linux-kernel - Re: [PATCH v2] RDMA: Directly cast the sockaddr union to sockaddr

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Message-ID: <20190517113230.6sx5amsm3vsji2mz@verge.net.au>
Date:   Fri, 17 May 2019 13:32:30 +0200
From:   Simon Horman <horms@...ge.net.au>
To:     Jason Gunthorpe <jgg@...pe.ca>
Cc:     Linus Torvalds <torvalds@...ux-foundation.org>,
        David Miller <davem@...emloft.net>,
        Doug Ledford <dledford@...hat.com>,
        linux-rdma <linux-rdma@...r.kernel.org>,
        Linux List Kernel Mailing <linux-kernel@...r.kernel.org>,
        Netdev <netdev@...r.kernel.org>
Subject: Re: [PATCH v2] RDMA: Directly cast the sockaddr union to sockaddr

On Thu, May 16, 2019 at 12:21:48PM -0300, Jason Gunthorpe wrote:
> On Thu, May 16, 2019 at 02:44:28PM +0200, Simon Horman wrote:
> > On Mon, May 13, 2019 at 09:55:21PM -0300, Jason Gunthorpe wrote:
> > > gcc 9 now does allocation size tracking and thinks that passing the member
> > > of a union and then accessing beyond that member's bounds is an overflow.
> > > 
> > > Instead of using the union member, use the entire union with a cast to
> > > get to the sockaddr. gcc will now know that the memory extends the full
> > > size of the union.
> > > 
> > > Signed-off-by: Jason Gunthorpe <jgg@...lanox.com>
> > >  drivers/infiniband/core/addr.c           | 16 ++++++++--------
> > >  drivers/infiniband/hw/ocrdma/ocrdma_ah.c |  5 ++---
> > >  drivers/infiniband/hw/ocrdma/ocrdma_hw.c |  5 ++---
> > >  3 files changed, 12 insertions(+), 14 deletions(-)
> > > 
> > > I missed the ocrdma files in the v1
> > > 
> > > We can revisit what to do with that repetitive union after the merge
> > > window, but this simple patch will eliminate the warnings for now.
> > > 
> > > Linus, I'll send this as a PR tomorrow - there is also a bug fix for
> > > the rdma-netlink changes posted that should go too.
> > 
> > <2c>
> > I would be very happy to see this revisited in such a way
> > that some use is made of the C type system (instead of casts).
> > </2c>
> 
> Well, I was thinking of swapping the union to sockaddr_storage ..
> 
> Do you propose to add a union to the kernel's sockaddr storage?

I understand you have been down that rabbit hole before but,
yes, in an ideal world that would be my preference.