linux-kernel - Re: [patch] VMCI: integer overflow in vmci_datagram

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Date:	Fri, 29 Aug 2014 14:21:04 +0300
From:	Dan Carpenter <dan.carpenter@...cle.com>
To:	walter harms <wharms@....de>
Cc:	linux-kernel@...r.kernel.org,
	George Zhang <georgezhang@...are.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	kernel-janitors@...r.kernel.org
Subject: Re: [patch] VMCI: integer overflow in vmci_datagram_dispatch()

On Fri, Aug 29, 2014 at 01:13:47PM +0200, walter harms wrote:
> 
> 
> Am 29.08.2014 10:42, schrieb Dan Carpenter:
> > This is untrusted user data from vmci_host_do_send_datagram() so the
> > VMCI_DG_SIZE() macro can have an integer overflow.
> > 
> > Signed-off-by: Dan Carpenter <dan.carpenter@...cle.com>
> > 
> > diff --git a/drivers/misc/vmw_vmci/vmci_datagram.c b/drivers/misc/vmw_vmci/vmci_datagram.c
> > index f3cdd90..8226652 100644
> > --- a/drivers/misc/vmw_vmci/vmci_datagram.c
> > +++ b/drivers/misc/vmw_vmci/vmci_datagram.c
> > @@ -328,7 +328,8 @@ int vmci_datagram_dispatch(u32 context_id,
> >  
> >  	BUILD_BUG_ON(sizeof(struct vmci_datagram) != 24);
> >  
> > -	if (VMCI_DG_SIZE(dg) > VMCI_MAX_DG_SIZE) {
> > +	if (dg->payload_size > VMCI_MAX_DG_SIZE ||
> > +	    VMCI_DG_SIZE(dg) > VMCI_MAX_DG_SIZE) {
> >  		pr_devel("Payload (size=%llu bytes) too big to send\n",
> >  			 (unsigned long long)dg->payload_size);
> >  		return VMCI_ERROR_INVALID_ARGS;
> 
> Are your sure about that ">" ? maybe ">=" was intended ?

Yes, I'm sure.  As a rule of thumb, > is used for size comparisons and
>= is used for index comparisons.

regards,
dan carpenter

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