netdev - Re: [PATCH rdma-next 06/12] RDMA/uverbs: Don't overwrite NULL pointer with ZERO_SIZE

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Message-ID: <20180625080813.GH17747@mtr-leonro.mtl.com>
Date:   Mon, 25 Jun 2018 11:08:13 +0300
From:   Leon Romanovsky <leon@...nel.org>
To:     Jason Gunthorpe <jgg@...pe.ca>
Cc:     Doug Ledford <dledford@...hat.com>,
        RDMA mailing list <linux-rdma@...r.kernel.org>,
        Hadar Hen Zion <hadarh@...lanox.com>,
        Matan Barak <matanb@...lanox.com>,
        Michael J Ruhl <michael.j.ruhl@...el.com>,
        Noa Osherovich <noaos@...lanox.com>,
        Raed Salem <raeds@...lanox.com>,
        Yishai Hadas <yishaih@...lanox.com>,
        Saeed Mahameed <saeedm@...lanox.com>,
        linux-netdev <netdev@...r.kernel.org>
Subject: Re: [PATCH rdma-next 06/12] RDMA/uverbs: Don't overwrite NULL
 pointer with ZERO_SIZE_PTR

On Sun, Jun 24, 2018 at 01:57:51PM -0600, Jason Gunthorpe wrote:
> On Sun, Jun 24, 2018 at 11:23:47AM +0300, Leon Romanovsky wrote:
> > From: Leon Romanovsky <leonro@...lanox.com>
> >
> > Number of specs is provided by user and in valid case can be equal to zero.
> > Such argument causes to call to kcalloc() with zero-length request and in
> > return the ZERO_SIZE_PTR is assigned. This pointer is different from NULL
> > and makes various if (..) checks to success.
>
> The one seems really weird. There is nothing wrong with ZERO_SIZE_PTR,
> but this description and fix suggest that something did
>
> ptr = kalloc(0);
> ptr[0] = ...;
>
> Which is not allowed of course. Doesn't this mean there is also a
> missing range check someplace?

I don't know, this issue was found during code review of
ib_uvrebs_ex_create_flow(), may or may not be real issue.

Thanks

>
> Jason

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