linux-kernel - RE: [PATCH v2 2/5] staging: r8188eu: cast to restricted _

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Message-ID: <05aafb94be1b4e609250313709cd668d@AcuMS.aculab.com>
Date:   Sun, 22 Aug 2021 21:30:45 +0000
From:   David Laight <David.Laight@...LAB.COM>
To:     'Larry Finger' <Larry.Finger@...inger.net>,
        Aakash Hemadri <aakashhemadri123@...il.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Phillip Potter <phil@...lpotter.co.uk>
CC:     "linux-staging@...ts.linux.dev" <linux-staging@...ts.linux.dev>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH v2 2/5] staging: r8188eu: cast to restricted __be32

From: Larry Finger
> Sent: 20 August 2021 22:45
> 
> On 8/19/21 3:17 AM, Aakash Hemadri wrote:
> > Fix sparse warning:
> >> rtw_br_ext.c:836:54: warning: cast to restricted __be32
> >
> > Unnecessary double cast, remove them.
> >
> > Signed-off-by: Aakash Hemadri <aakashhemadri123@...il.com>
> > ---
> >   drivers/staging/r8188eu/core/rtw_br_ext.c | 2 +-
> >   1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/drivers/staging/r8188eu/core/rtw_br_ext.c b/drivers/staging/r8188eu/core/rtw_br_ext.c
> > index 404fa8904e47..6a0462ce6230 100644
> > --- a/drivers/staging/r8188eu/core/rtw_br_ext.c
> > +++ b/drivers/staging/r8188eu/core/rtw_br_ext.c
> > @@ -671,7 +671,7 @@ void dhcp_flag_bcast(struct adapter *priv, struct sk_buff *skb)
> >   				    (udph->dest == __constant_htons(SERVER_PORT))) { /*  DHCP request */
> >   					struct dhcpMessage *dhcph =
> >   						(struct dhcpMessage *)((size_t)udph + sizeof(struct udphdr));
> > -					u32 cookie = be32_to_cpu((__be32)dhcph->cookie);
> > +					u32 cookie = dhcph->cookie;
> >
> >   					if (cookie == DHCP_MAGIC) { /*  match magic word */
> >   						if (!(dhcph->flags & htons(BROADCAST_FLAG))) {
> >
> 
> This patch is wrong. All the documentation I could find tells me that the
> multi-byte entries in dhcph are big-endian, thus the new line should read:
> 
> 					u32 cookie = be32_to_cpu(dhcph->cookie);

Modulo anything that really means it should get_unaligned_be32().

	David

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