy()

[Eric Biggers <ebiggers@kernel.org>]

On Tue, Aug 16, 2022 at 11:37:22AM +0000, cgel.zte@gmail.com wrote:
> From: ye xingchen <ye.xingchen@zte.com.cn>
> 
> When we have no primary larval or when it's a software node, we may end up
>  in the situation when larval is a NULL pointer. There is no point to look
> for secondary larval in such case. Add a necessary check to a condition.
> 
> Reported-by: Zeal Robot <zealci@zte.com.cn>
> Signed-off-by: ye xingchen <ye.xingchen@zte.com.cn>
> ---
>  crypto/api.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/crypto/api.c b/crypto/api.c
> index 69508ae9345e..f2399aac831d 100644
> --- a/crypto/api.c
> +++ b/crypto/api.c
> @@ -96,7 +96,7 @@ static void crypto_larval_destroy(struct crypto_alg *alg)
>  	struct crypto_larval *larval = (void *)alg;
>  
>  	BUG_ON(!crypto_is_larval(alg));
> -	if (!IS_ERR_OR_NULL(larval->adult))
> +	if (larval && !IS_ERR_OR_NULL(larval->adult))
>  		crypto_mod_put(larval->adult);
>  	kfree(larval);
>  }
> -- 

How does this new NULL check do anything when the pointer is unconditionally
dereferenced in the previous line?

- Eric