linux-kernel - Re: [PATCH] scsi: ses: Fix out-of-bounds memory access in ses_enclosure_data

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Date:   Mon, 20 May 2019 08:46:52 -0700
From:   James Bottomley <jejb@...ux.ibm.com>
To:     Waiman Long <longman@...hat.com>,
        "Martin K. Petersen" <martin.petersen@...cle.com>
Cc:     linux-scsi@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] scsi: ses: Fix out-of-bounds memory access in
 ses_enclosure_data_process()

On Mon, 2019-05-20 at 11:24 -0400, Waiman Long wrote:
> On 5/20/19 10:52 AM, James Bottomley wrote:
> > On Mon, 2019-05-20 at 10:41 -0400, Waiman Long wrote:
> > [...]
> > > > --- a/drivers/scsi/ses.c
> > > > +++ b/drivers/scsi/ses.c
> > > > @@ -605,9 +605,14 @@ static void
> > > > ses_enclosure_data_process(struct
> > > > enclosure_device *edev,
> > > >  			     /* these elements are optional */
> > > >  			     type_ptr[0] ==
> > > > ENCLOSURE_COMPONENT_SCSI_TARGET_PORT ||
> > > >  			     type_ptr[0] ==
> > > > ENCLOSURE_COMPONENT_SCSI_INITIATOR_PORT ||
> > > > -			     type_ptr[0] ==
> > > > ENCLOSURE_COMPONENT_CONTROLLER_ELECTRONICS))
> > > > +			     type_ptr[0] ==
> > > > ENCLOSURE_COMPONENT_CONTROLLER_ELECTRONICS)) {
> > > >  				addl_desc_ptr +=
> > > > addl_desc_ptr[1]
> > > > + 2;
> > > >  
> > > > +				/* Ensure no out-of-bounds
> > > > memory
> > > > access */
> > > > +				if (addl_desc_ptr >= ses_dev-
> > > > > page10 +
> > > > 
> > > > +						     ses_dev-
> > > > > page10_len)
> > > > 
> > > > +					addl_desc_ptr = NULL;
> > > > +			}
> > > >  		}
> > > >  	}
> > > >  	kfree(buf);
> > > 
> > > Ping! Any comment on this patch.
> > 
> > The update looks fine to me:
> > 
> > Reviewed-by: James E.J. Bottomley <jejb@...ux.ibm.com>
> > 
> > It might also be interesting to find out how the proliant is
> > structuring this descriptor array to precipitate the out of bounds:
> > Is it just an off by one or something more serious?
> 
> I didn't look into the detail the enclosure message returned by the
> hardware, but I believe it may have more description entries (page7)
> than extended description entries (page10).
> 
> I can try to reserve the system and find out what exactly is wrong
> with that system if you really want to find that out.

Please.  What I'm interested in is whether this is simply a bug in the
array firmware, in which case the fix is sufficient, or whether there's
some problem with the parser, like mismatched expectations over added
trailing nulls or something.

James