linux-kernel - [PATCH 07/11] ARM: sharpsl_param: work around -Wstringop-overread warning

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Date:   Mon, 22 Mar 2021 17:02:45 +0100
From:   Arnd Bergmann <arnd@...nel.org>
To:     linux-kernel@...r.kernel.org, Martin Sebor <msebor@....gnu.org>
Cc:     Arnd Bergmann <arnd@...db.de>, x86@...nel.org,
        Ning Sun <ning.sun@...el.com>,
        Jani Nikula <jani.nikula@...ux.intel.com>,
        Kalle Valo <kvalo@...eaurora.org>,
        Simon Kelley <simon@...kelleys.org.uk>,
        James Smart <james.smart@...adcom.com>,
        "James E.J. Bottomley" <jejb@...ux.ibm.com>,
        Anders Larsen <al@...rsen.net>, Tejun Heo <tj@...nel.org>,
        Serge Hallyn <serge@...lyn.com>,
        Imre Deak <imre.deak@...el.com>,
        linux-arm-kernel@...ts.infradead.org,
        tboot-devel@...ts.sourceforge.net, intel-gfx@...ts.freedesktop.org,
        dri-devel@...ts.freedesktop.org, ath11k@...ts.infradead.org,
        linux-wireless@...r.kernel.org, netdev@...r.kernel.org,
        linux-scsi@...r.kernel.org, cgroups@...r.kernel.org,
        linux-security-module@...r.kernel.org,
        Russell King <linux@...linux.org.uk>
Subject: [PATCH 07/11] ARM: sharpsl_param: work around -Wstringop-overread warning

From: Arnd Bergmann <arnd@...db.de>

gcc warns that accessing a pointer based on a numeric constant may
be an offset into a NULL pointer, and would therefore has zero
accessible bytes:

arch/arm/common/sharpsl_param.c: In function ‘sharpsl_save_param’:
arch/arm/common/sharpsl_param.c:43:9: error: ‘memcpy’ reading 64 bytes from a region of size 0 [-Werror=stringop-overread]
   43 |         memcpy(&sharpsl_param, param_start(PARAM_BASE), sizeof(struct sharpsl_param_info));
      |         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

In this particular case, the warning is bogus since this is the actual
pointer, not an offset on a NULL pointer. Add a local variable to shut
up the warning and hope it doesn't come back.

Link: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99578
Signed-off-by: Arnd Bergmann <arnd@...db.de>
---
 arch/arm/common/sharpsl_param.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/arch/arm/common/sharpsl_param.c b/arch/arm/common/sharpsl_param.c
index efeb5724d9e9..6237ede2f0c7 100644
--- a/arch/arm/common/sharpsl_param.c
+++ b/arch/arm/common/sharpsl_param.c
@@ -40,7 +40,9 @@ EXPORT_SYMBOL(sharpsl_param);
 
 void sharpsl_save_param(void)
 {
-	memcpy(&sharpsl_param, param_start(PARAM_BASE), sizeof(struct sharpsl_param_info));
+	struct sharpsl_param_info *params = param_start(PARAM_BASE);
+
+	memcpy(&sharpsl_param, params, sizeof(*params));
 
 	if (sharpsl_param.comadj_keyword != COMADJ_MAGIC)
 		sharpsl_param.comadj=-1;
-- 
2.29.2