From: Kees Cook <keescook@chromium.org>
To: Leon Romanovsky <leon@kernel.org>
Cc: Jack Morgenstein <jackm@nvidia.com>,
Jason Gunthorpe <jgg@ziepe.ca>, Yishai Hadas <yishaih@nvidia.com>,
Doug Ledford <dledford@redhat.com>,
linux-kernel@vger.kernel.org, linux-rdma@vger.kernel.org,
linux-hardening@vger.kernel.org
Subject: Re: [PATCH] IB/mlx4: Avoid field-overflowing memcpy()
Date: Thu, 17 Jun 2021 12:46:43 -0700 [thread overview]
Message-ID: <202106171239.C425161E8@keescook> (raw)
In-Reply-To: <YMr4ypsh7D3q1R5+@unreal>
On Thu, Jun 17, 2021 at 10:24:58AM +0300, Leon Romanovsky wrote:
> On Wed, Jun 16, 2021 at 01:37:44PM -0700, Kees Cook wrote:
> > In preparation for FORTIFY_SOURCE performing compile-time and run-time
> > field bounds checking for memcpy(), memmove(), and memset(), avoid
> > intentionally writing across neighboring array fields.
> >
> > Use the ether_addr_copy() helper instead, as already done for smac.
> >
> > Signed-off-by: Kees Cook <keescook@chromium.org>
> > ---
> > drivers/infiniband/hw/mlx4/qp.c | 2 +-
> > 1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/drivers/infiniband/hw/mlx4/qp.c b/drivers/infiniband/hw/mlx4/qp.c
> > index 2ae22bf50016..4a2ef7daaded 100644
> > --- a/drivers/infiniband/hw/mlx4/qp.c
> > +++ b/drivers/infiniband/hw/mlx4/qp.c
> > @@ -3144,7 +3144,7 @@ static int build_mlx_header(struct mlx4_ib_qp *qp, const struct ib_ud_wr *wr,
> > mlx->sched_prio = cpu_to_be16(pcp);
> >
> > ether_addr_copy(sqp->ud_header.eth.smac_h, ah->av.eth.s_mac);
> > - memcpy(sqp->ud_header.eth.dmac_h, ah->av.eth.mac, 6);
> > + ether_addr_copy(sqp->ud_header.eth.dmac_h, ah->av.eth.mac);
> > memcpy(&ctrl->srcrb_flags16[0], ah->av.eth.mac, 2);
> > memcpy(&ctrl->imm, ah->av.eth.mac + 2, 4);
>
> I don't understand the last three lines. We are copying 6 bytes to
> ah->av.eth.mac and immediately after that overwriting them.
I'm not following (the memcpy() is replaced by ether_addr_copy()). I only
see ah->av.eth.mac being read from (not written to). And the destinations
are {s,d}mac_h:
ah->av.eth.s_mac -> sqp->ud_header.eth.smac_h (s_mac to smac_h: 6 bytes)
ah->av.eth.mac -> sqp->ud_header.eth.dmac_h (mac to dmac_h: 6 bytes)
after that I see:
ah->av.eth.mac -> &ctrl->srcrb_flags16[0] (2 bytes)
ah->av.eth.mac + 2 -> ctrl->imm (4 bytes)
The last two copies mac again in pieces, but I don't know what any of
this is actually used for, which I what I assume you're asking about. :)
> Jack,
>
> Do you remember what you wanted to achieve in commit
> 6ee51a4e866b ("mlx4: Adjust QP1 multiplexing for RoCE/SRIOV")
>
> Thanks
-Kees
--
Kees Cook
next prev parent reply other threads:[~2021-06-17 19:46 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-06-16 20:37 [PATCH] IB/mlx4: Avoid field-overflowing memcpy() Kees Cook
2021-06-17 7:24 ` Leon Romanovsky
2021-06-17 19:46 ` Kees Cook [this message]
2021-06-21 8:11 ` Leon Romanovsky
2021-06-22 0:05 ` Jason Gunthorpe
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