linux-kernel - [PATCH 08/11] atmel: avoid gcc -Wstringop-overflow warning

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Date:   Mon, 22 Mar 2021 17:02:46 +0100
From:   Arnd Bergmann <arnd@...nel.org>
To:     linux-kernel@...r.kernel.org, Martin Sebor <msebor@....gnu.org>,
        Simon Kelley <simon@...kelleys.org.uk>,
        Kalle Valo <kvalo@...eaurora.org>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>
Cc:     Arnd Bergmann <arnd@...db.de>, x86@...nel.org,
        Ning Sun <ning.sun@...el.com>,
        Jani Nikula <jani.nikula@...ux.intel.com>,
        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,
        Lee Jones <lee.jones@...aro.org>,
        Pascal Terjan <pterjan@...gle.com>,
        "Gustavo A. R. Silva" <gustavoars@...nel.org>
Subject: [PATCH 08/11] atmel: avoid gcc -Wstringop-overflow warning

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

gcc-11 notices that the fields as defined in the ass_req_format
structure do not match the actual use of that structure:

cc1: error: writing 4 bytes into a region of size between 18446744073709551613 and 2 [-Werror=stringop-overflow=]
drivers/net/wireless/atmel/atmel.c:2884:20: note: at offset [4, 6] into destination object ‘ap’ of size 6
 2884 |                 u8 ap[ETH_ALEN]; /* nothing after here directly accessible */
      |                    ^~
drivers/net/wireless/atmel/atmel.c:2885:20: note: at offset [4, 6] into destination object ‘ssid_el_id’ of size 1
 2885 |                 u8 ssid_el_id;
      |                    ^~~~~~~~~~

This is expected here because the actual structure layout is variable.
As the code does not actually access the individual fields, replace
them with a comment and fixed-length array so prevent gcc from
complaining about it.

Signed-off-by: Arnd Bergmann <arnd@...db.de>
---
 drivers/net/wireless/atmel/atmel.c | 25 +++++++++++++++----------
 1 file changed, 15 insertions(+), 10 deletions(-)

diff --git a/drivers/net/wireless/atmel/atmel.c b/drivers/net/wireless/atmel/atmel.c
index 707fe66727f8..ff9152d600e1 100644
--- a/drivers/net/wireless/atmel/atmel.c
+++ b/drivers/net/wireless/atmel/atmel.c
@@ -2881,13 +2881,18 @@ static void send_association_request(struct atmel_private *priv, int is_reassoc)
 	struct ass_req_format {
 		__le16 capability;
 		__le16 listen_interval;
-		u8 ap[ETH_ALEN]; /* nothing after here directly accessible */
-		u8 ssid_el_id;
-		u8 ssid_len;
-		u8 ssid[MAX_SSID_LENGTH];
-		u8 sup_rates_el_id;
-		u8 sup_rates_len;
-		u8 rates[4];
+		u8 ssid_el[ETH_ALEN + 2 + MAX_SSID_LENGTH + 2 + 4];
+		/*
+		 * nothing after here directly accessible:
+		 *
+		 * u8 ap[ETH_ALEN];
+		 * u8 ssid_el_id;
+		 * u8 ssid_len;
+		 * u8 ssid[MAX_SSID_LENGTH];
+		 * u8 sup_rates_el_id;
+		 * u8 sup_rates_len;
+		 * u8 rates[4];
+		 */
 	} body;
 
 	header.frame_control = cpu_to_le16(IEEE80211_FTYPE_MGMT |
@@ -2907,13 +2912,13 @@ static void send_association_request(struct atmel_private *priv, int is_reassoc)
 
 	body.listen_interval = cpu_to_le16(priv->listen_interval * priv->beacon_period);
 
+	ssid_el_p = body.ssid_el;
 	/* current AP address - only in reassoc frame */
 	if (is_reassoc) {
-		memcpy(body.ap, priv->CurrentBSSID, ETH_ALEN);
-		ssid_el_p = &body.ssid_el_id;
+		memcpy(ssid_el_p, priv->CurrentBSSID, ETH_ALEN);
+		ssid_el_p += ETH_ALEN;
 		bodysize = 18 + priv->SSID_size;
 	} else {
-		ssid_el_p = &body.ap[0];
 		bodysize = 12 + priv->SSID_size;
 	}
 
-- 
2.29.2