linux-kernel - Re: [PATCH 10/18] qla2xxx: prevent bounds-check bypass via speculative execution

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Message-ID: <20180106090322.GF4380@kroah.com>
Date:   Sat, 6 Jan 2018 10:03:22 +0100
From:   Greg KH <gregkh@...uxfoundation.org>
To:     Dan Williams <dan.j.williams@...el.com>
Cc:     linux-kernel@...r.kernel.org, linux-arch@...r.kernel.org,
        "James E.J. Bottomley" <jejb@...ux.vnet.ibm.com>,
        "Martin K. Petersen" <martin.petersen@...cle.com>,
        linux-scsi@...r.kernel.org, peterz@...radead.org,
        netdev@...r.kernel.org, qla2xxx-upstream@...gic.com,
        tglx@...utronix.de, torvalds@...ux-foundation.org,
        Elena Reshetova <elena.reshetova@...el.com>,
        alan@...ux.intel.com
Subject: Re: [PATCH 10/18] qla2xxx: prevent bounds-check bypass via
 speculative execution

On Fri, Jan 05, 2018 at 05:10:48PM -0800, Dan Williams wrote:
> Static analysis reports that 'handle' may be a user controlled value
> that is used as a data dependency to read 'sp' from the
> 'req->outstanding_cmds' array.  In order to avoid potential leaks of
> kernel memory values, block speculative execution of the instruction
> stream that could issue reads based on an invalid value of 'sp'. In this
> case 'sp' is directly dereferenced later in the function.

I'm pretty sure that 'handle' comes from the hardware, not from
userspace, from what I can tell here.  If we want to start auditing
__iomem data sources, great!  But that's a bigger task, and one I don't
think we are ready to tackle...

thanks,

greg k-h