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From: David Howells <dhowells@redhat.com>
To: Colin King <colin.king@canonical.com>
Cc: dhowells@redhat.com, linux-afs@lists.infradead.org,
	kernel-janitors@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH][next] afs: fix integer overflow when shifting 1 more than 32 places
Date: Wed, 11 Apr 2018 14:39:26 +0100	[thread overview]
Message-ID: <23535.1523453966@warthog.procyon.org.uk> (raw)
In-Reply-To: <20180411132613.18974-1-colin.king@canonical.com>

Colin King <colin.king@canonical.com> wrote:

> Shifting 1 (a 32 bit signed int) more than 32 places will overflow
> the int, so explicitly use 1ULL to avoid this overflow.
> ...
> -	mask = (1 << nr_slots) - 1;
> +	mask = (1ULL << nr_slots) - 1;

nr_slots cannot be larger than 9, so what I wrote is actually fine and is more
efficient on a 32-bit machine.

David

WARNING: multiple messages have this Message-ID (diff)
From: David Howells <dhowells@redhat.com>
To: Colin King <colin.king@canonical.com>
Cc: dhowells@redhat.com, linux-afs@lists.infradead.org,
	kernel-janitors@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH][next] afs: fix integer overflow when shifting 1 more than 32 places
Date: Wed, 11 Apr 2018 13:39:26 +0000	[thread overview]
Message-ID: <23535.1523453966@warthog.procyon.org.uk> (raw)
In-Reply-To: <20180411132613.18974-1-colin.king@canonical.com>

Colin King <colin.king@canonical.com> wrote:

> Shifting 1 (a 32 bit signed int) more than 32 places will overflow
> the int, so explicitly use 1ULL to avoid this overflow.
> ...
> -	mask = (1 << nr_slots) - 1;
> +	mask = (1ULL << nr_slots) - 1;

nr_slots cannot be larger than 9, so what I wrote is actually fine and is more
efficient on a 32-bit machine.

David

  reply	other threads:[~2018-04-11 13:39 UTC|newest]

Thread overview: 14+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-04-11 13:26 [PATCH][next] afs: fix integer overflow when shifting 1 more than 32 places Colin King
2018-04-11 13:26 ` Colin King
2018-04-11 13:39 ` David Howells [this message]
2018-04-11 13:39   ` David Howells
2018-04-11 13:42   ` Colin Ian King
2018-04-11 13:42     ` Colin Ian King
2018-04-11 14:10   ` David Howells
2018-04-11 14:10     ` David Howells
2018-04-11 14:17     ` Colin Ian King
2018-04-11 14:17       ` Colin Ian King
2018-04-11 15:58     ` Dan Carpenter
2018-04-11 15:58       ` Dan Carpenter
2018-04-11 16:03     ` David Howells
2018-04-11 16:03       ` David Howells

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