linux-kernel - Re: [PATCH net] rds: Fix endian annotations across various assignments

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Message-ID: <20250810183855.GN222315@ZenIV>
Date: Sun, 10 Aug 2025 19:38:55 +0100
From: Al Viro <viro@...iv.linux.org.uk>
To: Ujwal Kundur <ujwal.kundur@...il.com>
Cc: allison.henderson@...cle.com, davem@...emloft.net, edumazet@...gle.com,
	kuba@...nel.org, pabeni@...hat.com, horms@...nel.org,
	netdev@...r.kernel.org, linux-rdma@...r.kernel.org,
	rds-devel@....oracle.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH net] rds: Fix endian annotations across various
 assignments

On Sun, Aug 10, 2025 at 06:47:05PM +0100, Al Viro wrote:

> > diff --git a/net/rds/connection.c b/net/rds/connection.c
> > index d62f486ab29f..0047b76c3c0b 100644
> > --- a/net/rds/connection.c
> > +++ b/net/rds/connection.c
> > @@ -62,13 +62,13 @@ static struct hlist_head *rds_conn_bucket(const struct in6_addr *laddr,
> >  	net_get_random_once(&rds_hash_secret, sizeof(rds_hash_secret));
> >  	net_get_random_once(&rds6_hash_secret, sizeof(rds6_hash_secret));
> >  
> > -	lhash = (__force u32)laddr->s6_addr32[3];
> > +	lhash = (__force __u32)laddr->s6_addr32[3];
> >  #if IS_ENABLED(CONFIG_IPV6)
> >  	fhash = __ipv6_addr_jhash(faddr, rds6_hash_secret);
> >  #else
> > -	fhash = (__force u32)faddr->s6_addr32[3];
> > +	fhash = (__force __u32)(faddr->s6_addr32[3]);
> >  #endif
> > -	hash = __inet_ehashfn(lhash, 0, fhash, 0, rds_hash_secret);
> > +	hash = __inet_ehashfn((__force __be32)lhash, 0, (__force __be32)fhash, 0, rds_hash_secret);
> 
> what the...  You have lhash and fhash set to __be32 values, then
> feed them to function that expects __be32 argument.  Just turn
> these two variables into __be32 and lose the pointless casts.

FWIW, here you do have a missing cast -
	fhash = __ipv6_addr_jhash(faddr, rds6_hash_secret);
should be
	fhash = (__force __be32)__ipv6_addr_jhash(faddr, rds6_hash_secret);
With both fhash and lhash declared as __be32.