netdev - Re: [PATCH] netlink: Don't shift on 64 for ngroups

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Message-Id: <20180804.170856.2031275734761112973.davem@davemloft.net>
Date:   Sat, 04 Aug 2018 17:08:56 -0700 (PDT)
From:   David Miller <davem@...emloft.net>
To:     dima@...sta.com
Cc:     linux-kernel@...r.kernel.org, natechancellor@...il.com,
        herbert@...dor.apana.org.au, steffen.klassert@...unet.com,
        netdev@...r.kernel.org, stable@...r.kernel.org
Subject: Re: [PATCH] netlink: Don't shift on 64 for ngroups

From: Dmitry Safonov <dima@...sta.com>
Date: Sun,  5 Aug 2018 00:55:44 +0100

> @@ -1011,8 +1011,8 @@ static int netlink_bind(struct socket *sock, struct sockaddr *addr,
>  
>  	if (nlk->ngroups == 0)
>  		groups = 0;
> -	else
> -		groups &= (1ULL << nlk->ngroups) - 1;
> +	else if (nlk->ngroups < sizeof(long unsigned int))
> +		groups &= (1UL << nlk->ngroups) - 1;

Sizeof is in bytes, you want to compare against bits.