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Date:   Fri, 31 Jul 2020 07:33:33 +0200
From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     Leon Romanovsky <leon@kernel.org>
Cc:     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,
        netdev@vger.kernel.org, linux-rdma@vger.kernel.org,
        rds-devel@oss.oracle.com, linux-kernel@vger.kernel.org
Subject: Re: [Linux-kernel-mentees] [PATCH net] rds: Prevent kernel-infoleak
 in rds_notify_queue_get()
Message-ID: <20200731053333.GB466103@kroah.com>
References: <20200730192026.110246-1-yepeilin.cs@gmail.com>
 <20200731045301.GI75549@unreal>
 <20200731053306.GA466103@kroah.com>
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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.

And if true, where in the C spec does it say that?

thanks,

greg k-h