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Subject[PATCH v2] usb: typec: tcpm: Ignore unsupported/unknown alternate mode requests
Date
TCPM may receive PD messages associated with unknown or unsupported
alternate modes. If that happens, calls to typec_match_altmode()
will return NULL. The tcpm code does not currently take this into
account. This results in crashes.

Unable to handle kernel NULL pointer dereference at virtual address 000001f0
pgd = 41dad9a1
[000001f0] *pgd=00000000
Internal error: Oops: 5 [#1] THUMB2
Modules linked in: tcpci tcpm
CPU: 0 PID: 2338 Comm: kworker/u2:0 Not tainted 5.1.18-sama5-armv7-r2 #6
Hardware name: Atmel SAMA5
Workqueue: 2-0050 tcpm_pd_rx_handler [tcpm]
PC is at typec_altmode_attention+0x0/0x14
LR is at tcpm_pd_rx_handler+0xa3b/0xda0 [tcpm]
...
[<c03fbee8>] (typec_altmode_attention) from [<bf8030fb>]
(tcpm_pd_rx_handler+0xa3b/0xda0 [tcpm])
[<bf8030fb>] (tcpm_pd_rx_handler [tcpm]) from [<c012082b>]
(process_one_work+0x123/0x2a8)
[<c012082b>] (process_one_work) from [<c0120a6d>]
(worker_thread+0xbd/0x3b0)
[<c0120a6d>] (worker_thread) from [<c012431f>] (kthread+0xcf/0xf4)
[<c012431f>] (kthread) from [<c01010f9>] (ret_from_fork+0x11/0x38)

Ignore PD messages if the associated alternate mode is not supported.

Fixes: e9576fe8e605c ("usb: typec: tcpm: Support for Alternate Modes")
Reported-by: Douglas Gilbert <dgilbert@interlog.com>
Cc: Douglas Gilbert <dgilbert@interlog.com>
Acked-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Tested-by: Douglas Gilbert <dgilbert@interlog.com>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
---
v2: No functional change
Dropped RFC
Added Tested/by: / Acked-by: tags

drivers/usb/typec/tcpm/tcpm.c | 38 ++++++++++++++++++++++++--------------
1 file changed, 24 insertions(+), 14 deletions(-)

diff --git a/drivers/usb/typec/tcpm/tcpm.c b/drivers/usb/typec/tcpm/tcpm.c
index 77f71f602f73..1df2844469aa 100644
--- a/drivers/usb/typec/tcpm/tcpm.c
+++ b/drivers/usb/typec/tcpm/tcpm.c
@@ -1096,7 +1096,8 @@ static int tcpm_pd_svdm(struct tcpm_port *port, const __le32 *payload, int cnt,
break;
case CMD_ATTENTION:
/* Attention command does not have response */
- typec_altmode_attention(adev, p[1]);
+ if (adev)
+ typec_altmode_attention(adev, p[1]);
return 0;
default:
break;
@@ -1148,20 +1149,26 @@ static int tcpm_pd_svdm(struct tcpm_port *port, const __le32 *payload, int cnt,
}
break;
case CMD_ENTER_MODE:
- typec_altmode_update_active(pdev, true);
-
- if (typec_altmode_vdm(adev, p[0], &p[1], cnt)) {
- response[0] = VDO(adev->svid, 1, CMD_EXIT_MODE);
- response[0] |= VDO_OPOS(adev->mode);
- return 1;
+ if (adev && pdev) {
+ typec_altmode_update_active(pdev, true);
+
+ if (typec_altmode_vdm(adev, p[0], &p[1], cnt)) {
+ response[0] = VDO(adev->svid, 1,
+ CMD_EXIT_MODE);
+ response[0] |= VDO_OPOS(adev->mode);
+ return 1;
+ }
}
return 0;
case CMD_EXIT_MODE:
- typec_altmode_update_active(pdev, false);
+ if (adev && pdev) {
+ typec_altmode_update_active(pdev, false);

- /* Back to USB Operation */
- WARN_ON(typec_altmode_notify(adev, TYPEC_STATE_USB,
- NULL));
+ /* Back to USB Operation */
+ WARN_ON(typec_altmode_notify(adev,
+ TYPEC_STATE_USB,
+ NULL));
+ }
break;
default:
break;
@@ -1171,8 +1178,10 @@ static int tcpm_pd_svdm(struct tcpm_port *port, const __le32 *payload, int cnt,
switch (cmd) {
case CMD_ENTER_MODE:
/* Back to USB Operation */
- WARN_ON(typec_altmode_notify(adev, TYPEC_STATE_USB,
- NULL));
+ if (adev)
+ WARN_ON(typec_altmode_notify(adev,
+ TYPEC_STATE_USB,
+ NULL));
break;
default:
break;
@@ -1183,7 +1192,8 @@ static int tcpm_pd_svdm(struct tcpm_port *port, const __le32 *payload, int cnt,
}

/* Informing the alternate mode drivers about everything */
- typec_altmode_vdm(adev, p[0], &p[1], cnt);
+ if (adev)
+ typec_altmode_vdm(adev, p[0], &p[1], cnt);

return rlen;
}
--
2.7.4
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