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

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Message-ID: <20250810174705.GK222315@ZenIV>
Date: Sun, 10 Aug 2025 18:47:05 +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 10:41:55PM +0530, Ujwal Kundur wrote:

> diff --git a/net/rds/af_rds.c b/net/rds/af_rds.c
> index 086a13170e09..9cd5905d916a 100644
> --- a/net/rds/af_rds.c
> +++ b/net/rds/af_rds.c
> @@ -242,7 +242,7 @@ static __poll_t rds_poll(struct file *file, struct socket *sock,
>  	if (rs->rs_snd_bytes < rds_sk_sndbuf(rs))
>  		mask |= (EPOLLOUT | EPOLLWRNORM);
>  	if (sk->sk_err || !skb_queue_empty(&sk->sk_error_queue))
> -		mask |= POLLERR;
> +		mask |= (__force __poll_t)POLLERR;

EPOLLERR.

>  	read_unlock_irqrestore(&rs->rs_recv_lock, flags);
>  
>  	/* clear state any time we wake a seen-congested socket */
> 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.

> diff --git a/net/rds/rds.h b/net/rds/rds.h
> index dc360252c515..c2fb47e1fe07 100644
> --- a/net/rds/rds.h
> +++ b/net/rds/rds.h
> @@ -93,7 +93,7 @@ enum {
>  
>  /* Max number of multipaths per RDS connection. Must be a power of 2 */
>  #define	RDS_MPATH_WORKERS	8
> -#define	RDS_MPATH_HASH(rs, n) (jhash_1word((rs)->rs_bound_port, \
> +#define	RDS_MPATH_HASH(rs, n) (jhash_1word((__force __u16)(rs)->rs_bound_port, \
>  			       (rs)->rs_hash_initval) & ((n) - 1))

Reasonable.

>  #define IS_CANONICAL(laddr, faddr) (htonl(laddr) < htonl(faddr))
> diff --git a/net/rds/recv.c b/net/rds/recv.c
> index 5627f80013f8..7fc7a3850a7b 100644
> --- a/net/rds/recv.c
> +++ b/net/rds/recv.c
> @@ -216,10 +216,10 @@ static void rds_recv_hs_exthdrs(struct rds_header *hdr,
>  		switch (type) {
>  		case RDS_EXTHDR_NPATHS:
>  			conn->c_npaths = min_t(int, RDS_MPATH_WORKERS,
> -					       be16_to_cpu(buffer.rds_npaths));
> +					      (__force __u16)buffer.rds_npaths);

No.  It will break on little-endian.  That's over-the-wire data you are
dealing with; it's *NOT* going to be host-endian.  Fix the buggered
annotations instead.

>  			break;
>  		case RDS_EXTHDR_GEN_NUM:
> -			new_peer_gen_num = be32_to_cpu(buffer.rds_gen_num);
> +			new_peer_gen_num = (__force __u32)buffer.rds_gen_num;
>  			break;

Ditto.

> diff --git a/net/rds/send.c b/net/rds/send.c
> index 42d991bc8543..0d79455c9721 100644
> --- a/net/rds/send.c
> +++ b/net/rds/send.c
> @@ -1454,8 +1454,8 @@ rds_send_probe(struct rds_conn_path *cp, __be16 sport,
>  
>  	if (RDS_HS_PROBE(be16_to_cpu(sport), be16_to_cpu(dport)) &&
>  	    cp->cp_conn->c_trans->t_mp_capable) {
> -		u16 npaths = cpu_to_be16(RDS_MPATH_WORKERS);
> -		u32 my_gen_num = cpu_to_be32(cp->cp_conn->c_my_gen_num);
> +		u16 npaths = (__force __u16)RDS_MPATH_WORKERS;
> +		u32 my_gen_num = (__force __u32)cp->cp_conn->c_my_gen_num;

Again, over-the-wire data; you are breaking it on l-e.

>  		rds_message_add_extension(&rm->m_inc.i_hdr,
>  					  RDS_EXTHDR_NPATHS, &npaths,