linux-hardening - Re: [PATCH v2] crypto/caam: Avoid GCC constprop bug warning

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Message-ID: <Y4mHjKXnF/4Pfw5I@gondor.apana.org.au>
Date:   Fri, 2 Dec 2022 13:05:16 +0800
From:   Herbert Xu <herbert@...dor.apana.org.au>
To:     Kees Cook <keescook@...omium.org>
Cc:     Horia Geantă <horia.geanta@....com>,
        Pankaj Gupta <pankaj.gupta@....com>,
        Gaurav Jain <gaurav.jain@....com>,
        "David S. Miller" <davem@...emloft.net>,
        linux-crypto@...r.kernel.org, kernel test robot <lkp@...el.com>,
        Anders Roxell <anders.roxell@...aro.org>,
        linux-kernel@...r.kernel.org, linux-hardening@...r.kernel.org
Subject: Re: [PATCH v2] crypto/caam: Avoid GCC constprop bug warning

On Thu, Dec 01, 2022 at 07:30:22PM -0800, Kees Cook wrote:
>
> Getting rid of the if doesn't solve the warning. I can switch it to just
> "if (data)", though. That keeps GCC happy.

OK I misread the thread.

Anyhow, it appears that this warning only occurs due to a debug
printk in caam.  So how about something like this?

diff --git a/drivers/crypto/caam/desc_constr.h b/drivers/crypto/caam/desc_constr.h
index 62ce6421bb3f..b49c995e1cc6 100644
--- a/drivers/crypto/caam/desc_constr.h
+++ b/drivers/crypto/caam/desc_constr.h
@@ -163,7 +163,7 @@ static inline void append_data(u32 * const desc, const void *data, int len)
 {
 	u32 *offset = desc_end(desc);
 
-	if (len) /* avoid sparse warning: memcpy with byte count of 0 */
+	if (!IS_ENABLED(CONFIG_CRYPTO_DEV_FSL_CAAM_DEBUG) || data)
 		memcpy(offset, data, len);
 
 	(*desc) = cpu_to_caam32(caam32_to_cpu(*desc) +

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