linux-ext4 - Re: [PATCH v1 3/5] treewide: use get_random

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Date:   Wed, 12 Oct 2022 12:16:53 -0700
From:   Joe Perches <joe@...ches.com>
To:     "Jason A. Donenfeld" <Jason@...c4.com>,
        linux-kernel@...r.kernel.org
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Subject: Re: [PATCH v1 3/5] treewide: use get_random_u32() when possible

On Wed, 2022-10-05 at 23:48 +0200, Jason A. Donenfeld wrote:
> The prandom_u32() function has been a deprecated inline wrapper around
> get_random_u32() for several releases now, and compiles down to the
> exact same code. Replace the deprecated wrapper with a direct call to
> the real function.
[]
> diff --git a/drivers/infiniband/hw/cxgb4/cm.c b/drivers/infiniband/hw/cxgb4/cm.c
[]
> @@ -734,7 +734,7 @@ static int send_connect(struct c4iw_ep *ep)
>  				   &ep->com.remote_addr;
>  	int ret;
>  	enum chip_type adapter_type = ep->com.dev->rdev.lldi.adapter_type;
> -	u32 isn = (prandom_u32() & ~7UL) - 1;
> +	u32 isn = (get_random_u32() & ~7UL) - 1;

trivia:

There are somewhat odd size mismatches here.

I had to think a tiny bit if random() returned a value from 0 to 7
and was promoted to a 64 bit value then truncated to 32 bit.

Perhaps these would be clearer as ~7U and not ~7UL

>  	struct net_device *netdev;
>  	u64 params;
>  
> @@ -2469,7 +2469,7 @@ static int accept_cr(struct c4iw_ep *ep, struct sk_buff *skb,
>  	}
>  
>  	if (!is_t4(adapter_type)) {
> -		u32 isn = (prandom_u32() & ~7UL) - 1;
> +		u32 isn = (get_random_u32() & ~7UL) - 1;

etc...

drivers/infiniband/hw/cxgb4/cm.c:	u32 isn = (prandom_u32() & ~7UL) - 1;
drivers/infiniband/hw/cxgb4/cm.c:		u32 isn = (prandom_u32() & ~7UL) - 1;
drivers/net/ethernet/chelsio/inline_crypto/chtls/chtls_cm.c:	rpl5->iss = cpu_to_be32((prandom_u32() & ~7UL) - 1);
drivers/scsi/cxgbi/cxgb4i/cxgb4i.c:		u32 isn = (prandom_u32() & ~7UL) - 1;
drivers/scsi/cxgbi/cxgb4i/cxgb4i.c:		u32 isn = (prandom_u32() & ~7UL) - 1;
drivers/target/iscsi/cxgbit/cxgbit_cm.c:	rpl5->iss = cpu_to_be32((prandom_u32() & ~7UL) - 1);