On Wed, Mar 28, 2018 at 08:30:37PM +0300, Dan Carpenter wrote:
> On Wed, Mar 28, 2018 at 09:14:25PM +0530, Varun Prakash wrote:
> > On Wed, Mar 21, 2018 at 09:12:00PM -0400, Martin K. Petersen wrote:
> > >
> > > >
> > > > On Wed, Nov 29, 2017 at 02:42:20PM +0300, Dan Carpenter wrote:
> > > >> The story is that Smatch marks skb->data as untrusted and so it
> > > >> complains about this code:
> > > >>
> > > >> drivers/scsi/cxgbi/cxgb4i/cxgb4i.c:2111 t4_uld_rx_handler()
> > > >> error: buffer overflow 'cxgb4i_cplhandlers' 239 <= 255.
> > > >>
> > > >> I don't know the code very well, but it looks like a reasonable warning
> > > >> message. Let's address it by adding a sanity check to make sure "opc"
> > > >> is within bounds.
> > > >>
> > > >> Fixes: bbc02c7e9d34 ("cxgb4: Add register, message, and FW
> > > >> definitions")
> > > >> Signed-off-by: Dan Carpenter <[email protected]>
> > > >>
> > > >> diff --git a/drivers/scsi/cxgbi/cxgb4i/cxgb4i.c
> > > >> b/drivers/scsi/cxgbi/cxgb4i/cxgb4i.c
> > > >> index 266eddf17a99..94b2d5660a07 100644
> > > >> --- a/drivers/scsi/cxgbi/cxgb4i/cxgb4i.c
> > > >> +++ b/drivers/scsi/cxgbi/cxgb4i/cxgb4i.c
> > > >> @@ -2108,12 +2108,12 @@ static int t4_uld_rx_handler(void *handle,
> > > >> const __be64 *rsp,
> > > >> log_debug(1 << CXGBI_DBG_TOE,
> > > >> "cdev %p, opcode 0x%x(0x%x,0x%x), skb %p.\n",
> > > >> cdev, opc, rpl->ot.opcode_tid,
> > > >> ntohl(rpl->ot.opcode_tid), skb);
> > > >> - if (cxgb4i_cplhandlers[opc])
> > > >> - cxgb4i_cplhandlers[opc](cdev, skb);
> > > >> - else {
> > > >> + if (opc >= ARRAY_SIZE(cxgb4i_cplhandlers) ||
> > > >> !cxgb4i_cplhandlers[opc]) {
> > > >> pr_err("No handler for opcode 0x%x.\n", opc);
> > > >> __kfree_skb(skb);
> > > >> + return 0;
> > > >> }
> > > >> + cxgb4i_cplhandlers[opc](cdev, skb);
> > > >> return 0;
> > > >> nomem:
> > > >> log_debug(1 << CXGBI_DBG_TOE, "OOM bailing out.\n");
> > > >
> > > >
> >
> > This check is not necessary but we can add it to avoid warning.
>
> Is the reason it's not necessary, because the skb->data comes from the
> firmware and we trust it?
Yes, opc is an opcode of a cpl cmd which is generated by hardware or firmware,
driver should never get opc >= ARRAY_SIZE(cxgb4i_cplhandler) or
NUM_CPL_CMDS(239).
> The v5 declares the array as having 256
> elements which also solves this warning. And cxgbit_uld_lro_rx_handler()
> has a bounds check. So it seems pretty normal to prevent the array
> overflow by force as well as by trust.
>
> > The commit mentioned in "Fixes" is not correct, this code was added in
> > commit
> > "7b36b6e [SCSI] cxgb4i v5: iscsi driver"
>
> Yeah. You're right. I can resend with an updated commit message.
>
> regards,
> dan carpenter
>
