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From: Leon Romanovsky <leon@kernel.org>
To: Andy Shevchenko <andy.shevchenko@gmail.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Peilin Ye <yepeilin.cs@gmail.com>,
	Santosh Shilimkar <santosh.shilimkar@oracle.com>,
	"David S. Miller" <davem@davemloft.net>,
	Jakub Kicinski <kuba@kernel.org>,
	Dan Carpenter <dan.carpenter@oracle.com>,
	Arnd Bergmann <arnd@arndb.de>,
	"linux-kernel-mentees@lists.linuxfoundation.org" 
	<linux-kernel-mentees@lists.linuxfoundation.org>,
	"netdev@vger.kernel.org" <netdev@vger.kernel.org>,
	"linux-rdma@vger.kernel.org" <linux-rdma@vger.kernel.org>,
	"rds-devel@oss.oracle.com" <rds-devel@oss.oracle.com>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: [Linux-kernel-mentees] [PATCH net] rds: Prevent kernel-infoleak in rds_notify_queue_get()
Date: Fri, 31 Jul 2020 10:00:30 +0300
Message-ID: <20200731070030.GJ75549@unreal> (raw)
In-Reply-To: <CAHp75Vdr2HC_ogNhBCxxGut9=Z6pQMFiA0w-268OQv+5unYOTg@mail.gmail.com>

On Fri, Jul 31, 2020 at 09:29:27AM +0300, Andy Shevchenko wrote:
> On Friday, July 31, 2020, Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> wrote:
>
> > On Fri, Jul 31, 2020 at 07:33:06AM +0200, Greg Kroah-Hartman wrote:
> > > On Fri, Jul 31, 2020 at 07:53:01AM +0300, Leon Romanovsky wrote:
> > > > On Thu, Jul 30, 2020 at 03:20:26PM -0400, Peilin Ye wrote:
> > > > > rds_notify_queue_get() is potentially copying uninitialized kernel
> > stack
> > > > > memory to userspace since the compiler may leave a 4-byte hole at
> > the end
> > > > > of `cmsg`.
> > > > >
> > > > > In 2016 we tried to fix this issue by doing `= { 0 };` on `cmsg`,
> > which
> > > > > unfortunately does not always initialize that 4-byte hole. Fix it by
> > using
> > > > > memset() instead.
> > > >
> > > > Of course, this is the difference between "{ 0 }" and "{}"
> > initializations.
> > >
> > > Really?  Neither will handle structures with holes in it, try it and
> > > see.
>
>
> {} is a GCC extension, but I never thought it works differently.

Yes, this is GCC extension and kernel relies on them very heavily.

Thanks

>
>
>
> >
> > And if true, where in the C spec does it say that?
> >
> > thanks,
> >
> > greg k-h
> >
>
>
> --
> With Best Regards,
> Andy Shevchenko

  parent reply index

Thread overview: 30+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-07-30 19:20 Peilin Ye
2020-07-30 19:29 ` santosh.shilimkar
2020-07-31  4:53 ` Leon Romanovsky
2020-07-31  5:33   ` Greg Kroah-Hartman
2020-07-31  5:33     ` Greg Kroah-Hartman
     [not found]       ` <CAHp75Vdr2HC_ogNhBCxxGut9=Z6pQMFiA0w-268OQv+5unYOTg@mail.gmail.com>
2020-07-31  7:00         ` Leon Romanovsky [this message]
2020-07-31  7:05           ` Andy Shevchenko
2020-07-31 14:04       ` Jason Gunthorpe
2020-07-31 14:21         ` Greg Kroah-Hartman
2020-07-31 14:36           ` Jason Gunthorpe
2020-07-31 17:19             ` Greg Kroah-Hartman
2020-07-31 18:27               ` Jason Gunthorpe
2020-08-01  8:00                 ` Dan Carpenter
2020-08-01 14:40                   ` Jason Gunthorpe
2020-08-03  9:34                     ` Dan Carpenter
2020-08-01  5:38               ` Leon Romanovsky
2020-08-02 22:10                 ` Jason Gunthorpe
2020-08-02 22:23                   ` Joe Perches
2020-08-02 22:28                     ` Jason Gunthorpe
2020-08-02 22:45                       ` Joe Perches
2020-08-03  4:58                         ` Leon Romanovsky
2020-08-03 23:06                         ` Jason Gunthorpe
2020-08-08 22:57                           ` Jack Leadford
2020-08-09  7:04                             ` Leon Romanovsky
2020-08-14 17:07                             ` Jason Gunthorpe
2020-07-31  9:59   ` Dan Carpenter
2020-07-31 11:14     ` Håkon Bugge
2020-07-31 11:59       ` Greg Kroah-Hartman
2020-07-31 12:03         ` Håkon Bugge
2020-07-31 23:54 ` David Miller

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