linux-kernel - Re: [RFC PATCH v1 42/50] drivers/ininiband: Use get_random

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Message-ID: <20200329143621.GF20941@ziepe.ca>
Date:   Sun, 29 Mar 2020 11:36:21 -0300
From:   Jason Gunthorpe <jgg@...pe.ca>
To:     George Spelvin <lkml@....org>
Cc:     linux-kernel@...r.kernel.org, Doug Ledford <dledford@...hat.com>,
        linux-rdma@...r.kernel.org, Faisal Latif <faisal.latif@...el.com>,
        Shiraz Saleem <shiraz.saleem@...el.com>,
        Bart Van Assche <bvanassche@....org>,
        Bernard Metzler <bmt@...ich.ibm.com>
Subject: Re: [RFC PATCH v1 42/50] drivers/ininiband: Use get_random_u32()

On Wed, Aug 21, 2019 at 08:21:45PM -0400, George Spelvin wrote:
> There's no need to get_random_bytes() into a temporary buffer.
> 
> This is not a no-brainer change; get_random_u32() has slightly weaker
> security guarantees, but code like this is the classic example of when
> it's appropriate: the random value is stored in the kernel for as long
> as it's valuable.

The mechanical transformation looks OK, but can someone who knows the
RNG confirm this statement?

Many of these places are being used in network related contexts, I
suspect the value here is often less about secrecy, more about
unguessability.

Jason