On Sat, Apr 27, 2024 at 12:23 PM Dmitry Baryshkov
<dmitry.baryshkov@xxxxxxxxxx> wrote:
>
> On Sat, Apr 27, 2024 at 05:50:10PM +0000, Badhri Jagan Sridharan wrote:
> > typec_register_partner() does not guarantee partner registration
> > to always succeed. In the event of failure, port->partner is set
> > to the error value or NULL. Given that port->partner validity is
> > not checked, this results in the following crash:
> >
> > [17514.377076][ T275] Unable to handle kernel NULL pointer dereference at virtual address 00000000000003c0
> > [17514.378270][ T275] pc : run_state_machine+0x1bc8/0x1c08
> > [17514.378286][ T275] lr : run_state_machine+0x1b90/0x1c08
> > ..
> > [17514.378377][ T275] Call trace:
> > [17514.378381][ T275] run_state_machine+0x1bc8/0x1c08
> > [17514.378388][ T275] tcpm_state_machine_work+0x94/0xe4
> > [17514.378396][ T275] kthread_worker_fn+0x118/0x328
> > [17514.378406][ T275] kthread+0x1d0/0x23c
> > [17514.378412][ T275] ret_from_fork+0x10/0x20
>
> Nit: thre is little use in the timestamps and the T275 tag. In future
> patches you can safely ommit such data.
>
> >
> > To prevent the crash, check for port->partner validity before
> > derefencing it in all the call sites.
> >
> > Cc: stable@xxxxxxxxxxxxxxx
> > Fixes: c97cd0b4b54e ("usb: typec: tcpm: set initial svdm version based on pd revision")
> > Signed-off-by: Badhri Jagan Sridharan <badhri@xxxxxxxxxx>
> > ---
> > drivers/usb/typec/tcpm/tcpm.c | 19 ++++++++++++++-----
> > 1 file changed, 14 insertions(+), 5 deletions(-)
> >
> > diff --git a/drivers/usb/typec/tcpm/tcpm.c b/drivers/usb/typec/tcpm/tcpm.c
> > index ab6ed6111ed0..8a4fa8d875c6 100644
> > --- a/drivers/usb/typec/tcpm/tcpm.c
> > +++ b/drivers/usb/typec/tcpm/tcpm.c
> > @@ -4,7 +4,6 @@
> > *
> > * USB Power Delivery protocol stack.
> > */
> > -
> > #include <linux/completion.h>
> > #include <linux/debugfs.h>
> > #include <linux/device.h>
> > @@ -1580,7 +1579,8 @@ static void svdm_consume_identity(struct tcpm_port *port, const u32 *p, int cnt)
> > port->partner_ident.cert_stat = p[VDO_INDEX_CSTAT];
> > port->partner_ident.product = product;
> >
> > - typec_partner_set_identity(port->partner);
> > + if (!IS_ERR_OR_NULL(port->partner))
>
> I think that it might be better to check typec_register_partner() result
> in tcpm_typec_connect() and skip setting port->partner in case it
> returned an error (an error message would be also beneficial).
> See for example, how this is handled in ucsi_register_partner().
>
> Then these checks can be turned into simple `if (port->partner)`.
Sounds good ! However, I was wondering whether the error message is
redundant as typec_register_partner() also prints one. I have anyways
added that in V3.
Thanks,
Badhri
>
> > + typec_partner_set_identity(port->partner);
> >
> > tcpm_log(port, "Identity: %04x:%04x.%04x",
> > PD_IDH_VID(vdo),
> > @@ -1742,6 +1742,9 @@ static void tcpm_register_partner_altmodes(struct tcpm_port *port)
> > struct typec_altmode *altmode;
> > int i;
> >
> > + if (IS_ERR_OR_NULL(port->partner))
> > + return;
> > +
> > for (i = 0; i < modep->altmodes; i++) {
> > altmode = typec_partner_register_altmode(port->partner,
> > &modep->altmode_desc[i]);
> > @@ -4244,7 +4247,8 @@ static void tcpm_typec_connect(struct tcpm_port *port)
> > port->partner = typec_register_partner(port->typec_port,
> > &port->partner_desc);
> > port->connected = true;
> > - typec_partner_set_usb_power_delivery(port->partner, port->partner_pd);
> > + if (!IS_ERR_OR_NULL(port->partner))
> > + typec_partner_set_usb_power_delivery(port->partner, port->partner_pd);
> > }
> > }
> >
> > @@ -4323,8 +4327,10 @@ static void tcpm_typec_disconnect(struct tcpm_port *port)
> > port->plug_prime = NULL;
> > port->cable = NULL;
> > if (port->connected) {
> > - typec_partner_set_usb_power_delivery(port->partner, NULL);
> > - typec_unregister_partner(port->partner);
> > + if (!IS_ERR_OR_NULL(port->partner)) {
> > + typec_partner_set_usb_power_delivery(port->partner, NULL);
> > + typec_unregister_partner(port->partner);
> > + }
> > port->partner = NULL;
> > port->connected = false;
> > }
> > @@ -4549,6 +4555,9 @@ static enum typec_cc_status tcpm_pwr_opmode_to_rp(enum typec_pwr_opmode opmode)
> >
> > static void tcpm_set_initial_svdm_version(struct tcpm_port *port)
> > {
> > + if (IS_ERR_OR_NULL(port->partner))
> > + return;
> > +
> > switch (port->negotiated_rev) {
> > case PD_REV30:
> > break;
> >
> > base-commit: 3f12222a4bebeb13ce06ddecc1610ad32fa835dd
> > --
> > 2.44.0.769.g3c40516874-goog
> >
>
> --
> With best wishes
> Dmitry
