Re: [PATCH] net: bnxt: fix a potential use-after-free in bnxt_init_tc

[Michael Chan]

On Mon, Dec 4, 2023 at 12:56 AM Pavan Chebbi <pavan.chebbi@xxxxxxxxxxxx> wrote:
>
> On Mon, Dec 4, 2023 at 8:11 AM Dinghao Liu <dinghao.liu@xxxxxxxxxx> wrote:
> >
> > When flow_indr_dev_register() fails, bnxt_init_tc will free
> > bp->tc_info through kfree(). However, the caller function
> > bnxt_init_one() will ignore this failure and call
> > bnxt_shutdown_tc() on failure of bnxt_dl_register(), where
> > a use-after-free happens. Fix this issue by setting
> > bp->tc_info to NULL after kfree().
> >
> > Fixes: 627c89d00fb9 ("bnxt_en: flow_offload: offload tunnel decap rules via indirect callbacks")
> > Signed-off-by: Dinghao Liu <dinghao.liu@xxxxxxxxxx>
> > ---
> >  drivers/net/ethernet/broadcom/bnxt/bnxt_tc.c | 1 +
> >  1 file changed, 1 insertion(+)
> >
> > diff --git a/drivers/net/ethernet/broadcom/bnxt/bnxt_tc.c b/drivers/net/ethernet/broadcom/bnxt/bnxt_tc.c
> > index 38d89d80b4a9..273c9ba48f09 100644
> > --- a/drivers/net/ethernet/broadcom/bnxt/bnxt_tc.c
> > +++ b/drivers/net/ethernet/broadcom/bnxt/bnxt_tc.c
> > @@ -2075,6 +2075,7 @@ int bnxt_init_tc(struct bnxt *bp)
> >         rhashtable_destroy(&tc_info->flow_table);
> >  free_tc_info:
> >         kfree(tc_info);
> > +       bp->tc_info = NULL;
> >         return rc;
> >  }
>
> The other way could have been to assign bp->tc_info only after
> flow_indr_dev_register succeeds.
> But this one works too. Thanks.
> Reviewed-by: Pavan Chebbi <pavan.chebbi@xxxxxxxxxxxx>

I think this is the correct fix.  flow_indr_dev_register(), if
successful, may call the driver's call back function and so
bp->tc_info must be set up before the call.  Thanks.

Reviewed-by: Michael Chan <michael.chan@xxxxxxxxxxxx>

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