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From: Arnd Bergmann <arnd@kernel.org>
To: Amitkumar Karwar <amitkarwar@gmail.com>,
	Ganapathi Bhat <ganapathi017@gmail.com>,
	Sharvari Harisangam <sharvari.harisangam@nxp.com>,
	Xinming Hu <huxinming820@gmail.com>,
	Kalle Valo <kvalo@codeaurora.org>
Cc: Arnd Bergmann <arnd@arndb.de>,
	"David S. Miller" <davem@davemloft.net>,
	Jakub Kicinski <kuba@kernel.org>,
	Nathan Chancellor <nathan@kernel.org>,
	Nick Desaulniers <ndesaulniers@google.com>,
	linux-wireless@vger.kernel.org, netdev@vger.kernel.org,
	linux-kernel@vger.kernel.org, llvm@lists.linux.dev
Subject: [PATCH] mwifiex: avoid null-pointer-subtraction warning
Date: Mon, 27 Sep 2021 14:16:35 +0200	[thread overview]
Message-ID: <20210927121656.940304-1-arnd@kernel.org> (raw)

From: Arnd Bergmann <arnd@arndb.de>

clang complains about some NULL pointer arithmetic in this driver:

drivers/net/wireless/marvell/mwifiex/sta_tx.c:65:59: error: performing pointer subtraction with a null pointer has undefined behavior [-Werror,-Wnull-pointer-subtraction]
        pad = ((void *)skb->data - (sizeof(*local_tx_pd) + hroom)-
                                                                 ^
drivers/net/wireless/marvell/mwifiex/uap_txrx.c:478:53: error: performing pointer subtraction with a null pointer has undefined behavior [-Werror,-Wnull-pointer-subtraction]
        pad = ((void *)skb->data - (sizeof(*txpd) + hroom) - NULL) &

Rework that expression to do the same thing using a uintptr_t.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
---
 drivers/net/wireless/marvell/mwifiex/sta_tx.c   | 4 ++--
 drivers/net/wireless/marvell/mwifiex/uap_txrx.c | 4 ++--
 2 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/drivers/net/wireless/marvell/mwifiex/sta_tx.c b/drivers/net/wireless/marvell/mwifiex/sta_tx.c
index 241305377e20..a9b5eb992220 100644
--- a/drivers/net/wireless/marvell/mwifiex/sta_tx.c
+++ b/drivers/net/wireless/marvell/mwifiex/sta_tx.c
@@ -62,8 +62,8 @@ void *mwifiex_process_sta_txpd(struct mwifiex_private *priv,
 
 	pkt_type = mwifiex_is_skb_mgmt_frame(skb) ? PKT_TYPE_MGMT : 0;
 
-	pad = ((void *)skb->data - (sizeof(*local_tx_pd) + hroom)-
-			 NULL) & (MWIFIEX_DMA_ALIGN_SZ - 1);
+	pad = ((uintptr_t)skb->data - (sizeof(*local_tx_pd) + hroom)) &
+	       (MWIFIEX_DMA_ALIGN_SZ - 1);
 	skb_push(skb, sizeof(*local_tx_pd) + pad);
 
 	local_tx_pd = (struct txpd *) skb->data;
diff --git a/drivers/net/wireless/marvell/mwifiex/uap_txrx.c b/drivers/net/wireless/marvell/mwifiex/uap_txrx.c
index 9bbdb8dfce62..245ff644f81e 100644
--- a/drivers/net/wireless/marvell/mwifiex/uap_txrx.c
+++ b/drivers/net/wireless/marvell/mwifiex/uap_txrx.c
@@ -475,8 +475,8 @@ void *mwifiex_process_uap_txpd(struct mwifiex_private *priv,
 
 	pkt_type = mwifiex_is_skb_mgmt_frame(skb) ? PKT_TYPE_MGMT : 0;
 
-	pad = ((void *)skb->data - (sizeof(*txpd) + hroom) - NULL) &
-			(MWIFIEX_DMA_ALIGN_SZ - 1);
+	pad = ((uintptr_t)skb->data - (sizeof(*txpd) + hroom)) &
+	       (MWIFIEX_DMA_ALIGN_SZ - 1);
 
 	skb_push(skb, sizeof(*txpd) + pad);
 
-- 
2.29.2


             reply	other threads:[~2021-09-27 12:17 UTC|newest]

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-09-27 12:16 Arnd Bergmann [this message]
2021-09-28  6:43 ` [PATCH] mwifiex: avoid null-pointer-subtraction warning Kalle Valo
2021-09-28  6:43   ` Kalle Valo
2021-09-28 14:42 ` Kalle Valo
2021-09-28 14:42 ` Kalle Valo

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