linux-kernel - Re: [PATCH v6 1/4] sgl_alloc_order: remove 4 GiB limit, sgl

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Message-ID: <20210119125904.GR4605@ziepe.ca>
Date:   Tue, 19 Jan 2021 08:59:04 -0400
From:   Jason Gunthorpe <jgg@...pe.ca>
To:     Douglas Gilbert <dgilbert@...erlog.com>
Cc:     Bodo Stroesser <bostroesser@...il.com>, linux-scsi@...r.kernel.org,
        linux-block@...r.kernel.org, target-devel@...r.kernel.org,
        linux-rdma@...r.kernel.org, linux-kernel@...r.kernel.org,
        martin.petersen@...cle.com, jejb@...ux.vnet.ibm.com, ddiss@...e.de,
        bvanassche@....org
Subject: Re: [PATCH v6 1/4] sgl_alloc_order: remove 4 GiB limit, sgl_free()
 warning

On Mon, Jan 18, 2021 at 08:27:09PM -0500, Douglas Gilbert wrote:

> To protect against the "unsigned long long" length being too big why
> not pick a large power of two and if someone can justify a larger
> value, they can send a patch.
> 
>         if (length > 64ULL * 1024 * 1024 * 1024)
> 		return NULL;

That is not how we protect against arithemetic overflows in the kernel

Jason