Re: [PATCH 2/3] scsi: libiscsi: fix invalid pointer dereference in iscsi_eh_session_reset

[Ding Hui]

On 2021/9/11 12:38 上午, Mike Christie wrote:
> On 9/9/21 8:02 PM, Ding Hui wrote:
> > like commit 5db6dd14b313 ("scsi: libiscsi: Fix NULL pointer dereference in
> > iscsi_eh_session_reset"), access conn->persistent_address here is not safe
> > too.
> >
> > The persistent_address is independent of conn refcount, so maybe
> > already freed by iscsi_conn_teardown(), also we put the refcount of conn
> > above, the conn pointer may be invalid.
>
> This shouldn't happen like you describe above, because when we wake up
> we will see the session->state is ISCSI_STATE_TERMINATE. We will then
> not reference the conn in that code below.
>
> However, it looks like we could hit an issue where if a user was resetting
> the persistent_address or targetname via iscsi_set_param -> iscsi_switch_str_param
> then we could be accessing freed memory. I think we need the frwd_lock when swapping
> the strings in iscsi_switch_str_param.

Thanks for your detailed explanation, I'll drop 2/3 and 3/3 in v2 patch.
I expect that the persistent_address issue be fixed in your future patchset.

Sorry for my ignorance.

> > Signed-off-by: Ding Hui <dinghui@xxxxxxxxxxxxxx>
> > ---
> >   drivers/scsi/libiscsi.c | 4 ++--
> >   1 file changed, 2 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/scsi/libiscsi.c b/drivers/scsi/libiscsi.c
> > index 712a45368385..69b3b2148328 100644
> > --- a/drivers/scsi/libiscsi.c
> > +++ b/drivers/scsi/libiscsi.c
> > @@ -2531,8 +2531,8 @@ int iscsi_eh_session_reset(struct scsi_cmnd *sc)
> >   	spin_lock_bh(&session->frwd_lock);
> >   	if (session->state == ISCSI_STATE_LOGGED_IN) {
> >   		ISCSI_DBG_EH(session,
> > -			     "session reset succeeded for %s,%s\n",
> > -			     session->targetname, conn->persistent_address);
> > +			     "session reset succeeded for %s\n",
> > +			     session->targetname);
> >   	} else
> >   		goto failed;
> >   	spin_unlock_bh(&session->frwd_lock);


--
Thanks,
-dinghui