linux-kernel - [v2 PATCH] crypto: caam - Avoid GCC memset bug warning

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Date:   Wed, 28 Dec 2022 19:03:32 +0800
From:   Herbert Xu <herbert@...dor.apana.org.au>
To:     Uwe Kleine-König 
        <u.kleine-koenig@...gutronix.de>
Cc:     Anders Roxell <anders.roxell@...aro.org>,
        Kees Cook <keescook@...omium.org>,
        Horia Geantă <horia.geanta@....com>,
        Gaurav Jain <gaurav.jain@....com>,
        Pankaj Gupta <pankaj.gupta@....com>,
        linux-kernel@...r.kernel.org, linux-hardening@...r.kernel.org,
        linux-crypto@...r.kernel.org, kernel@...gutronix.de,
        "David S. Miller" <davem@...emloft.net>,
        kernel test robot <lkp@...el.com>
Subject: [v2 PATCH] crypto: caam - Avoid GCC memset bug warning

On Wed, Dec 28, 2022 at 10:39:17AM +0100, Uwe Kleine-König wrote:
>
> Huh, broken encoding in the mail. I'd appreciate someone to doublecheck
> it's fine in the final commit.
> 
> Tested-by: Uwe Kleine-König <u.kleine-koenig@...gutronix.de>

Sorry.  Let me try again:

---8<---
Certain versions of gcc don't like the memcpy with a NULL dst
(which only happens with a zero length).  This only happens
when debugging is enabled so add an if clause to work around
these warnings.

A similar warning used to be generated by sparse but that was
fixed years ago.

Link: https://lore.kernel.org/lkml/202210290446.qBayTfzl-lkp@intel.com
Reported-by: kernel test robot <lkp@...el.com>
Reported-by: Kees Cook <keescook@...omium.org>
Reported-by: Uwe Kleine-König <u.kleine-koenig@...gutronix.de>
Tested-by: Uwe Kleine-König <u.kleine-koenig@...gutronix.de>
Signed-off-by: Herbert Xu <herbert@...dor.apana.org.au>

diff --git a/drivers/crypto/caam/desc_constr.h b/drivers/crypto/caam/desc_constr.h
index 62ce6421bb3f..824c94d44f94 100644
--- a/drivers/crypto/caam/desc_constr.h
+++ b/drivers/crypto/caam/desc_constr.h
@@ -163,7 +163,8 @@ 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 */
+	/* Avoid gcc warning: memcpy with data == NULL */
+	if (!IS_ENABLED(CONFIG_CRYPTO_DEV_FSL_CAAM_DEBUG) || data)
 		memcpy(offset, data, len);
 
 	(*desc) = cpu_to_caam32(caam32_to_cpu(*desc) +
-- 
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