Re: [PATCH] crypto: public_key: check that pkey_algo is non-NULL before passing it to strcmp()

[Jarkko Sakkinen <jarkko@kernel.org>]

On Wed, Jan 13, 2021 at 11:11:13AM +0000, David Howells wrote:
> I'm intending to use Tianjia's patch.  Would you like to add a Reviewed-by?
> 
> David

I can give.

Reviewed-by: Jarkko Sakkinen <jarkko@kernel.org>

/Jarkko

> ---
> commit 11078a592e6dcea6b9f30e822d3d30e3defc99ca
> Author: Tianjia Zhang <tianjia.zhang@linux.alibaba.com>
> Date:   Thu Jan 7 17:28:55 2021 +0800
> 
>     X.509: Fix crash caused by NULL pointer
>     
>     On the following call path, `sig->pkey_algo` is not assigned
>     in asymmetric_key_verify_signature(), which causes runtime
>     crash in public_key_verify_signature().
>     
>       keyctl_pkey_verify
>         asymmetric_key_verify_signature
>           verify_signature
>             public_key_verify_signature
>     
>     This patch simply check this situation and fixes the crash
>     caused by NULL pointer.
>     
>     Fixes: 215525639631 ("X.509: support OSCCA SM2-with-SM3 certificate verification")
>     Cc: stable@vger.kernel.org # v5.10+
>     Reported-by: Tobias Markus <tobias@markus-regensburg.de>
>     Signed-off-by: Tianjia Zhang <tianjia.zhang@linux.alibaba.com>
>     Signed-off-by: David Howells <dhowells@redhat.com>
> 
> diff --git a/crypto/asymmetric_keys/public_key.c b/crypto/asymmetric_keys/public_key.c
> index 8892908ad58c..788a4ba1e2e7 100644
> --- a/crypto/asymmetric_keys/public_key.c
> +++ b/crypto/asymmetric_keys/public_key.c
> @@ -356,7 +356,8 @@ int public_key_verify_signature(const struct public_key *pkey,
>  	if (ret)
>  		goto error_free_key;
>  
> -	if (strcmp(sig->pkey_algo, "sm2") == 0 && sig->data_size) {
> +	if (sig->pkey_algo && strcmp(sig->pkey_algo, "sm2") == 0 &&
> +	    sig->data_size) {
>  		ret = cert_sig_digest_update(sig, tfm);
>  		if (ret)
>  			goto error_free_key;
> 
>