linux-hardening - [PATCH v2] p54: Replace zero-length array of trailing structs with flex-array

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Message-Id: <20221118234240.gonna.369-kees@kernel.org>
Date:   Fri, 18 Nov 2022 15:42:44 -0800
From:   Kees Cook <keescook@...omium.org>
To:     Christian Lamparter <chunkeey@...glemail.com>
Cc:     Kees Cook <keescook@...omium.org>, Kalle Valo <kvalo@...nel.org>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        "Gustavo A. R. Silva" <gustavoars@...nel.org>,
        linux-wireless@...r.kernel.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-hardening@...r.kernel.org
Subject: [PATCH v2] p54: Replace zero-length array of trailing structs with flex-array

Zero-length arrays are deprecated[1] and are being replaced with
flexible array members in support of the ongoing efforts to tighten the
FORTIFY_SOURCE routines on memcpy(), correctly instrument array indexing
with UBSAN_BOUNDS, and to globally enable -fstrict-flex-arrays=3.

Replace zero-length array with flexible-array member.

This results in no differences in binary output (most especially because
struct pda_antenna_gain is unused). The struct is kept for future
reference.

[1] https://github.com/KSPP/linux/issues/78

Cc: Christian Lamparter <chunkeey@...glemail.com>
Cc: Kalle Valo <kvalo@...nel.org>
Cc: "David S. Miller" <davem@...emloft.net>
Cc: Eric Dumazet <edumazet@...gle.com>
Cc: Jakub Kicinski <kuba@...nel.org>
Cc: Paolo Abeni <pabeni@...hat.com>
Cc: "Gustavo A. R. Silva" <gustavoars@...nel.org>
Cc: linux-wireless@...r.kernel.org
Cc: netdev@...r.kernel.org
Signed-off-by: Kees Cook <keescook@...omium.org>
---
v2:
- convert normally (chunkeey)
v1: https://lore.kernel.org/lkml/20221118210639.never.072-kees@kernel.org/
---
 drivers/net/wireless/intersil/p54/eeprom.h | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/net/wireless/intersil/p54/eeprom.h b/drivers/net/wireless/intersil/p54/eeprom.h
index 1d0aaf54389a..641c4e79879e 100644
--- a/drivers/net/wireless/intersil/p54/eeprom.h
+++ b/drivers/net/wireless/intersil/p54/eeprom.h
@@ -108,10 +108,10 @@ struct pda_country {
 } __packed;
 
 struct pda_antenna_gain {
-	struct {
+	DECLARE_FLEX_ARRAY(struct {
 		u8 gain_5GHz;	/* 0.25 dBi units */
 		u8 gain_2GHz;	/* 0.25 dBi units */
-	} __packed antenna[0];
+	} __packed, antenna);
 } __packed;
 
 struct pda_custom_wrapper {
-- 
2.34.1