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

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Date:   Tue, 19 Jan 2021 19:08:32 +0100
From:   Bodo Stroesser <bostroesser@...il.com>
To:     Jason Gunthorpe <jgg@...pe.ca>
Cc:     Douglas Gilbert <dgilbert@...erlog.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 19.01.21 19:03, Jason Gunthorpe wrote:
> On Tue, Jan 19, 2021 at 06:24:49PM +0100, Bodo Stroesser wrote:
>>
>> I had a second look into math.h, but I don't find any reason why round_up
>> could overflow. Can you give a hint please?
> 
> #define round_up(x, y) ((((x)-1) | __round_mask(x, y))+1)
>                                                      ^^^^^
> 
> That +1 can overflow

But that would be a unsigned long long overflow. I considered this to
not be relevant.

> 
> It looks like it would not be so bad to implement some
> check_round_up_overflow() if people prefer
> 
> Jason
>